698 lines
		
	
	
		
			23 KiB
		
	
	
	
		
			ReStructuredText
		
	
	
	
			
		
		
	
	
			698 lines
		
	
	
		
			23 KiB
		
	
	
	
		
			ReStructuredText
		
	
	
	
| .. SPDX-License-Identifier: GPL-2.0+
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| .. Copyright (C) 2020 Sean Anderson <seanga2@gmail.com>
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| 
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| MAIX
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| ====
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| 
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| Several of the Sipeed Maix series of boards contain the Kendryte K210 processor,
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| a 64-bit RISC-V CPU produced by Canaan Inc. This processor contains several
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| peripherals to accelerate neural network processing and other "ai" tasks. This
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| includes a "KPU" neural network processor, an audio processor supporting
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| beamforming reception, and a digital video port supporting capture and output at
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| VGA resolution. Other peripherals include 8M of SRAM (accessible with and
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| without caching); remappable pins, including 40 GPIOs; AES, FFT, and SHA256
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| accelerators; a DMA controller; and I2C, I2S, and SPI controllers. Maix
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| peripherals vary, but include spi flash; on-board usb-serial bridges; ports for
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| cameras, displays, and sd cards; and ESP32 chips.
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| 
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| Currently, only the Sipeed MAIX BiT V2.0 (bitm) and Sipeed MAIXDUINO are
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| supported, but the boards are fairly similar.
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| 
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| Documentation for Maix boards is available from
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| `Sipeed's website <http://dl.sipeed.com/MAIX/HDK/>`_.
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| Documentation for the Kendryte K210 is available from
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| `Kendryte's website <https://kendryte.com/downloads/>`_. However, hardware
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| details are rather lacking, so most technical reference has been taken from the
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| `standalone sdk <https://github.com/kendryte/kendryte-standalone-sdk>`_.
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| 
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| Build and boot steps
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| --------------------
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| 
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| To build U-Boot, run
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| 
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| .. code-block:: none
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| 
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|     make <defconfig>
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|     make CROSS_COMPILE=<your cross compile prefix>
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| 
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| To flash U-Boot, run
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| 
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| .. code-block:: none
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| 
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|     kflash -tp /dev/<your tty here> -B <board_id> u-boot-dtb.bin
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| 
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| The board provides two serial devices, e.g.
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| 
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| * /dev/serial/by-id/usb-Kongou_Hikari_Sipeed-Debug_12345678AB-if00-port0
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| * /dev/serial/by-id/usb-Kongou_Hikari_Sipeed-Debug_12345678AB-if01-port0
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| 
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| Which one is used for flashing depends on the board.
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| 
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| Currently only a small subset of the board features are supported. So we can
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| use the same default configuration and device tree. In the long run we may need
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| separate settings.
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| 
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| ======================== ========================== ========== ==========
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| Board                    defconfig                  board_id   TTY device
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| ======================== ========================== ========== ==========
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| Sipeed MAIX BiT          sipeed_maix_bitm_defconfig bit        first
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| Sipeed MAIX BiT with Mic sipeed_maix_bitm_defconfig bit_mic    first
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| Sipeed MAIXDUINO         sipeed_maix_bitm_defconfig maixduino  first
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| Sipeed MAIX GO                                      goE        second
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| Sipeed MAIX ONE DOCK                                dan        first
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| ======================== ========================== ========== ==========
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| 
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| Flashing causes a reboot of the device. Parameter -t specifies that the serial
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| console shall be opened immediately. Boot output should look like the following:
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| 
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| .. code-block:: none
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| 
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|     U-Boot 2020.04-rc2-00087-g2221cc09c1-dirty (Feb 28 2020 - 13:53:09 -0500)
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| 
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|     DRAM:  8 MiB
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|     MMC:   spi@53000000:slot@0: 0
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|     In:    serial@38000000
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|     Out:   serial@38000000
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|     Err:   serial@38000000
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|     =>
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| 
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| OpenSBI
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| ^^^^^^^
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| 
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| OpenSBI is an open source supervisor execution environment implementing the
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| RISC-V Supervisor Binary Interface Specification [1]. One of its features is
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| to intercept run-time exceptions, e.g. for unaligned access or illegal
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| instructions, and to emulate the failing instructions.
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| 
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| The OpenSBI source can be downloaded via:
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| 
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| .. code-block:: bash
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| 
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|     git clone https://github.com/riscv/opensbi
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| 
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| As OpenSBI will be loaded at 0x80000000 we have to adjust the U-Boot text base.
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| Furthermore we have to enable building U-Boot for S-mode::
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| 
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|     CONFIG_SYS_TEXT_BASE=0x80020000
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|     CONFIG_RISCV_SMODE=y
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| 
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| Both settings are contained in sipeed_maix_smode_defconfig so we can build
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| U-Boot with:
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| 
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| .. code-block:: bash
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| 
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|     make sipeed_maix_smode_defconfig
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|     make
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| 
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| To build OpenSBI with U-Boot as a payload:
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| 
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| .. code-block:: bash
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| 
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|     cd opensbi
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|     make \
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|     PLATFORM=kendryte/k210 \
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|     FW_PAYLOAD=y \
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|     FW_PAYLOAD_OFFSET=0x20000 \
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|     FW_PAYLOAD_PATH=<path to U-Boot>/u-boot-dtb.bin
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| 
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| The value of FW_PAYLOAD_OFFSET must match CONFIG_SYS_TEXT_BASE - 0x80000000.
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| 
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| The file to flash is build/platform/kendryte/k210/firmware/fw_payload.bin.
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| 
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| Booting
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| ^^^^^^^
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| 
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| The default boot process is to load and boot the files ``/uImage`` and
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| ``/k210.dtb`` off of the first partition of the MMC. For Linux, this will result
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| in an output like
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| 
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| .. code-block:: none
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| 
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|     U-Boot 2020.10-00691-gd1d651d988-dirty (Oct 16 2020 - 17:05:24 -0400)
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| 
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|     DRAM:  8 MiB
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|     MMC:   spi@53000000:slot@0: 0
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|     Loading Environment from SPIFlash... SF: Detected w25q128fw with page size 256 Bytes, erase size 4 KiB, total 16 MiB
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|     OK
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|     In:    serial@38000000
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|     Out:   serial@38000000
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|     Err:   serial@38000000
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|     Hit any key to stop autoboot:  0
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|     1827380 bytes read in 1044 ms (1.7 MiB/s)
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|     13428 bytes read in 10 ms (1.3 MiB/s)
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|     ## Booting kernel from Legacy Image at 80060000 ...
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|        Image Name:   linux
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|        Image Type:   RISC-V Linux Kernel Image (uncompressed)
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|        Data Size:    1827316 Bytes = 1.7 MiB
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|        Load Address: 80000000
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|        Entry Point:  80000000
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|        Verifying Checksum ... OK
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|     ## Flattened Device Tree blob at 80400000
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|        Booting using the fdt blob at 0x80400000
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|        Loading Kernel Image
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|        Loading Device Tree to 00000000803f9000, end 00000000803ff473 ... OK
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| 
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|     Starting kernel ...
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| 
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|     [    0.000000] Linux version 5.9.0-00021-g6dcc2f0814c6-dirty (sean@godwin) (riscv64-linux-gnu-gcc (GCC) 10.2.0, GNU ld (GNU Binutils) 2.35) #34 SMP Fri Oct 16 14:40:57 EDT 2020
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|     [    0.000000] earlycon: sifive0 at MMIO 0x0000000038000000 (options '115200n8')
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|     [    0.000000] printk: bootconsole [sifive0] enabled
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|     [    0.000000] Zone ranges:
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|     [    0.000000]   DMA32    [mem 0x0000000080000000-0x00000000807fffff]
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|     [    0.000000]   Normal   empty
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|     [    0.000000] Movable zone start for each node
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|     [    0.000000] Early memory node ranges
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|     [    0.000000]   node   0: [mem 0x0000000080000000-0x00000000807fffff]
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|     [    0.000000] Initmem setup node 0 [mem 0x0000000080000000-0x00000000807fffff]
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|     [    0.000000] riscv: ISA extensions acdfgim
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|     [    0.000000] riscv: ELF capabilities acdfim
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|     [    0.000000] percpu: max_distance=0x18000 too large for vmalloc space 0x0
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|     [    0.000000] percpu: Embedded 12 pages/cpu s18848 r0 d30304 u49152
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|     [    0.000000] Built 1 zonelists, mobility grouping off.  Total pages: 2020
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|     [    0.000000] Kernel command line: earlycon console=ttySIF0
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|     [    0.000000] Dentry cache hash table entries: 1024 (order: 1, 8192 bytes, linear)
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|     [    0.000000] Inode-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
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|     [    0.000000] Sorting __ex_table...
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|     [    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
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|     [    0.000000] Memory: 6004K/8192K available (1139K kernel code, 126K rwdata, 198K rodata, 90K init, 81K bss, 2188K reserved, 0K cma-reserved)
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|     [    0.000000] rcu: Hierarchical RCU implementation.
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|     [    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
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|     [    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
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|     [    0.000000] riscv-intc: 64 local interrupts mapped
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|     [    0.000000] plic: interrupt-controller@C000000: mapped 65 interrupts with 2 handlers for 2 contexts.
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|     [    0.000000] random: get_random_bytes called from 0x00000000800019a8 with crng_init=0
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|     [    0.000000] k210-clk: clock-controller
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|     [    0.000000] k210-clk: clock-controller: fixed-rate 26 MHz osc base clock
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|     [    0.000000] clint: clint@2000000: timer running at 7800000 Hz
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|     [    0.000000] clocksource: clint_clocksource: mask: 0xffffffffffffffff max_cycles: 0x3990be68b, max_idle_ns: 881590404272 ns
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|     [    0.000014] sched_clock: 64 bits at 7MHz, resolution 128ns, wraps every 4398046511054ns
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|     [    0.008450] Console: colour dummy device 80x25
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|     [    0.012494] Calibrating delay loop (skipped), value calculated using timer frequency.. 15.60 BogoMIPS (lpj=31200)
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|     [    0.022693] pid_max: default: 4096 minimum: 301
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|     [    0.027352] Mount-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
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|     [    0.034428] Mountpoint-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
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|     [    0.045099] rcu: Hierarchical SRCU implementation.
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|     [    0.050048] smp: Bringing up secondary CPUs ...
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|     [    0.055417] smp: Brought up 1 node, 2 CPUs
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|     [    0.059602] devtmpfs: initialized
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|     [    0.082796] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
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|     [    0.091820] futex hash table entries: 16 (order: -2, 1024 bytes, linear)
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|     [    0.098507] pinctrl core: initialized pinctrl subsystem
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|     [    0.140938] clocksource: Switched to clocksource clint_clocksource
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|     [    0.247216] workingset: timestamp_bits=62 max_order=11 bucket_order=0
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|     [    0.277392] k210-fpioa 502b0000.pinmux: K210 FPIOA pin controller
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|     [    0.291724] k210-sysctl 50440000.syscon: K210 system controller
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|     [    0.305317] k210-rst 50440000.syscon:reset-controller: K210 reset controller
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|     [    0.313808] 38000000.serial: ttySIF0 at MMIO 0x38000000 (irq = 1, base_baud = 115200) is a SiFive UART v0
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|     [    0.322712] printk: console [ttySIF0] enabled
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|     [    0.322712] printk: console [ttySIF0] enabled
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|     [    0.331328] printk: bootconsole [sifive0] disabled
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|     [    0.331328] printk: bootconsole [sifive0] disabled
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|     [    0.353347] Freeing unused kernel memory: 88K
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|     [    0.357004] This architecture does not have kernel memory protection.
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|     [    0.363397] Run /init as init process
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| 
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| Loading, Booting, and Storing Images
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| ------------------------------------
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| 
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| .. _loading:
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| 
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| Loading Images
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| ^^^^^^^^^^^^^^
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| 
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| Serial
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| """"""
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| 
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| Use the ``loady`` command to load images over serial.
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| 
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| .. code-block:: none
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| 
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|     => loady $loadaddr 1500000
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|     ## Switch baudrate to 1500000 bps and press ENTER ...
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| 
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|     *** baud: 1500000
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| 
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|     *** baud: 1500000 ***
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|     ## Ready for binary (ymodem) download to 0x80000000 at 1500000 bps...
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|     C
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|     *** file: loader.bin
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|     $ sz -vv loader.bin
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|     Sending: loader.bin
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|     Bytes Sent:2478208   BPS:72937
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|     Sending:
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|     Ymodem sectors/kbytes sent:   0/ 0k
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|     Transfer complete
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| 
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|     *** exit status: 0 ***
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|     ## Total Size      = 0x0025d052 = 2478162 Bytes
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|     ## Switch baudrate to 115200 bps and press ESC ...
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| 
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|     *** baud: 115200
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| 
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|     *** baud: 115200 ***
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|     =>
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| 
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| This command does not set ``$filesize``, so it may need to be set manually.
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| 
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| SPI Flash
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| """""""""
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| 
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| To load an image off of SPI flash, first set up a partition as described in
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| :ref:`k210_partitions`. Then, use ``mtd`` to load that partition
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| 
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| .. code-block:: none
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| 
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|     => sf probe
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|     SF: Detected w25q128fw with page size 256 Bytes, erase size 4 KiB, total 16 MiB
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|     => mtd read linux $loadaddr
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|     Reading 2097152 byte(s) at offset 0x00000000
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| 
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| This command does not set ``$filesize``, so it may need to be set manually.
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| 
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| MMC
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| """
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| 
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| The MMC device number is 0. To list partitions on the device, use ``part``:
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| 
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| .. code-block:: none
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| 
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|     => part list mmc 0
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| 
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|     Partition Map for MMC device 0  --   Partition Type: EFI
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| 
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|     Part    Start LBA       End LBA          Name
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|             Attributes
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|             Type GUID
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|             Partition GUID
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|       1     0x00000800      0x039effde      "boot"
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|             attrs:  0x0000000000000000
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|             type:   c12a7328-f81f-11d2-ba4b-00a0c93ec93b
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|             guid:   96161f7d-7113-4cc7-9a24-08ab7fc5cb72
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| 
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| To list files, use ``ls``:
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| 
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| .. code-block:: none
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| 
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|     => ls mmc 0:1
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|     <DIR>       4096 .
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|     <DIR>       4096 ..
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|     <DIR>      16384 lost+found
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|                13428 k210.dtb
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|              1827380 uImage
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| 
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| To load a file, use ``load``:
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| 
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| .. code-block:: none
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| 
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|     => load mmc 0:1 $loadaddr uImage
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|     1827380 bytes read in 1049 ms (1.7 MiB/s)
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| 
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| Running Programs
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| ^^^^^^^^^^^^^^^^
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| 
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| Binaries
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| """"""""
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| 
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| To run a bare binary, use the ``go`` command:
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| 
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| .. code-block:: none
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| 
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|     => go 80000000
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|     ## Starting application at 0x80000000 ...
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|     Example expects ABI version 9
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|     Actual U-Boot ABI version 9
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|     Hello World
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|     argc = 1
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|     argv[0] = "80000000"
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|     argv[1] = "<NULL>"
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|     Hit any key to exit ...
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| 
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| Note that this will only start a program on one hart. As-of this writing it is
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| only possible to start a program on multiple harts using the ``bootm`` command.
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| 
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| Legacy Images
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| """""""""""""
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| 
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| To create a legacy image, use ``tools/mkimage``:
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| 
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| .. code-block:: none
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| 
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|     $ tools/mkimage -A riscv -O linux -T kernel -C none -a 0x80000000 -e 0x80000000 -n linux -d ../linux-git/arch/riscv/boot/Image uImage
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|     Image Name:   linux
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|     Created:      Fri Oct 16 17:36:32 2020
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|     Image Type:   RISC-V Linux Kernel Image (uncompressed)
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|     Data Size:    1827316 Bytes = 1784.49 KiB = 1.74 MiB
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|     Load Address: 80000000
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|     Entry Point:  80000000
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| 
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| The ``bootm`` command also requires an FDT, even if the image doesn't require
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| one. After loading the image to ``$loadaddr`` and the FDT to ``$fdt_addr_r``,
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| boot with:
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| 
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| .. code-block:: none
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| 
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|     => bootm $loadaddr - $fdt_addr_r
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|     ## Booting kernel from Legacy Image at 80060000 ...
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|        Image Name:   linux
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|        Image Type:   RISC-V Linux Kernel Image (uncompressed)
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|        Data Size:    1827316 Bytes = 1.7 MiB
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|        Load Address: 80000000
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|        Entry Point:  80000000
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|        Verifying Checksum ... OK
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|     ## Flattened Device Tree blob at 80400000
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|        Booting using the fdt blob at 0x80400000
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|        Loading Kernel Image
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|        Loading Device Tree to 00000000803f9000, end 00000000803ff473 ... OK
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| 
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|     Starting kernel ...
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| 
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| The FDT is verified after the kernel is relocated, so it must be loaded high
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| enough so that it won't be overwritten. The default values for ``$loadaddr``
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| and ``$fdt_addr_r`` should provide ample headroom for most use-cases.
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| 
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| Flashing Images
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| ^^^^^^^^^^^^^^^
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| 
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| SPI Flash
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| """""""""
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| 
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| To flash data to SPI flash, first load it using one of the methods in
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| :ref:`loading`. Addiotionally, create some partitions as described in
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| :ref:`partitions`. Then use the ``mtd`` command:
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| 
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| .. code-block:: none
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| 
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|     => sf probe
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|     SF: Detected w25q128fw with page size 256 Bytes, erase size 4 KiB, total 16 MiB
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|     => mtd write linux $loadaddr 0 $filesize
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|     Writing 2478162 byte(s) at offset 0x00000000
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| 
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| Note that in order to write a bootable image, a header and tailer must be added.
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| 
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| MMC
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| """
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| 
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| MMC writes are unsupported for now.
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| 
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| SPI Flash
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| ^^^^^^^^^
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| 
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| Sipeed MAIX boards typically provide around 16 MiB of SPI NOR flash. U-Boot is
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| stored in the first 1 MiB or so of this flash. U-Boot's environment is stored at
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| the end of flash.
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| 
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| .. _k210_partitions:
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| 
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| Partitions
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| """"""""""
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| 
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| There is no set data layout. The default partition layout only allocates
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| partitions for U-Boot and its default environment
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| 
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| .. code-block:: none
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| 
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|     => mtd list
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|     List of MTD devices:
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|     * nor0
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|       - type: NOR flash
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|       - block size: 0x1000 bytes
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|       - min I/O: 0x1 bytes
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|       - 0x000000000000-0x000001000000 : "nor0"
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|           - 0x000000000000-0x000000100000 : "u-boot"
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|           - 0x000000fff000-0x000001000000 : "env"
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| 
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| As an example, to allocate 2MiB for Linux and (almost) 13 MiB for other data,
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| set the ``mtdparts`` like:
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| 
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| .. code-block:: none
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| 
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|     => env set mtdparts nor0:1M(u-boot),2M(linux),0xcff000(data),0x1000@0xfff000(env)
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|     => mtd list
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|     List of MTD devices:
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|     * nor0
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|       - type: NOR flash
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|       - block size: 0x1000 bytes
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|       - min I/O: 0x1 bytes
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|       - 0x000000000000-0x000001000000 : "nor0"
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|           - 0x000000000000-0x000000100000 : "u-boot"
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|           - 0x000000100000-0x000000300000 : "linux"
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|           - 0x000000300000-0x000000fff000 : "data"
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|           - 0x000000fff000-0x000001000000 : "env"
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| 
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| To make these changes permanent, save the environment:
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| 
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| .. code-block:: none
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| 
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|     => env save
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|     Saving Environment to SPIFlash... Erasing SPI flash...Writing to SPI flash...done
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|     OK
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| 
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| U-Boot will always load the environment from the last 4 KiB of flash.
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| 
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| Pin Assignment
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| --------------
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| 
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| The K210 contains a Fully Programmable I/O Array (FPIOA), which can remap any of
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| its 256 input functions to any any of 48 output pins. The following table has
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| the default pin assignments for the BitM.
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| 
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| ===== ========== =======
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| Pin   Function   Comment
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| ===== ========== =======
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| IO_0  JTAG_TCLK
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| IO_1  JTAG_TDI
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| IO_2  JTAG_TMS
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| IO_3  JTAG_TDO
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| IO_4  UARTHS_RX
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| IO_5  UARTHS_TX
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| IO_6             Not set
 | |
| IO_7             Not set
 | |
| IO_8  GPIO_0
 | |
| IO_9  GPIO_1
 | |
| IO_10 GPIO_2
 | |
| IO_11 GPIO_3
 | |
| IO_12 GPIO_4     Green LED
 | |
| IO_13 GPIO_5     Red LED
 | |
| IO_14 GPIO_6     Blue LED
 | |
| IO_15 GPIO_7
 | |
| IO_16 GPIOHS_0   ISP
 | |
| IO_17 GPIOHS_1
 | |
| IO_18 I2S0_SCLK  MIC CLK
 | |
| IO_19 I2S0_WS    MIC WS
 | |
| IO_20 I2S0_IN_D0 MIC SD
 | |
| IO_21 GPIOHS_5
 | |
| IO_22 GPIOHS_6
 | |
| IO_23 GPIOHS_7
 | |
| IO_24 GPIOHS_8
 | |
| IO_25 GPIOHS_9
 | |
| IO_26 SPI1_D1    MMC MISO
 | |
| IO_27 SPI1_SCLK  MMC CLK
 | |
| IO_28 SPI1_D0    MMC MOSI
 | |
| IO_29 GPIOHS_13  MMC CS
 | |
| IO_30 GPIOHS_14
 | |
| IO_31 GPIOHS_15
 | |
| IO_32 GPIOHS_16
 | |
| IO_33 GPIOHS_17
 | |
| IO_34 GPIOHS_18
 | |
| IO_35 GPIOHS_19
 | |
| IO_36 GPIOHS_20  Panel CS
 | |
| IO_37 GPIOHS_21  Panel RST
 | |
| IO_38 GPIOHS_22  Panel DC
 | |
| IO_39 SPI0_SCK   Panel WR
 | |
| IO_40 SCCP_SDA
 | |
| IO_41 SCCP_SCLK
 | |
| IO_42 DVP_RST
 | |
| IO_43 DVP_VSYNC
 | |
| IO_44 DVP_PWDN
 | |
| IO_45 DVP_HSYNC
 | |
| IO_46 DVP_XCLK
 | |
| IO_47 DVP_PCLK
 | |
| ===== ========== =======
 | |
| 
 | |
| Over- and Under-clocking
 | |
| ------------------------
 | |
| 
 | |
| To change the clock speed of the K210, you will need to enable
 | |
| ``CONFIG_CLK_K210_SET_RATE`` and edit the board's device tree. To do this, add a
 | |
| section to ``arch/riscv/arch/riscv/dts/k210-maix-bit.dts`` like the following:
 | |
| 
 | |
| .. code-block:: none
 | |
| 
 | |
|     &sysclk {
 | |
| 	assigned-clocks = <&sysclk K210_CLK_PLL0>;
 | |
| 	assigned-clock-rates = <800000000>;
 | |
|     };
 | |
| 
 | |
| There are three PLLs on the K210: PLL0 is the parent of most of the components,
 | |
| including the CPU and RAM. PLL1 is the parent of the neural network coprocessor.
 | |
| PLL2 is the parent of the sound processing devices. Note that child clocks of
 | |
| PLL0 and PLL2 run at *half* the speed of the PLLs. For example, if PLL0 is
 | |
| running at 800 MHz, then the CPU will run at 400 MHz. This is the example given
 | |
| above. The CPU can be overclocked to around 600 MHz, and underclocked to 26 MHz.
 | |
| 
 | |
| It is possible to set PLL2's parent to PLL0. The plls are more accurate when
 | |
| converting between similar frequencies. This makes it easier to get an accurate
 | |
| frequency for I2S. As an example, consider sampling an I2S device at 44.1 kHz.
 | |
| On this device, the I2S serial clock runs at 64 times the sample rate.
 | |
| Therefore, we would like to run PLL2 at an even multiple of 2.8224 MHz. If
 | |
| PLL2's parent is IN0, we could use a frequency of 390 MHz (the same as the CPU's
 | |
| default speed).  Dividing by 138 yields a serial clock of about 2.8261 MHz. This
 | |
| results in a sample rate of 44.158 kHz---around 50 Hz or .1% too fast. If,
 | |
| instead, we set PLL2's parent to PLL1 running at 390 MHz, and request a rate of
 | |
| 2.8224 * 136 = 383.8464 MHz, the achieved rate is 383.90625 MHz. Dividing by 136
 | |
| yields a serial clock of about 2.8228 MHz. This results in a sample rate of
 | |
| 44.107 kHz---just 7 Hz or .02% too fast. This configuration is shown in the
 | |
| following example:
 | |
| 
 | |
| .. code-block:: none
 | |
| 
 | |
|     &sysclk {
 | |
| 	assigned-clocks = <&sysclk K210_CLK_PLL1>, <&sysclk K210_CLK_PLL2>;
 | |
| 	assigned-clock-parents = <0>, <&sysclk K210_CLK_PLL1>;
 | |
| 	assigned-clock-rates = <390000000>, <383846400>;
 | |
|     };
 | |
| 
 | |
| There are a couple of quirks to the PLLs. First, there are more frequency ratios
 | |
| just above and below 1.0, but there is a small gap around 1.0. To be explicit,
 | |
| if the input frequency is 100 MHz, it would be impossible to have an output of
 | |
| 99 or 101 MHz. In addition, there is a maximum frequency for the internal VCO,
 | |
| so higher input/output frequencies will be less accurate than lower ones.
 | |
| 
 | |
| Technical Details
 | |
| -----------------
 | |
| 
 | |
| Boot Sequence
 | |
| ^^^^^^^^^^^^^
 | |
| 
 | |
| 1. ``RESET`` pin is deasserted. The pin is connected to the ``RESET`` button. It
 | |
|    can also be set to low via either the ``DTR`` or the ``RTS`` line of the
 | |
|    serial interface (depending on the board).
 | |
| 2. Both harts begin executing at ``0x00001000``.
 | |
| 3. Both harts jump to firmware at ``0x88000000``.
 | |
| 4. One hart is chosen as a boot hart.
 | |
| 5. Firmware reads the value of pin ``IO_16`` (ISP). This pin is connected to the
 | |
|    ``BOOT`` button. The pin can equally be set to low via either the ``DTR`` or
 | |
|    ``RTS`` line of the serial interface (depending on the board).
 | |
| 
 | |
|    * If the pin is low, enter ISP mode. This mode allows loading data to ram,
 | |
|      writing it to flash, and booting from specific addresses.
 | |
|    * If the pin is high, continue boot.
 | |
| 6. Firmware reads the next stage from flash (SPI3) to address ``0x80000000``.
 | |
| 
 | |
|    * If byte 0 is 1, the next stage is decrypted using the built-in AES
 | |
|      accelerator and the one-time programmable, 128-bit AES key.
 | |
|    * Bytes 1 to 4 hold the length of the next stage.
 | |
|    * The SHA-256 sum of the next stage is automatically calculated, and verified
 | |
|      against the 32 bytes following the next stage.
 | |
| 7. The boot hart sends an IPI to the other hart telling it to jump to the next
 | |
|    stage.
 | |
| 8. The boot hart jumps to ``0x80000000``.
 | |
| 
 | |
| Debug UART
 | |
| ^^^^^^^^^^
 | |
| 
 | |
| The Debug UART is provided with the following settings::
 | |
| 
 | |
|     CONFIG_DEBUG_UART=y
 | |
|     CONFIG_DEBUG_UART_SIFIVE=y
 | |
|     CONFIG_DEBUG_UART_BASE=0x38000000
 | |
|     CONFIG_DEBUG_UART_CLOCK=390000000
 | |
| 
 | |
| Resetting the board
 | |
| ^^^^^^^^^^^^^^^^^^^
 | |
| 
 | |
| The MAIX boards can be reset using the DTR and RTS lines of the serial console.
 | |
| How the lines are used depends on the specific board. See the code of kflash.py
 | |
| for details.
 | |
| 
 | |
| This is the reset sequence for the MAXDUINO and MAIX BiT with Mic:
 | |
| 
 | |
| .. code-block:: python
 | |
| 
 | |
|    def reset(self):
 | |
|         self.device.setDTR(False)
 | |
|         self.device.setRTS(False)
 | |
|         time.sleep(0.1)
 | |
|         self.device.setDTR(True)
 | |
|         time.sleep(0.1)
 | |
|         self.device.setDTR(False)
 | |
|         time.sleep(0.1)
 | |
| 
 | |
| and this for the MAIX Bit:
 | |
| 
 | |
| .. code-block:: python
 | |
| 
 | |
|    def reset(self):
 | |
|         self.device.setDTR(False)
 | |
|         self.device.setRTS(False)
 | |
|         time.sleep(0.1)
 | |
|         self.device.setRTS(True)
 | |
|         time.sleep(0.1)
 | |
|         self.device.setRTS(False)
 | |
|         time.sleep(0.1)
 | |
| 
 | |
| Memory Map
 | |
| ^^^^^^^^^^
 | |
| 
 | |
| ========== ========= ===========
 | |
| Address    Size      Description
 | |
| ========== ========= ===========
 | |
| 0x00000000 0x1000    debug
 | |
| 0x00001000 0x1000    rom
 | |
| 0x02000000 0xC000    clint
 | |
| 0x0C000000 0x4000000 plic
 | |
| 0x38000000 0x1000    uarths
 | |
| 0x38001000 0x1000    gpiohs
 | |
| 0x40000000 0x400000  sram0 (non-cached)
 | |
| 0x40400000 0x200000  sram1 (non-cached)
 | |
| 0x40600000 0x200000  airam (non-cached)
 | |
| 0x40800000 0xC00000  kpu
 | |
| 0x42000000 0x400000  fft
 | |
| 0x50000000 0x1000    dmac
 | |
| 0x50200000 0x200000  apb0
 | |
| 0x50200000 0x80      gpio
 | |
| 0x50210000 0x100     uart0
 | |
| 0x50220000 0x100     uart1
 | |
| 0x50230000 0x100     uart2
 | |
| 0x50240000 0x100     spi slave
 | |
| 0x50250000 0x200     i2s0
 | |
| 0x50250200 0x200     apu
 | |
| 0x50260000 0x200     i2s1
 | |
| 0x50270000 0x200     i2s2
 | |
| 0x50280000 0x100     i2c0
 | |
| 0x50290000 0x100     i2c1
 | |
| 0x502A0000 0x100     i2c2
 | |
| 0x502B0000 0x100     fpioa
 | |
| 0x502C0000 0x100     sha256
 | |
| 0x502D0000 0x100     timer0
 | |
| 0x502E0000 0x100     timer1
 | |
| 0x502F0000 0x100     timer2
 | |
| 0x50400000 0x200000  apb1
 | |
| 0x50400000 0x100     wdt0
 | |
| 0x50410000 0x100     wdt1
 | |
| 0x50420000 0x100     otp control
 | |
| 0x50430000 0x100     dvp
 | |
| 0x50440000 0x100     sysctl
 | |
| 0x50450000 0x100     aes
 | |
| 0x50460000 0x100     rtc
 | |
| 0x52000000 0x4000000 apb2
 | |
| 0x52000000 0x100     spi0
 | |
| 0x53000000 0x100     spi1
 | |
| 0x54000000 0x200     spi3
 | |
| 0x80000000 0x400000  sram0 (cached)
 | |
| 0x80400000 0x200000  sram1 (cached)
 | |
| 0x80600000 0x200000  airam (cached)
 | |
| 0x88000000 0x20000   otp
 | |
| 0x88000000 0xC200    firmware
 | |
| 0x8801C000 0x1000    riscv priv spec 1.9 config
 | |
| 0x8801D000 0x2000    flattened device tree (contains only addresses and
 | |
|                      interrupts)
 | |
| 0x8801F000 0x1000    credits
 | |
| ========== ========= ===========
 | |
| 
 | |
| Links
 | |
| -----
 | |
| 
 | |
| [1] https://github.com/riscv/riscv-sbi-doc
 | |
|     RISC-V Supervisor Binary Interface Specification
 |