riscv: add SPL support

U-Boot SPL on the generic RISC-V CPU supports two boot flows, directly
jumping to the image and via OpenSBI firmware. In the first case, both
U-Boot SPL and proper must be compiled to run in the same privilege
mode. Using OpenSBI firmware, U-Boot SPL must be compiled for machine
mode and U-Boot proper for supervisor mode.

To be able to use SPL, boards have to provide a supported SPL boot
device.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>

arch/Kconfig

@@ -76,6 +76,12 @@ config RISCV
 	imply MTD
 	imply TIMER
 	imply CMD_DM
+	imply SPL_DM
+	imply SPL_OF_CONTROL
+	imply SPL_LIBCOMMON_SUPPORT
+	imply SPL_LIBGENERIC_SUPPORT
+	imply SPL_SERIAL_SUPPORT
+	imply SPL_TIMER
 
 config SANDBOX
 	bool "Sandbox"

arch/riscv/Kconfig

@@ -226,4 +226,7 @@ config STACK_SIZE_SHIFT
 	int
 	default 13
 
+config SPL_LDSCRIPT
+	default "arch/riscv/cpu/u-boot-spl.lds"
+
 endmenu

arch/riscv/cpu/generic/Kconfig

@@ -10,3 +10,6 @@ config GENERIC_RISCV
 	imply RISCV_TIMER
 	imply SIFIVE_CLINT if (RISCV_MMODE || SPL_RISCV_MMODE)
 	imply CMD_CPU
+	imply SPL_CPU_SUPPORT
+	imply SPL_OPENSBI
+	imply SPL_LOAD_FIT

arch/riscv/cpu/start.S

@@ -75,7 +75,11 @@ _start:
  */
 call_board_init_f:
 	li	t0, -16
+#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
+	li	t1, CONFIG_SPL_STACK
+#else
 	li	t1, CONFIG_SYS_INIT_SP_ADDR
+#endif
 	and	sp, t1, t0		/* force 16 byte alignment */
 
 call_board_init_f_0:
@@ -159,7 +163,24 @@ wait_for_gd_init:
 
 	mv	a0, zero		/* a0 <-- boot_flags = 0 */
 	la	t5, board_init_f
-	jr	t5			/* jump to board_init_f() */
+	jalr	t5			/* jump to board_init_f() */
+
+#ifdef CONFIG_SPL_BUILD
+spl_clear_bss:
+	la	t0, __bss_start
+	la	t1, __bss_end
+	beq	t0, t1, spl_call_board_init_r
+
+spl_clear_bss_loop:
+	SREG	zero, 0(t0)
+	addi	t0, t0, REGBYTES
+	bne	t0, t1, spl_clear_bss_loop
+
+spl_call_board_init_r:
+	mv	a0, zero
+	mv	a1, zero
+	jal	board_init_r
+#endif
 
 /*
  * void relocate_code (addr_sp, gd, addr_moni)

arch/riscv/cpu/u-boot-spl.lds

@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Based on arch/riscv/cpu/u-boot.lds, which is
+ * Copyright (C) 2017 Andes Technology Corporation
+ * Rick Chen, Andes Technology Corporation <rick@andestech.com>
+ *
+ * and arch/mips/cpu/u-boot-spl.lds.
+ */
+MEMORY { .spl_mem : ORIGIN = IMAGE_TEXT_BASE, LENGTH = IMAGE_MAX_SIZE }
+MEMORY { .bss_mem : ORIGIN = CONFIG_SPL_BSS_START_ADDR, \
+		    LENGTH = CONFIG_SPL_BSS_MAX_SIZE }
+
+OUTPUT_ARCH("riscv")
+ENTRY(_start)
+
+SECTIONS
+{
+	. = ALIGN(4);
+	.text : {
+		arch/riscv/cpu/start.o	(.text)
+		*(.text*)
+	} > .spl_mem
+
+	. = ALIGN(4);
+	.rodata : {
+		*(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*)))
+	} > .spl_mem
+
+	. = ALIGN(4);
+	.data : {
+		*(.data*)
+	} > .spl_mem
+	. = ALIGN(4);
+
+	.got : {
+		__got_start = .;
+		*(.got.plt) *(.got)
+		__got_end = .;
+	} > .spl_mem
+
+	. = ALIGN(4);
+
+	.u_boot_list : {
+		KEEP(*(SORT(.u_boot_list*)));
+	} > .spl_mem
+
+	. = ALIGN(4);
+
+	.binman_sym_table : {
+		__binman_sym_start = .;
+		KEEP(*(SORT(.binman_sym*)));
+		__binman_sym_end = .;
+	} > .spl_mem
+
+	. = ALIGN(4);
+
+	/DISCARD/ : { *(.rela.plt*) }
+	.rela.dyn : {
+		__rel_dyn_start = .;
+		*(.rela*)
+		__rel_dyn_end = .;
+	} > .spl_mem
+
+	. = ALIGN(4);
+
+	.dynsym : {
+		__dyn_sym_start = .;
+		*(.dynsym)
+		__dyn_sym_end = .;
+	} > .spl_mem
+
+	. = ALIGN(4);
+
+	_end = .;
+
+	.bss : {
+		__bss_start = .;
+		*(.bss*)
+		. = ALIGN(4);
+		__bss_end = .;
+	} > .bss_mem
+}

arch/riscv/include/asm/spl.h

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Based on arch/mips/include/asm/spl.h.
+ *
+ * (C) Copyright 2012
+ * Texas Instruments, <www.ti.com>
+ */
+#ifndef _ASM_RISCV_SPL_H_
+#define _ASM_RISCV_SPL_H_
+
+enum {
+	BOOT_DEVICE_RAM,
+	BOOT_DEVICE_MMC1,
+	BOOT_DEVICE_MMC2,
+	BOOT_DEVICE_MMC2_2,
+	BOOT_DEVICE_NAND,
+	BOOT_DEVICE_ONENAND,
+	BOOT_DEVICE_NOR,
+	BOOT_DEVICE_UART,
+	BOOT_DEVICE_SPI,
+	BOOT_DEVICE_USB,
+	BOOT_DEVICE_SATA,
+	BOOT_DEVICE_I2C,
+	BOOT_DEVICE_BOARD,
+	BOOT_DEVICE_DFU,
+	BOOT_DEVICE_XIP,
+	BOOT_DEVICE_BOOTROM,
+	BOOT_DEVICE_NONE
+};
+
+#endif

arch/riscv/lib/Makefile

@@ -22,6 +22,7 @@ obj-y	+= interrupts.o
 obj-y	+= reset.o
 obj-y   += setjmp.o
 obj-$(CONFIG_SMP) += smp.o
+obj-$(CONFIG_SPL_BUILD)	+= spl.o
 
 # For building EFI apps
 CFLAGS_$(EFI_CRT0) := $(CFLAGS_EFI)

arch/riscv/lib/spl.c

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Fraunhofer AISEC,
+ * Lukas Auer <lukas.auer@aisec.fraunhofer.de>
+ */
+#include <common.h>
+#include <spl.h>
+#include <asm/smp.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+__weak void board_init_f(ulong dummy)
+{
+	int ret;
+
+	ret = spl_early_init();
+	if (ret)
+		panic("spl_early_init() failed: %d\n", ret);
+
+	arch_cpu_init_dm();
+
+	preloader_console_init();
+}
+
+void __noreturn jump_to_image_no_args(struct spl_image_info *spl_image)
+{
+	typedef void __noreturn (*image_entry_riscv_t)(ulong hart, void *dtb);
+	void *fdt_blob;
+	int ret;
+
+#if CONFIG_IS_ENABLED(LOAD_FIT) || CONFIG_IS_ENABLED(LOAD_FIT_FULL)
+	fdt_blob = spl_image->fdt_addr;
+#else
+	fdt_blob = (void *)gd->fdt_blob;
+#endif
+
+	image_entry_riscv_t image_entry =
+		(image_entry_riscv_t)spl_image->entry_point;
+	invalidate_icache_all();
+
+	debug("image entry point: 0x%lX\n", spl_image->entry_point);
+#ifdef CONFIG_SMP
+	ret = smp_call_function(spl_image->entry_point, (ulong)fdt_blob, 0);
+	if (ret)
+		hang();
+#endif
+	image_entry(gd->arch.boot_hart, fdt_blob);
+}