arm: Add support for ST-Ericsson U8500 SoC

The NovaThor U8500 SoC was released by ST-Ericsson in 2011.
It was used for some development boards like the CALAO Systems
Snowball SBC, but mass production was primarily for Android
smartphones like the Samsung Galaxy S III mini.

Previous support for U8500 was removed in
commit 68282f55b8 ("arm: Remove unused ST-Ericsson u8500 arch")
since none of the boards were converted to generic boards
before the deadline.

The new code does not have much in common with the previous code.
I have completely rewritten everything, embracing the Driver Model
and device trees wherever possible.

The U8500 support is a bit more minimal for now - my primary
use case is to use U-Boot as alternative bootloader for some of the
U8500 Samsung smartphones. At the moment U-Boot is chain-loaded from
the original Samsung bootloader. A side effect of this is that we
can (temporarily) get away without implementing some functionality
- e.g. all clocks are already enabled by the original bootloader.

More functionality will be added in future patches.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: John Rigby <john.rigby@linaro.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/Kconfig

@@ -1009,6 +1009,24 @@ config ARCH_SUNXI
 	imply SPL_SERIAL_SUPPORT
 	imply USB_GADGET
 
+config ARCH_U8500
+	bool "ST-Ericsson U8500 Series"
+	select CPU_V7A
+	select DM
+	select DM_GPIO
+	select DM_MMC if MMC
+	select DM_SERIAL
+	select DM_USB if USB
+	select OF_CONTROL
+	select SYSRESET
+	select TIMER
+	imply ARM_PL180_MMCI
+	imply DM_RTC
+	imply NOMADIK_MTU_TIMER
+	imply PL01X_SERIAL
+	imply RTC_PL031
+	imply SYSRESET_SYSCON
+
 config ARCH_VERSAL
 	bool "Support Xilinx Versal Platform"
 	select ARM64
@@ -1779,6 +1797,8 @@ source "arch/arm/mach-sunxi/Kconfig"
 
 source "arch/arm/mach-tegra/Kconfig"
 
+source "arch/arm/mach-u8500/Kconfig"
+
 source "arch/arm/mach-uniphier/Kconfig"
 
 source "arch/arm/cpu/armv7/vf610/Kconfig"

arch/arm/Makefile

@@ -79,6 +79,7 @@ machine-$(CONFIG_ARCH_ROCKCHIP)		+= rockchip
 machine-$(CONFIG_STM32)			+= stm32
 machine-$(CONFIG_ARCH_STM32MP)		+= stm32mp
 machine-$(CONFIG_TEGRA)			+= tegra
+machine-$(CONFIG_ARCH_U8500)		+= u8500
 machine-$(CONFIG_ARCH_UNIPHIER)		+= uniphier
 machine-$(CONFIG_ARCH_ZYNQ)		+= zynq
 machine-$(CONFIG_ARCH_ZYNQMP)		+= zynqmp

arch/arm/dts/ste-dbx5x0-u-boot.dtsi

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "skeleton.dtsi"
+#include "ste-dbx5x0.dtsi"
+
+/ {
+	soc {
+		/* FIXME: Remove this when clk driver is implemented */
+		mtu@a03c6000 {
+			clock-frequency = <133000000>;
+		};
+		uart@80120000 {
+			clock = <38400000>;
+		};
+		uart@80121000 {
+			clock = <38400000>;
+		};
+		uart@80007000 {
+			clock = <38400000>;
+		};
+	};
+
+	reboot {
+		compatible = "syscon-reboot";
+		regmap = <&prcmu>;
+		offset = <0x228>; /* PRCM_APE_SOFTRST */
+		mask = <0x1>;
+	};
+};

arch/arm/include/asm/gpio.h

@@ -3,7 +3,7 @@
 	!defined(CONFIG_ARCH_BCM63158) && !defined(CONFIG_ARCH_ROCKCHIP) && \
 	!defined(CONFIG_ARCH_LX2160A) && !defined(CONFIG_ARCH_LS1028A) && \
 	!defined(CONFIG_ARCH_LS2080A) && !defined(CONFIG_ARCH_LS1088A) && \
-	!defined(CONFIG_ARCH_ASPEED)
+	!defined(CONFIG_ARCH_ASPEED) && !defined(CONFIG_ARCH_U8500)
 #include <asm/arch/gpio.h>
 #endif
 #include <asm-generic/gpio.h>

arch/arm/mach-u8500/Kconfig

@@ -0,0 +1,6 @@
+if ARCH_U8500
+
+config SYS_SOC
+	default "u8500"
+
+endif

arch/arm/mach-u8500/Makefile

@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+obj-y	+= cache.o
+obj-$(CONFIG_DISPLAY_CPUINFO)	+= cpuinfo.o

arch/arm/mach-u8500/cache.c

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2019 Stephan Gerhold <stephan@gerhold.net>
+ */
+
+#include <common.h>
+#include <cpu_func.h>
+#include <asm/armv7.h>
+#include <asm/pl310.h>
+
+#define PL310_WAY_MASK	0xff
+
+#if !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)
+void enable_caches(void)
+{
+	/* Enable D-cache. I-cache is already enabled in start.S */
+	dcache_enable();
+}
+#endif
+
+#ifdef CONFIG_SYS_L2_PL310
+void v7_outer_cache_disable(void)
+{
+	struct pl310_regs *const pl310 = (struct pl310_regs *)CONFIG_SYS_PL310_BASE;
+
+	/*
+	 * Linux expects the L2 cache to be turned off by the bootloader.
+	 * Otherwise, it fails very early (shortly after decompressing the kernel).
+	 *
+	 * On U8500, the L2 cache can be only turned on/off from the secure world.
+	 * Instead, prevent usage of the L2 cache by locking all ways.
+	 * The kernel needs to unlock them to make the L2 cache work again.
+	 */
+	writel(PL310_WAY_MASK, &pl310->pl310_lockdown_dbase);
+	writel(PL310_WAY_MASK, &pl310->pl310_lockdown_ibase);
+}
+#endif

arch/arm/mach-u8500/cpuinfo.c

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2019 Stephan Gerhold <stephan@gerhold.net>
+ */
+
+#include <common.h>
+#include <asm/io.h>
+
+#define U8500_BOOTROM_BASE	0x90000000
+#define U8500_ASIC_ID_LOC_V2	(U8500_BOOTROM_BASE + 0x1DBF4)
+
+int print_cpuinfo(void)
+{
+	/* Convert ASIC ID to display string, e.g. 0x8520A0 => DB8520 V1.0 */
+	u32 asicid = readl(U8500_ASIC_ID_LOC_V2);
+	u32 cpu = (asicid >> 8) & 0xffff;
+	u32 rev = asicid & 0xff;
+
+	/* 0xA0 => 0x10 (V1.0) */
+	if (rev >= 0xa0)
+		rev -= 0x90;
+
+	printf("CPU: ST-Ericsson DB%x V%d.%d\n", cpu, rev >> 4, rev & 0xf);
+	return 0;
+}