ARM: meson: Add boot device discovery

The Amlogic Meson SoCs ROM supports a boot over USB with a custom protocol.

When no other boot medium are available (or by forcing the USB mode), the
ROM sets the primary USB port as device mode and waits for a Host to
enumerate.

When enumerated, a custom protocol described at [1] permits writing to
memory and execute some specific FIP init code to run the loaded
Arm Trusted Firmware BL2 and BL3 stages before running the BL33 stage.

In this mode, we can load different binaries that can be used by U-boot
like a script image file.

This adds support for a custom USB boot stage only available when the
boot mode is USB and the script file at a pre-defined address is valid.
This support was heavily copied from the Sunxi Allwinner FEL U-Boot support.

The tool pyamlboot described at [2], permits using this boot mode on boards
exposing the first USB port, either as OTG or Host port.

[1] https://github.com/superna9999/pyamlboot/blob/master/PROTOCOL.md
[2] https://github.com/superna9999/pyamlboot/blob/master/README.md

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

arch/arm/include/asm/arch-meson/axg.h

@@ -20,6 +20,7 @@
 #define AXG_AO_SEC_GP_CFG4	AXG_AO_ADDR(0x94)
 #define AXG_AO_SEC_GP_CFG5	AXG_AO_ADDR(0x95)
 
+#define AXG_AO_BOOT_DEVICE	0xF
 #define AXG_AO_MEM_SIZE_MASK	0xFFFF0000
 #define AXG_AO_MEM_SIZE_SHIFT	16
 #define AXG_AO_BL31_RSVMEM_SIZE_MASK	0xFFFF0000

arch/arm/include/asm/arch-meson/boot.h

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2016 BayLibre, SAS
+ * Author: Neil Armstrong <narmstrong@baylibre.com>
+ */
+
+#ifndef __MESON_BOOT_H__
+#define __MESON_BOOT_H__
+
+/* Boot device */
+#define BOOT_DEVICE_RESERVED    0
+#define BOOT_DEVICE_EMMC        1
+#define BOOT_DEVICE_NAND        2
+#define BOOT_DEVICE_SPI         3
+#define BOOT_DEVICE_SD          4
+#define BOOT_DEVICE_USB         5
+
+int meson_get_boot_device(void);
+
+#endif /* __MESON_BOOT_H__ */

arch/arm/include/asm/arch-meson/gx.h

@@ -21,6 +21,7 @@
 #define GX_AO_SEC_GP_CFG4	GX_AO_ADDR(0x94)
 #define GX_AO_SEC_GP_CFG5	GX_AO_ADDR(0x95)
 
+#define GX_AO_BOOT_DEVICE	0xF
 #define GX_AO_MEM_SIZE_MASK	0xFFFF0000
 #define GX_AO_MEM_SIZE_SHIFT	16
 #define GX_AO_BL31_RSVMEM_SIZE_MASK	0xFFFF0000

arch/arm/mach-meson/Kconfig

@@ -8,6 +8,7 @@ config MESON64_COMMON
 	select DM_SERIAL
 	select SYSCON
 	select REGMAP
+	select BOARD_LATE_INIT
 	imply CMD_DM
 
 config MESON_GX

arch/arm/mach-meson/board-axg.c

@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <asm/arch/boot.h>
 #include <asm/arch/eth.h>
 #include <asm/arch/axg.h>
 #include <asm/arch/mem.h>
@@ -15,6 +16,11 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+int meson_get_boot_device(void)
+{
+	return readl(AXG_AO_SEC_GP_CFG0) & AXG_AO_BOOT_DEVICE;
+}
+
 /* Configure the reserved memory zones exported by the secure registers
  * into EFI and DTB reserved memory entries.
  */

arch/arm/mach-meson/board-common.c

@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <asm/arch/boot.h>
 #include <linux/libfdt.h>
 #include <linux/err.h>
 #include <asm/arch/mem.h>
@@ -66,6 +67,50 @@ void meson_board_add_reserved_memory(void *fdt, u64 start, u64 size)
 	}
 }
 
+static void meson_set_boot_source(void)
+{
+	const char *source;
+
+	switch (meson_get_boot_device()) {
+	case BOOT_DEVICE_EMMC:
+		source = "emmc";
+		break;
+
+	case BOOT_DEVICE_NAND:
+		source = "nand";
+		break;
+
+	case BOOT_DEVICE_SPI:
+		source = "spi";
+		break;
+
+	case BOOT_DEVICE_SD:
+		source = "sd";
+		break;
+
+	case BOOT_DEVICE_USB:
+		source = "usb";
+		break;
+
+	default:
+		source = "unknown";
+	}
+
+	env_set("boot_source", source);
+}
+
+__weak int meson_board_late_init(void)
+{
+	return 0;
+}
+
+int board_late_init(void)
+{
+	meson_set_boot_source();
+
+	return meson_board_late_init();
+}
+
 void reset_cpu(ulong addr)
 {
 	psci_system_reset();

arch/arm/mach-meson/board-gx.c

@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <asm/arch/boot.h>
 #include <asm/arch/eth.h>
 #include <asm/arch/gx.h>
 #include <asm/arch/mem.h>
@@ -15,6 +16,11 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+int meson_get_boot_device(void)
+{
+	return readl(GX_AO_SEC_GP_CFG0) & GX_AO_BOOT_DEVICE;
+}
+
 /* Configure the reserved memory zones exported by the secure registers
  * into EFI and DTB reserved memory entries.
  */

include/configs/meson64.h

@@ -28,6 +28,18 @@
 #define CONFIG_SYS_LOAD_ADDR		CONFIG_SYS_TEXT_BASE
 #define CONFIG_SYS_BOOTM_LEN		(64 << 20) /* 64 MiB */
 
+/* ROM USB boot support, auto-execute boot.scr at scriptaddr */
+#define BOOTENV_DEV_ROMUSB(devtypeu, devtypel, instance) \
+	"bootcmd_romusb=" \
+		"if test \"${boot_source}\" = \"usb\" && " \
+				"test -n \"${scriptaddr}\"; then " \
+			"echo '(ROM USB boot)'; " \
+			"source ${scriptaddr}; " \
+		"fi\0"
+
+#define BOOTENV_DEV_NAME_ROMUSB(devtypeu, devtypel, instance)	\
+		"romusb "
+
 #ifdef CONFIG_CMD_USB
 #define BOOT_TARGET_DEVICES_USB(func) func(USB, usb, 0)
 #else
@@ -36,6 +48,7 @@
 
 #ifndef BOOT_TARGET_DEVICES
 #define BOOT_TARGET_DEVICES(func) \
+	func(ROMUSB, romusb, na)  \
 	func(MMC, mmc, 0) \
 	func(MMC, mmc, 1) \
 	func(MMC, mmc, 2) \