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>

4 files changed, 58 insertions, 0 deletions

diff --git a/arch/arm/mach-meson/Kconfig b/arch/arm/mach-meson/Kconfig
index deddcc5ab0..11077bc6cc 100644
--- a/arch/arm/mach-meson/Kconfig
+++ b/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
diff --git a/arch/arm/mach-meson/board-axg.c b/arch/arm/mach-meson/board-axg.c
index 014b25d61a..173905e762 100644
--- a/arch/arm/mach-meson/board-axg.c
+++ b/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.
  */
diff --git a/arch/arm/mach-meson/board-common.c b/arch/arm/mach-meson/board-common.c
index 8c4f3074fb..8c41301674 100644
--- a/arch/arm/mach-meson/board-common.c
+++ b/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();
diff --git a/arch/arm/mach-meson/board-gx.c b/arch/arm/mach-meson/board-gx.c
index f1397f87c5..e41552db52 100644
--- a/arch/arm/mach-meson/board-gx.c
+++ b/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.
  */