ARM: sama5d2: Implement boot device autodetection
Implement support for saving ARM register R4 early during boot using
save_boot_params . Implement support for decoding the stored register
R4 value in spl_boot_device() to obtain boot device from which the
SoC booted. This way, the SPL will always load U-Boot from the same
device from which the SPL itself booted instead of using hard-coded
boot device.
This functionality is useful for example when booting sama5d2-xplained
from SD card, where by default the SPL would try loading the U-Boot
from eMMC and fail. This is because eMMC is on SDHCI0 (BOOT_DEVICE_MMC1),
while SD slot is on SDHCI1 (BOOT_DEVICE_MMC2) and the SPL was hard-wired
to always boot from BOOT_DEVICE_MMC1.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andreas Bießmann <andreas.devel@googlemail.com>
Cc: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Andreas Bießmann <andreas@biessmann.org>
diff --git a/arch/arm/mach-at91/bootparams_atmel.S b/arch/arm/mach-at91/bootparams_atmel.S
new file mode 100644
index 0000000..568094b
--- /dev/null
+++ b/arch/arm/mach-at91/bootparams_atmel.S
@@ -0,0 +1,18 @@
+/*
+ * Atmel SAMA5Dx boot parameter handling
+ *
+ * Copyright (c) 2016 Marek Vasut <marex@denx.de>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <asm-offsets.h>
+#include <config.h>
+#include <asm/system.h>
+#include <linux/linkage.h>
+
+ENTRY(save_boot_params)
+ ldr r0, =bootrom_stash
+ str r4, [r0, #0]
+ b save_boot_params_ret
+ENDPROC(save_boot_params)