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: NMarek Vasut <marex@denx.de>
Cc: Andreas Bießmann <andreas.devel@googlemail.com>
Cc: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: NAndreas Bießmann <andreas@biessmann.org>

arch/arm/mach-at91/Makefile

@@ -9,7 +9,7 @@ obj-$(CONFIG_AT91SAM9G20) += sdram.o spl_at91.o
 obj-$(CONFIG_AT91SAM9M10G45) += mpddrc.o spl_at91.o
 obj-$(CONFIG_AT91SAM9N12) += mpddrc.o spl_at91.o
 obj-$(CONFIG_AT91SAM9X5) += mpddrc.o spl_at91.o
-obj-$(CONFIG_SAMA5D2) += mpddrc.o spl_atmel.o matrix.o atmel_sfr.o
+obj-$(CONFIG_SAMA5D2) += bootparams_atmel.o mpddrc.o spl_atmel.o matrix.o atmel_sfr.o
 obj-$(CONFIG_SAMA5D3) += mpddrc.o spl_atmel.o
 obj-$(CONFIG_SAMA5D4) += mpddrc.o spl_atmel.o matrix.o atmel_sfr.o
 obj-y += spl.o

arch/arm/mach-at91/bootparams_atmel.S

+/*
+ * 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)

arch/arm/mach-at91/include/mach/sama5d2.h

@@ -230,6 +230,18 @@
 /* No PMECC Galois table in ROM */
 #define NO_GALOIS_TABLE_IN_ROM
 
+/* Boot modes stored by BootROM in r4 */
+#define ATMEL_SAMA5D2_BOOT_FROM_OFF	0
+#define ATMEL_SAMA5D2_BOOT_FROM_MASK	0xf
+#define ATMEL_SAMA5D2_BOOT_FROM_SPI	(0 << 0)
+#define ATMEL_SAMA5D2_BOOT_FROM_MCI	(1 << 0)
+#define ATMEL_SAMA5D2_BOOT_FROM_SMC	(2 << 0)
+#define ATMEL_SAMA5D2_BOOT_FROM_TWI	(3 << 0)
+#define ATMEL_SAMA5D2_BOOT_FROM_QSPI	(4 << 0)
+
+#define ATMEL_SAMA5D2_BOOT_DEV_ID_OFF	4
+#define ATMEL_SAMA5D2_BOOT_DEV_ID_MASK	0xf
+
 #ifndef __ASSEMBLY__
 unsigned int get_chip_id(void);
 unsigned int get_extension_chip_id(void);

arch/arm/mach-at91/spl.c

@@ -23,6 +23,40 @@ void at91_disable_wdt(void)
 }
 #endif
 
+#if defined(CONFIG_SAMA5D2)
+struct {
+	u32	r4;
+} bootrom_stash __attribute__((section(".data")));
+
+u32 spl_boot_device(void)
+{
+	u32 dev = (bootrom_stash.r4 >> ATMEL_SAMA5D2_BOOT_FROM_OFF) &
+		  ATMEL_SAMA5D2_BOOT_FROM_MASK;
+	u32 off = (bootrom_stash.r4 >> ATMEL_SAMA5D2_BOOT_DEV_ID_OFF) &
+		  ATMEL_SAMA5D2_BOOT_DEV_ID_MASK;
+
+#if defined(CONFIG_SYS_USE_MMC)
+	if (dev == ATMEL_SAMA5D2_BOOT_FROM_MCI) {
+		if (off == 0)
+			return BOOT_DEVICE_MMC1;
+		if (off == 1)
+			return BOOT_DEVICE_MMC2;
+		printf("ERROR: MMC controller %i not present!\n", dev);
+		hang();
+	}
+#endif
+
+#if defined(CONFIG_SYS_USE_SERIALFLASH) || defined(CONFIG_SYS_USE_SPIFLASH)
+	if (dev == ATMEL_SAMA5D2_BOOT_FROM_SPI)
+		return BOOT_DEVICE_SPI;
+#endif
+
+	printf("ERROR: SMC/TWI/QSPI boot device not supported!\n"
+	       "       Boot device %i, controller number %i\n", dev, off);
+
+	return BOOT_DEVICE_NONE;
+}
+#else
 u32 spl_boot_device(void)
 {
 #ifdef CONFIG_SYS_USE_MMC
@@ -34,12 +68,14 @@ u32 spl_boot_device(void)
 #endif
 	return BOOT_DEVICE_NONE;
 }
+#endif
 
 u32 spl_boot_mode(void)
 {
 	switch (spl_boot_device()) {
 #ifdef CONFIG_SYS_USE_MMC
 	case BOOT_DEVICE_MMC1:
+	case BOOT_DEVICE_MMC2:
 		return MMCSD_MODE_FS;
 		break;
 #endif