arm64: mvebu: armada-8k: support environment in SD/eMMC

Detect the SD/eMMC boot device at run-time. Load the environment from
the boot deice, as well as save to it.

Leave the environment offset the same as in the SPI flash.

Make SD/eMMC 0 the default environment device when the boot device is
not detected.

Cc: Konstantin Porotchkin <kostap@marvell.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Stefan Roese <sr@denx.de>

arch/arm/mach-mvebu/armada8k/cpu.c

@@ -18,6 +18,10 @@
 #define RFU_GLOBAL_SW_RST		(MVEBU_RFU_BASE + 0x84)
 #define RFU_SW_RESET_OFFSET		0
 
+#define SAR0_REG			(MVEBU_REGISTER(0x2400200))
+#define BOOT_MODE_MASK			0x3f
+#define BOOT_MODE_OFFSET		4
+
 /*
  * The following table includes all memory regions for Armada 7k and
  * 8k SoCs. The Armada 7k is missing the CP110 slave regions here. Lets
@@ -125,3 +129,23 @@ u32 mvebu_get_nand_clock(void)
 	else
 		return 250 * 1000000;
 }
+
+int mmc_get_env_dev(void)
+{
+	u32 reg;
+	unsigned int boot_mode;
+
+	reg = readl(SAR0_REG);
+	boot_mode = (reg >> BOOT_MODE_OFFSET) & BOOT_MODE_MASK;
+
+	switch (boot_mode) {
+	case 0x28:
+	case 0x2a:
+		return 0;
+	case 0x29:
+	case 0x2b:
+		return 1;
+	}
+
+	return CONFIG_SYS_MMC_ENV_DEV;
+}

include/configs/mvebu_armada-8k.h

@@ -64,6 +64,9 @@
 #define CONFIG_ENV_SIZE			(64 << 10) /* 64KiB */
 #define CONFIG_ENV_SECT_SIZE		(64 << 10) /* 64KiB sectors */
 
+/* When runtime detection fails this is the default */
+#define CONFIG_SYS_MMC_ENV_DEV		0
+
 #define CONFIG_SYS_MAX_NAND_DEVICE	1
 #define CONFIG_SYS_NAND_MAX_CHIPS	1
 #define CONFIG_SYS_NAND_ONFI_DETECTION