board: st: stm32mp2: add mmc_get_env_dev()

Use the boot instance to select the correct mmc device identifier,
this patch only to save the environment on eMMC = MMC(1) on
STMicroelectronics boards.

Set the CONFIG_SYS_MMC_ENV_DEV to -1 to select the mmc boot instance
by default.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>

board/st/stm32mp2/stm32mp2.c

@@ -10,6 +10,7 @@
 #include <fdt_support.h>
 #include <log.h>
 #include <misc.h>
+#include <mmc.h>
 #include <asm/global_data.h>
 #include <asm/arch/sys_proto.h>
 #include <dm/device.h>
@@ -78,6 +79,42 @@ enum env_location env_get_location(enum env_operation op, int prio)
 	}
 }
 
+int mmc_get_boot(void)
+{
+	struct udevice *dev;
+	u32 boot_mode = get_bootmode();
+	unsigned int instance = (boot_mode & TAMP_BOOT_INSTANCE_MASK) - 1;
+	char cmd[20];
+	const u32 sdmmc_addr[] = {
+		STM32_SDMMC1_BASE,
+		STM32_SDMMC2_BASE,
+		STM32_SDMMC3_BASE
+	};
+
+	if (instance > ARRAY_SIZE(sdmmc_addr))
+		return 0;
+
+	/* search associated sdmmc node in devicetree */
+	snprintf(cmd, sizeof(cmd), "mmc@%x", sdmmc_addr[instance]);
+	if (uclass_get_device_by_name(UCLASS_MMC, cmd, &dev)) {
+		log_err("mmc%d = %s not found in device tree!\n", instance, cmd);
+		return 0;
+	}
+
+	return dev_seq(dev);
+};
+
+int mmc_get_env_dev(void)
+{
+	const int mmc_env_dev = CONFIG_IS_ENABLED(ENV_IS_IN_MMC, (CONFIG_SYS_MMC_ENV_DEV), (-1));
+
+	if (mmc_env_dev >= 0)
+		return mmc_env_dev;
+
+	/* use boot instance to select the correct mmc device identifier */
+	return mmc_get_boot();
+}
+
 int board_late_init(void)
 {
 	const void *fdt_compat;

configs/stm32mp25_defconfig

@@ -36,7 +36,7 @@ CONFIG_CMD_LOG=y
 CONFIG_OF_LIVE=y
 CONFIG_ENV_IS_NOWHERE=y
 CONFIG_ENV_IS_IN_MMC=y
-CONFIG_SYS_MMC_ENV_DEV=1
+CONFIG_SYS_MMC_ENV_DEV=-1
 CONFIG_NO_NET=y
 CONFIG_SYS_64BIT_LBA=y
 CONFIG_GPIO_HOG=y