[PATCH v2 1/3] board: samsung: exynos-mobile: use blkmap for booting from userdata subpartitions

[Kaustabh Chakraborty]

Some distributions tend to provide a single combined image with EFS and
the system root filesystem. Flashing it as-is in a single partition
(usually done in userdata partition as it is the largest) is not
bootable as U-Boot does not understand subpartitions.

Use blkmap to map the userdata partition into its own block device.

Signed-off-by: Kaustabh Chakraborty <kauschluss at disroot.org>
---
 board/samsung/exynos-mobile/exynos-mobile.c   | 45 +++++++++++++++++++++++++++
 board/samsung/exynos-mobile/exynos-mobile.env |  5 +++
 configs/exynos-mobile_defconfig               |  4 ++-
 3 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/board/samsung/exynos-mobile/exynos-mobile.c b/board/samsung/exynos-mobile/exynos-mobile.c
index 1f61f28de5f..c5e1b186ae3 100644
--- a/board/samsung/exynos-mobile/exynos-mobile.c
+++ b/board/samsung/exynos-mobile/exynos-mobile.c
@@ -184,6 +184,45 @@ static void exynos_env_setup(void)
 	env_set("fdtfile", buf);
 }
 
+static int exynos_blk_env_setup(void)
+{
+	const char *blk_ifname;
+	int blk_dev = 0;
+	struct blk_desc *blk_desc;
+	struct disk_partition info = {0};
+	unsigned long largest_part_start = 0, largest_part_size = 0;
+	int i;
+
+	blk_ifname = "mmc";
+	blk_desc = blk_get_dev(blk_ifname, blk_dev);
+	if (!blk_desc) {
+		log_err("%s: required mmc device not available\n", __func__);
+		return -ENODEV;
+	}
+
+	for (i = 1; i < CONFIG_EFI_PARTITION_ENTRIES_NUMBERS; i++) {
+		if (part_get_info(blk_desc, i, &info))
+			continue;
+
+		if (info.start > largest_part_size) {
+			largest_part_start = info.start;
+			largest_part_size = info.size;
+		}
+	}
+
+	if (largest_part_size) {
+		env_set("blkmap_blk_ifname", blk_ifname);
+		env_set_ulong("blkmap_blk_dev", blk_dev);
+		env_set_ulong("blkmap_blk_nr", largest_part_start);
+		env_set_hex("blkmap_size_r", largest_part_size);
+	} else {
+		log_warning("%s: no qualified partition for blkmap, skipping\n",
+			    __func__);
+	}
+
+	return 0;
+}
+
 static int exynos_fastboot_setup(void)
 {
 	struct blk_desc *blk_dev;
@@ -297,7 +336,13 @@ int board_init(void)
 
 int misc_init_r(void)
 {
+	int ret;
+
 	exynos_env_setup();
 
+	ret = exynos_blk_env_setup();
+	if (ret)
+		return ret;
+
 	return exynos_fastboot_setup();
 }
diff --git a/board/samsung/exynos-mobile/exynos-mobile.env b/board/samsung/exynos-mobile/exynos-mobile.env
index aa2e89afbac..33f767319b5 100644
--- a/board/samsung/exynos-mobile/exynos-mobile.env
+++ b/board/samsung/exynos-mobile/exynos-mobile.env
@@ -2,6 +2,11 @@ stdin=serial,button-kbd
 stdout=serial,vidconsole
 stderr=serial,vidconsole
 
+blkmapcmd=blkmap create root;
+	  blkmap map root 0 ${blkmap_size_r} linear ${blkmap_blk_ifname} ${blkmap_blk_dev} ${blkmap_blk_nr}
+
+preboot=run blkmapcmd
+
 bootdelay=0
 bootcmd=bootefi bootmgr; pause; bootmenu
 
diff --git a/configs/exynos-mobile_defconfig b/configs/exynos-mobile_defconfig
index c7d206f94ac..cee468d9c24 100644
--- a/configs/exynos-mobile_defconfig
+++ b/configs/exynos-mobile_defconfig
@@ -12,6 +12,7 @@ CONFIG_SYS_LOAD_ADDR=0x80000000
 CONFIG_ARMV8_CNTFRQ_BROKEN=y
 # CONFIG_PSCI_RESET is not set
 CONFIG_BUTTON_CMD=y
+CONFIG_USE_PREBOOT=y
 CONFIG_SAVE_PREV_BL_FDT_ADDR=y
 CONFIG_SAVE_PREV_BL_INITRAMFS_START_ADDR=y
 CONFIG_SYS_PBSIZE=1024
@@ -24,8 +25,9 @@ CONFIG_CMD_POWEROFF=y
 CONFIG_CMD_FS_GENERIC=y
 CONFIG_EFI_PARTITION=y
 CONFIG_OF_UPSTREAM=y
-CONFIG_OF_BOARD=y
 CONFIG_OF_UPSTREAM_BUILD_VENDOR=y
+CONFIG_OF_BOARD=y
+CONFIG_BLKMAP=y
 CONFIG_BUTTON=y
 CONFIG_BUTTON_REMAP_PHONE_KEYS=y
 CONFIG_CLK_EXYNOS7870=y

-- 
2.52.0