[PATCH u-boot 1/4] mmc: spl: Make partition choice in default_spl_mmc_emmc_boot_partition() more explicit

[Pali Rohár]

To make eMMC partition choosing in default_spl_mmc_emmc_boot_partition()
function better understandable, rewrite it via explicit switch-case code
pattern.

Also add a warning when eMMC EXT_CSD[179] register is configured by user to
value which is not suitable for eMMC booting and SPL do not know how to
interpret it.

Note that when booting from eMMC device via EXT_CSD[179] register is
explicitly disabled then SPL still loads and boots from this eMMC device
from User Area partition. This behavior was not changed in this commit and
should be revisited in the future.

Signed-off-by: Pali Rohár <pali at kernel.org>

---
This patch depends on another patch:
mmc: spl: Add comments for default_spl_mmc_emmc_boot_partition()
https://patchwork.ozlabs.org/project/uboot/patch/20230404202805.8523-1-pali@kernel.org/
---
 common/spl/spl_mmc.c | 38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)

diff --git a/common/spl/spl_mmc.c b/common/spl/spl_mmc.c
index 2426500dbcb9..df20a75efc29 100644
--- a/common/spl/spl_mmc.c
+++ b/common/spl/spl_mmc.c
@@ -408,15 +408,37 @@ int default_spl_mmc_emmc_boot_partition(struct mmc *mmc)
 	 *
 	 * Note: See difference between EXT_CSD_EXTRACT_PARTITION_ACCESS
 	 * and EXT_CSD_EXTRACT_BOOT_PART, specially about User area value.
-	 *
-	 * FIXME: When booting from this eMMC device is explicitly
-	 * disabled then we use User area for booting. This is incorrect.
-	 * Probably we should skip this eMMC device and select the next
-	 * one for booting. Or at least throw warning about this fallback.
 	 */
-	part = EXT_CSD_EXTRACT_BOOT_PART(mmc->part_config);
-	if (part == 7)
-		part = 0;
+	if (mmc->part_config == MMCPART_NOAVAILABLE)
+		part = 0; /* If partitions are not supported then we have only User Area partition */
+	else {
+		switch(EXT_CSD_EXTRACT_BOOT_PART(mmc->part_config)) {
+		case 0: /* Booting from this eMMC device is disabled */
+#ifdef CONFIG_SPL_LIBCOMMON_SUPPORT
+			puts("spl: WARNING: Booting from this eMMC device is disabled in EXT_CSD[179] register\n");
+			puts("spl: WARNING: Continuing anyway and selecting User Area partition for booting\n");
+#endif
+			/* FIXME: This is incorrect and probably we should select next eMMC device for booting */
+			part = 0;
+			break;
+		case 1: /* Boot partition 1 is used for booting */
+			part = 1;
+			break;
+		case 2: /* Boot partition 2 is used for booting */
+			part = 2;
+			break;
+		case 7: /* User area is used for booting */
+			part = 0;
+			break;
+		default: /* Other values are reserved */
+#ifdef CONFIG_SPL_LIBCOMMON_SUPPORT
+			puts("spl: WARNING: EXT_CSD[179] register is configured to boot from Reserved value\n");
+			puts("spl: WARNING: Selecting User Area partition for booting\n");
+#endif
+			part = 0;
+			break;
+		}
+	}
 #endif
 	return part;
 }
-- 
2.20.1