[PATCH v2 u-boot] 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>
---
Changes in v2:
* Disable showing warning on sama5d2_xplained due to size restrictions
---
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/Kconfig   |  7 +++++++
 common/spl/spl_mmc.c | 46 ++++++++++++++++++++++++++++++++++++--------
 2 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index 865571d4579c..0574d22b3b25 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -855,6 +855,13 @@ config SPL_MMC_WRITE
 	help
 	  Enable write access to MMC and SD Cards in SPL
 
+config SPL_MMC_WARNINGS
+	bool "Print MMC warnings"
+	depends on SPL_MMC
+	default y if !TARGET_SAMA5D2_XPLAINED
+	help
+	  Print SPL MMC warnings. You can disable this option to reduce SPL size.
+
 
 config SPL_MPC8XXX_INIT_DDR
 	bool "Support MPC8XXX DDR init"
diff --git a/common/spl/spl_mmc.c b/common/spl/spl_mmc.c
index f7a42a11477d..ec424ceded0e 100644
--- a/common/spl/spl_mmc.c
+++ b/common/spl/spl_mmc.c
@@ -408,15 +408,45 @@ 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
+#ifdef CONFIG_SPL_MMC_WARNINGS
+			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");
+#else
+			puts("spl: mmc: fallback to user area\n");
+#endif
+#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
+#ifdef CONFIG_SPL_MMC_WARNINGS
+			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");
+#else
+			puts("spl: mmc: fallback to user area\n");
+#endif
+#endif
+			part = 0;
+			break;
+		}
+	}
 #endif
 	return part;
 }
-- 
2.20.1