[PATCH] mmc: allow forward compatibility for EXT_CSD_REV

[박민우 (MW Park)]

[PATCH] mmc: allow forward compatibility for EXT_CSD_REV

According to the JEDEC Standard, the EXT_CSD format is meant to be
forward compatible. As long as CSD_STRUCTURE does not change, all
values for EXT_CSD_REV are authorized.

Currently, if an eMMC device with a newer EXT_CSD_REV (e.g., eMMC 5.1B
with EXT_CSD_REV=9) is used, U-Boot fails to initialize it and returns
-EINVAL because the revision is larger than the mmc_versions array size.

Fix this by falling back to the latest supported version if the
EXT_CSD_REV exceeds the known versions. This ensures forward
compatibility with future eMMC specifications.

Signed-off-by: MW Park <mw.park at telechips.com>
---
 drivers/mmc/mmc.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index c5705f4f215..dbec728a474 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -2334,6 +2334,7 @@ static int mmc_startup_v4(struct mmc *mmc)
         u64 capacity;
         bool has_parts = false;
         bool part_completed;
+       u8 rev;
         static const u32 mmc_versions[] = {
                 MMC_VERSION_4,
                 MMC_VERSION_4_1,
@@ -2380,12 +2381,19 @@ static int mmc_startup_v4(struct mmc *mmc)
                 return -ENOMEM;
         memcpy(mmc->ext_csd, ext_csd, MMC_MAX_BLOCK_LEN);
 #endif
-       if (ext_csd[EXT_CSD_REV] >= ARRAY_SIZE(mmc_versions)) {
-               err = -EINVAL;
-               goto error;
-       }
+       rev = ext_csd[EXT_CSD_REV];
+
+       /*
+        * According to the JEDEC Standard, the EXT_CSD format is meant to be
+        * forward compatible. As long as CSD_STRUCTURE does not change, all
+        * values for EXT_CSD_REV are authorized.
+        * If the EXT_CSD_REV exceeds the known versions, fallback to the
+        * latest supported version instead of returning an error.
+        */
+       if (rev >= ARRAY_SIZE(mmc_versions))
+               rev = ARRAY_SIZE(mmc_versions) - 1;

-       mmc->version = mmc_versions[ext_csd[EXT_CSD_REV]];
+       mmc->version = mmc_versions[rev];

         if (mmc->version >= MMC_VERSION_4_2) {
                 /*
--
2.34.1
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