From: Erick Shepherd erick.shepherd@ni.com
[ Upstream commit 9510b38dc0ba358c93cbf5ee7c28820afb85937b ]
Adds the MMC_QUIRK_NO_UHS_DDR50_TUNING quirk and updates mmc_execute_tuning() to return 0 if that quirk is set. This fixes an issue on certain Swissbit SD cards that do not support DDR50 tuning where tuning requests caused I/O errors to be thrown.
Signed-off-by: Erick Shepherd erick.shepherd@ni.com Acked-by: Adrian Hunter adrian.hunter@intel.com Link: https://lore.kernel.org/r/20250331221337.1414534-1-erick.shepherd@ni.com Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org ---
**YES** This commit should be backported to stable kernel trees based on the following detailed analysis: ## Critical Hardware Compatibility Fix The commit addresses a specific and serious hardware compatibility issue where certain Swissbit SD cards (series S46-u, manufactured 01/2019) throw I/O errors during DDR50 tuning requests, particularly on Bay Trail host controllers. This represents a real-world deployed hardware issue that causes system instability. ## Code Analysis - Low Risk, High Impact **1. Minimal and Targeted Changes:** - Adds a single quirk bit (`MMC_QUIRK_NO_UHS_DDR50_TUNING`) in `include/linux/mmc/card.h` - Introduces a simple helper function `mmc_card_no_uhs_ddr50_tuning()` in `drivers/mmc/core/card.h` - Adds one specific quirk entry for the problematic Swissbit cards in `drivers/mmc/core/quirks.h` - Modifies the tuning logic in `drivers/mmc/core/sd.c` to respect the new quirk **2. Functional Impact Analysis:** The key change is in the `mmc_sd_use_tuning()` function where DDR50 tuning can now be disabled: ```c case MMC_TIMING_UHS_DDR50: return !mmc_card_no_uhs_ddr50_tuning(card); ``` This change ensures that: - DDR50 mode still functions normally - Only the tuning optimization is disabled - Cards fall back to fixed sampling clock (still functional) - No loss of core functionality, only slight performance optimization loss **3. Risk Assessment:** - **Very Low Risk**: The quirk only disables tuning optimization, not DDR50 functionality itself - **Highly Targeted**: Affects only very specific cards (Swissbit 0016G, manufactured 2019/01) - **Maintains Compatibility**: Cards remain fully functional in DDR50 mode without tuning - **No Regression Potential**: Other cards are completely unaffected ## Alignment with Stable Backport Criteria **1. Important Bugfix**: Resolves I/O errors and system instability on deployed hardware **2. Minimal Risk**: Only disables optimization feature, maintains full functionality **3. Small and Contained**: Changes are isolated to the MMC quirk system **4. No Architectural Changes**: Uses existing quirk infrastructure **5. Clear User Impact**: Fixes real-world hardware compatibility issues ## Historical Pattern Consistency This commit follows the same pattern as other successful stable backports in the MMC subsystem (like Similar Commit #2 and #5 marked "YES"), which address specific hardware quirks with minimal, targeted fixes that resolve compatibility issues without introducing new functionality or architectural changes. The commit represents exactly the type of hardware compatibility fix that stable kernel trees are designed to accommodate - resolving real issues on deployed hardware with minimal risk and maximal benefit.
drivers/mmc/core/card.h | 6 ++++++ drivers/mmc/core/quirks.h | 10 ++++++++++ drivers/mmc/core/sd.c | 32 ++++++++++++++++++++++++-------- include/linux/mmc/card.h | 1 + 4 files changed, 41 insertions(+), 8 deletions(-)
diff --git a/drivers/mmc/core/card.h b/drivers/mmc/core/card.h index 3205feb1e8ff6..9cbdd240c3a7d 100644 --- a/drivers/mmc/core/card.h +++ b/drivers/mmc/core/card.h @@ -89,6 +89,7 @@ struct mmc_fixup { #define CID_MANFID_MICRON 0x13 #define CID_MANFID_SAMSUNG 0x15 #define CID_MANFID_APACER 0x27 +#define CID_MANFID_SWISSBIT 0x5D #define CID_MANFID_KINGSTON 0x70 #define CID_MANFID_HYNIX 0x90 #define CID_MANFID_KINGSTON_SD 0x9F @@ -294,4 +295,9 @@ static inline int mmc_card_broken_sd_poweroff_notify(const struct mmc_card *c) return c->quirks & MMC_QUIRK_BROKEN_SD_POWEROFF_NOTIFY; }
+static inline int mmc_card_no_uhs_ddr50_tuning(const struct mmc_card *c) +{ + return c->quirks & MMC_QUIRK_NO_UHS_DDR50_TUNING; +} + #endif diff --git a/drivers/mmc/core/quirks.h b/drivers/mmc/core/quirks.h index 89b512905be14..7f893bafaa607 100644 --- a/drivers/mmc/core/quirks.h +++ b/drivers/mmc/core/quirks.h @@ -34,6 +34,16 @@ static const struct mmc_fixup __maybe_unused mmc_sd_fixups[] = { MMC_QUIRK_BROKEN_SD_CACHE | MMC_QUIRK_BROKEN_SD_POWEROFF_NOTIFY, EXT_CSD_REV_ANY),
+ /* + * Swissbit series S46-u cards throw I/O errors during tuning requests + * after the initial tuning request expectedly times out. This has + * only been observed on cards manufactured on 01/2019 that are using + * Bay Trail host controllers. + */ + _FIXUP_EXT("0016G", CID_MANFID_SWISSBIT, 0x5342, 2019, 1, + 0, -1ull, SDIO_ANY_ID, SDIO_ANY_ID, add_quirk_sd, + MMC_QUIRK_NO_UHS_DDR50_TUNING, EXT_CSD_REV_ANY), + END_FIXUP };
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c index 63915541c0e49..916ae9996e9d7 100644 --- a/drivers/mmc/core/sd.c +++ b/drivers/mmc/core/sd.c @@ -613,6 +613,29 @@ static int sd_set_current_limit(struct mmc_card *card, u8 *status) return 0; }
+/* + * Determine if the card should tune or not. + */ +static bool mmc_sd_use_tuning(struct mmc_card *card) +{ + /* + * SPI mode doesn't define CMD19 and tuning is only valid for SDR50 and + * SDR104 mode SD-cards. Note that tuning is mandatory for SDR104. + */ + if (mmc_host_is_spi(card->host)) + return false; + + switch (card->host->ios.timing) { + case MMC_TIMING_UHS_SDR50: + case MMC_TIMING_UHS_SDR104: + return true; + case MMC_TIMING_UHS_DDR50: + return !mmc_card_no_uhs_ddr50_tuning(card); + } + + return false; +} + /* * UHS-I specific initialization procedure */ @@ -656,14 +679,7 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card) if (err) goto out;
- /* - * SPI mode doesn't define CMD19 and tuning is only valid for SDR50 and - * SDR104 mode SD-cards. Note that tuning is mandatory for SDR104. - */ - if (!mmc_host_is_spi(card->host) && - (card->host->ios.timing == MMC_TIMING_UHS_SDR50 || - card->host->ios.timing == MMC_TIMING_UHS_DDR50 || - card->host->ios.timing == MMC_TIMING_UHS_SDR104)) { + if (mmc_sd_use_tuning(card)) { err = mmc_execute_tuning(card);
/* diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h index eb67d3d5ff5b2..2e455b20c37c2 100644 --- a/include/linux/mmc/card.h +++ b/include/linux/mmc/card.h @@ -295,6 +295,7 @@ struct mmc_card { #define MMC_QUIRK_BROKEN_SD_CACHE (1<<15) /* Disable broken SD cache support */ #define MMC_QUIRK_BROKEN_CACHE_FLUSH (1<<16) /* Don't flush cache until the write has occurred */ #define MMC_QUIRK_BROKEN_SD_POWEROFF_NOTIFY (1<<17) /* Disable broken SD poweroff notify support */ +#define MMC_QUIRK_NO_UHS_DDR50_TUNING (1<<18) /* Disable DDR50 tuning */
bool written_flag; /* Indicates eMMC has been written since power on */ bool reenable_cmdq; /* Re-enable Command Queue */