On 7/5/2026 11:37 AM, Eric Chung wrote:
Enable the host controller's support for the CMD23 (SET_BLOCK_COUNT)
command to manage multi-block read/write operations. This allows the
MMC core to use CMD23 in preference to the legacy CMD18/CMD25 plus
CMD12 sequence, reducing command overhead and improving I/O
performance on multi-block transfers.
The commit message claims this enables "host controller" support, but the
changes are entirely in the MMC core (mmc.c) and header. No SDHCI host
driver sets MMC_CAP_CMD23 in this patch. mmc_write_blocks() in
mmc_write.c is not touched. CMD25 still always follows with CMD12.
Signed-off-by: Eric Chung <[email protected]>
---
v3:
- Avoid to use quirk to enable CMD23. Use capability instead.
---
drivers/mmc/mmc.c | 18 ++++++++++++++----
include/mmc.h | 6 +++++-
2 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index f0e38efb262..bc8e9ee6d1c 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -461,6 +461,14 @@ static int mmc_read_blocks(struct mmc *mmc, void *dst,
lbaint_t start,
struct mmc_cmd cmd;
struct mmc_data data;
+ if (mmc->host_caps & MMC_CAP_CMD23) {
+ cmd.cmdidx = MMC_CMD_SET_BLOCK_COUNT;
+ cmd.cmdarg = blkcnt & 0x0000ffff;
+ cmd.resp_type = MMC_RSP_R1;
+ if (mmc_send_cmd(mmc, &cmd, NULL))
+ return 0;
+ }
+
CMD23 is only meaningful before CMD18 (multi-block read). Sending it before
CMD17 (single block, blkcnt == 1) is undefined per the SD spec, which
states: "SET_BLOCK_COUNT - Specify block count for CMD18 and CMD25."
The guard must be:
if (blkcnt > 1 && (mmc->host_caps & MMC_CAP_CMD23)) {
if (blkcnt > 1)
cmd.cmdidx = MMC_CMD_READ_MULTIPLE_BLOCK;
else
@@ -481,7 +489,7 @@ static int mmc_read_blocks(struct mmc *mmc, void *dst,
lbaint_t start,
if (mmc_send_cmd(mmc, &cmd, &data))
return 0;
- if (blkcnt > 1) {
+ if (blkcnt > 1 && !(mmc->host_caps & MMC_CAP_CMD23)) {
if (mmc_send_stop_transmission(mmc, false)) {
#if !defined(CONFIG_XPL_BUILD) || defined(CONFIG_SPL_LIBCOMMON_SUPPORT)
log_err("mmc fail to send stop cmd\n");
@@ -1436,6 +1444,8 @@ static int sd_get_capabilities(struct mmc *mmc)
if (mmc->scr[0] & SD_DATA_4BIT)
mmc->card_caps |= MMC_MODE_4BIT;
+ if (!(mmc->scr[0] & SD_SCR_CMD23_SUPPORT))
+ mmc->host_caps &= ~MMC_CAP_CMD23;
Clearing CMD23 capability when the card does not advertise support via
SCR[33] only for SD cards via sd_get_capabilities()but for eMMC the
MMC_CAP_CMD23 flag set by the host driver will remain unconditionally.
Similar handing should be done in mmc_get_capabilities().
/* Version 1.0 doesn't support switching */
if (mmc->version == SD_VERSION_1_0)
@@ -2963,9 +2973,9 @@ int mmc_get_op_cond(struct mmc *mmc, bool quiet)
return err;
#ifdef CONFIG_MMC_QUIRKS
- mmc->quirks = MMC_QUIRK_RETRY_SET_BLOCKLEN |
- MMC_QUIRK_RETRY_SEND_CID |
- MMC_QUIRK_RETRY_APP_CMD;
+ mmc->quirks |= MMC_QUIRK_RETRY_SET_BLOCKLEN |
+ MMC_QUIRK_RETRY_SEND_CID |
+ MMC_QUIRK_RETRY_APP_CMD;
Unrelated to CMD23 support.
#endif
err = mmc_power_cycle(mmc);
diff --git a/include/mmc.h b/include/mmc.h
index 9509c9e9543..b663da71019 100644
--- a/include/mmc.h
+++ b/include/mmc.h
@@ -67,6 +67,7 @@ struct bd_info;
#define MMC_CAP_NONREMOVABLE BIT(14)
#define MMC_CAP_NEEDS_POLL BIT(15)
#define MMC_CAP_CD_ACTIVE_HIGH BIT(16)
+#define MMC_CAP_CMD23 BIT(17)
#define MMC_MODE_8BIT BIT(30)
#define MMC_MODE_4BIT BIT(29)
@@ -141,6 +142,8 @@ static inline bool mmc_is_tuning_cmd(uint cmdidx)
#define SD_HIGHSPEED_BUSY 0x00020000
#define SD_HIGHSPEED_SUPPORTED 0x00020000
+#define SD_SCR_CMD23_SUPPORT BIT(1)
+
#define UHS_SDR12_BUS_SPEED 0
#define HIGH_SPEED_BUS_SPEED 1
#define UHS_SDR25_BUS_SPEED 1
@@ -343,7 +346,8 @@ static inline bool mmc_is_tuning_cmd(uint cmdidx)
#define MMC_QUIRK_RETRY_SEND_CID BIT(0)
#define MMC_QUIRK_RETRY_SET_BLOCKLEN BIT(1)
-#define MMC_QUIRK_RETRY_APP_CMD BIT(2)
+#define MMC_QUIRK_RETRY_APP_CMD BIT(2)
+#define MMC_QUIRK_BLK_CMD23 BIT(3)
BLK_CMD23 quirk leftover from the previous patch
Regards,
Tanmay Kathpalia
