diff options
| author | Christoph Stoidner <[email protected]> | 2025-10-31 15:59:51 +0100 |
|---|---|---|
| committer | Peng Fan <[email protected]> | 2026-01-08 21:57:20 +0800 |
| commit | 21cdfd199220cd259b5b7d472cee0577b7eb8eca (patch) | |
| tree | ecc27add6842bc2dbba370a495a93cb44030e1b0 /drivers | |
| parent | 141be72e2a9d43aa4e3d1a6a6e0ab8f9eb8784c6 (diff) | |
mmc: Fix missing 1 ms delay after mmc power up
mmc/sd specification requires a 1 ms delay (stable supply voltage)
after vdd was enabled and before issuing first command.
For most sdcard/soc combinations, the missing delay seems to be not a
problem because the processing time between enabling vdd and the first
command is often hundreds of microseconds or more. However, in our
specific case, some sdcards were not detected by u-boot:
* soc: NXP i.MX 93
* sdcards: SanDisk Ultra, 64GB micro SDXC 1,
MediaRange, 8GB, SDHC
* measured time between vdd and first command: approx. 784us
* symptom: both sdcards did not respond at all to first commands,
u-boot mmc subsystem ran into timeout and stops to
initialize the cards
Signed-off-by: Christoph Stoidner <[email protected]>
Cc: Peng Fan <[email protected]>
Cc: Jaehoon Chung <[email protected]>
Signed-off-by: Peng Fan <[email protected]>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/mmc/mmc.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c index bf82c515600..71664173016 100644 --- a/drivers/mmc/mmc.c +++ b/drivers/mmc/mmc.c @@ -2933,11 +2933,18 @@ static int mmc_power_cycle(struct mmc *mmc) return ret; /* - * SD spec recommends at least 1ms of delay. Let's wait for 2ms - * to be on the safer side. + * SD spec recommends at least 1ms of 'power on' delay. + * Let's wait for 2ms to be on the safer side. */ udelay(2000); - return mmc_power_on(mmc); + ret = mmc_power_on(mmc); + + /* + * SD spec recommends at least 1ms of 'stable supply voltage' delay. + * Let's wait for 2ms to be on the safer side. + */ + udelay(2000); + return ret; } int mmc_get_op_cond(struct mmc *mmc, bool quiet) |