diff options
| author | Ian Molton <ian@mnementh.co.uk> | 2009-09-30 21:41:52 +0100 |
|---|---|---|
| committer | Ian Molton <ian@mnementh.co.uk> | 2009-10-04 18:16:34 +0100 |
| commit | 4b52cd752af330463abf2527a8b0df9a10916613 (patch) | |
| tree | 9184561a3dccdd320cb46ef1130ef74bcc693678 | |
| parent | ac34a9ad8288a0cd2fd7b846622e509fbad694f7 (diff) | |
MMC: core: Lower MMC/SD init frequency.
This patch lowers the previously imposed limit for MMC / SD card
initialisation.
Some cards are a little 'out of spec' in that they wont initialise over
about 200kHz (one such card works fine at 20MHz once initialised).
Spec says init must occur below 400kHz. This patch lowers this to
64kHz and fixes the regression caused by the previous limit, whilst not
breaking the specs.
Signed-off-by: Ian Molton <ian@mnementh.co.uk>
| -rw-r--r-- | drivers/mmc/core/core.c | 4 | ||||
| -rw-r--r-- | drivers/mmc/core/core.h | 10 |
2 files changed, 12 insertions, 2 deletions
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index d84c880fac84..5cb0df45bd24 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -708,12 +708,12 @@ static void mmc_power_up(struct mmc_host *host) */ mmc_delay(10); - if (host->f_min > 400000) { + if (host->f_min > MMC_INIT_FREQ) { pr_warning("%s: Minimum clock frequency too high for " "identification mode\n", mmc_hostname(host)); host->ios.clock = host->f_min; } else - host->ios.clock = 400000; + host->ios.clock = MMC_INIT_FREQ; host->ios.power_mode = MMC_POWER_ON; mmc_set_ios(host); diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h index c819effa1032..96505f0c82e2 100644 --- a/drivers/mmc/core/core.h +++ b/drivers/mmc/core/core.h @@ -15,6 +15,16 @@ #define MMC_CMD_RETRIES 3 +/* Spec says initialisation must happen at or below 400kHz. + * Some MMC cards fail to initialise at 400kHz (even as low as 200kHz) and + * Some host controllers (eg. tmio_mmc) cannot garantee to set the clock below + * 400kHz (it rounds to the closest clock freq available). + * + * 64 kHz seems like a good speed/reliability compromise. + */ + +#define MMC_INIT_FREQ 64000 + struct mmc_bus_ops { void (*remove)(struct mmc_host *); void (*detect)(struct mmc_host *); |