diff options
Diffstat (limited to 'drivers/mmc')
| -rw-r--r-- | drivers/mmc/mmc.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c index b586a83a9b4c..eb41391e06e9 100644 --- a/drivers/mmc/mmc.c +++ b/drivers/mmc/mmc.c @@ -679,7 +679,15 @@ static void mmc_idle_cards(struct mmc_host *host) } /* - * Apply power to the MMC stack. + * Apply power to the MMC stack. This is a two-stage process. + * First, we enable power to the card without the clock running. + * We then wait a bit for the power to stabilise. Finally, + * enable the bus drivers and clock to the card. + * + * We must _NOT_ enable the clock prior to power stablising. + * + * If a host does all the power sequencing itself, ignore the + * initial MMC_POWER_UP stage. */ static void mmc_power_up(struct mmc_host *host) { |