Commit 45f8245b authored by Russell King's avatar Russell King Committed by Russell King

[MMC] Explain the internals of mmc_power_up()

It seems that people get confused about what is happening in
mmc_power_up().  Add a comment to make it clear why we have
a two stage process.
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent cd610457
...@@ -679,7 +679,15 @@ static void mmc_idle_cards(struct mmc_host *host) ...@@ -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) static void mmc_power_up(struct mmc_host *host)
{ {
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment