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

drivers/mmc/mmc.c

+9 −1
Original line number Diff line number Diff line
@@ -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)

{