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authorRussell King <rmk@dyn-67.arm.linux.org.uk>2005-12-14 09:57:35 -0500
committerRussell King <rmk+kernel@arm.linux.org.uk>2005-12-14 09:57:35 -0500
commit45f8245b972e360c19aec9032e2a2033b8ac3719 (patch)
treee271207855406f5fb117126efd23cada5122456c /drivers/mmc/mmc.c
parentcd6104572bca9e4afe0dcdb8ecd65ef90b01297b (diff)
[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: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'drivers/mmc/mmc.c')
-rw-r--r--drivers/mmc/mmc.c10
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)
679} 679}
680 680
681/* 681/*
682 * Apply power to the MMC stack. 682 * Apply power to the MMC stack. This is a two-stage process.
683 * First, we enable power to the card without the clock running.
684 * We then wait a bit for the power to stabilise. Finally,
685 * enable the bus drivers and clock to the card.
686 *
687 * We must _NOT_ enable the clock prior to power stablising.
688 *
689 * If a host does all the power sequencing itself, ignore the
690 * initial MMC_POWER_UP stage.
683 */ 691 */
684static void mmc_power_up(struct mmc_host *host) 692static void mmc_power_up(struct mmc_host *host)
685{ 693{