From 02f3029f1810b99869254d0cf0a71946a008a728 Mon Sep 17 00:00:00 2001 From: Lei Wen Date: Fri, 2 Sep 2011 17:34:17 +0000 Subject: [PATCH] mmc: retry the cmd8 to meet 74 clocks requirement in the spec For some controller it has dynamic clock gating, and only toggle out clk when the first cmd0 send out, while some card strictly obey the 74 clocks rule, the interval may not be sufficient between the cmd0 and this cmd8, retry to fulfil the clock requirement. Signed-off-by: Lei Wen Tested-by: Marek Vasut --- drivers/mmc/mmc.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c index e5fedb3951..3f59687536 100644 --- a/drivers/mmc/mmc.c +++ b/drivers/mmc/mmc.c @@ -1179,7 +1179,7 @@ block_dev_desc_t *mmc_get_dev(int dev) int mmc_init(struct mmc *mmc) { - int err; + int err, retry = 3; if (mmc->has_init) return 0; @@ -1202,7 +1202,19 @@ int mmc_init(struct mmc *mmc) mmc->part_num = 0; /* Test for SD version 2 */ - err = mmc_send_if_cond(mmc); + /* + * retry here for 3 times, as for some controller it has dynamic + * clock gating, and only toggle out clk when the first cmd0 send + * out, while some card strictly obey the 74 clocks rule, the interval + * may not be sufficient between the cmd0 and this cmd8, retry to + * fulfil the clock requirement + */ + do { + err = mmc_send_if_cond(mmc); + } while (--retry > 0 && err); + + if (err) + return err; /* Now try to get the SD card's operating condition */ err = sd_send_op_cond(mmc); -- 2.30.2