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authorVincent Yang <vincent.yang.fujitsu@gmail.com>2014-11-21 08:51:40 +0800
committerUlf Hansson <ulf.hansson@linaro.org>2014-11-26 14:31:05 +0100
commitc6eb588028f8f23dae8e26312cf192f365c85b95 (patch)
tree97bc0ab1c2d1f0fb861ec6f736fc8c08ab1a9b72 /drivers/mmc
parente34d467c515f5f64e12c28fb2b15035c9b38f332 (diff)
downloadlinux-c6eb588028f8f23dae8e26312cf192f365c85b95.tar.bz2
mmc: core: hold SD Clock before CMD11 during Signal
Voltage Switch Procedure This patch is to fix an issue found on mb86s7x platforms. [symptom] There are some UHS-1 SD memory cards sometimes cannot be detected correctly, e.g., Transcend 600x SDXC 64GB UHS-1 memory card. During Signal Voltage Switch Procedure, failure to switch is indicated by the card holding DAT[3:0] low. [analysis] According to SD Host Controller Simplified Specification Version 3.00 chapter 3.6.1, the Signal Voltage Switch Procedure should be: (1) Check S18A; (2) Issue CMD11; (3) Check CMD 11 response; (4) Stop providing SD clock; (5) Check DAT[3:0] should be 0000b; (6) Set 1.8V Signal Enable; (7) Wait 5ms; (8) Check 1.8V Signal Enable; (9) Provide SD Clock; (10) Wait 1ms; (11) Check DAT[3:0] should be 1111b; (12) error handling With CONFIG_MMC_CLKGATE=y, sometimes there is one more gating/un-gating SD clock between (2) and (3). In this case, some UHS-1 SD cards will hold DAT[3:0] 0000b at (11) and thus fails Signal Voltage Switch Procedure. [solution] By mmc_host_clk_hold() before CMD11, the additional gating/un-gating SD clock between (2) and (3) can be prevented and thus no failure at (11). It has been verified with many UHS-1 SD cards on mb86s7x platforms and works correctly. Signed-off-by: Vincent Yang <Vincent.Yang@tw.fujitsu.com> Reviewed-by: Johan Rudholm <jrudholm@gmail.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Diffstat (limited to 'drivers/mmc')
-rw-r--r--drivers/mmc/core/core.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 5bda29bff8eb..9584bffa8b22 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1447,18 +1447,20 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, u32 ocr)
pr_warn("%s: cannot verify signal voltage switch\n",
mmc_hostname(host));
+ mmc_host_clk_hold(host);
+
cmd.opcode = SD_SWITCH_VOLTAGE;
cmd.arg = 0;
cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
err = mmc_wait_for_cmd(host, &cmd, 0);
if (err)
- return err;
-
- if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR))
- return -EIO;
+ goto err_command;
- mmc_host_clk_hold(host);
+ if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR)) {
+ err = -EIO;
+ goto err_command;
+ }
/*
* The card should drive cmd and dat[0:3] low immediately
* after the response of cmd11, but wait 1 ms to be sure
@@ -1507,6 +1509,7 @@ power_cycle:
mmc_power_cycle(host, ocr);
}
+err_command:
mmc_host_clk_release(host);
return err;