[PATCH 4/4] mmc: core: hold SD Clock before CMD11 during Signal
From: Ulf Hansson <hidden>
Date: 2014-11-24 09:56:28
Also in:
linux-mmc
On 21 November 2014 at 01:51, Vincent Yang [off-list ref] wrote:
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 <redacted>
Thanks! Applied for next. Kind regards Uffe
quoted hunk ↗ jump to hunk
--- drivers/mmc/core/core.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index f26a5f1..8b9e2cfd 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c@@ -1420,18 +1420,20 @@ 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@@ -1480,6 +1482,7 @@ power_cycle: mmc_power_cycle(host, ocr); } +err_command: mmc_host_clk_release(host); return err; --1.9.0