| Message ID | 1405228870-5088-5-git-send-email-Vincent.Yang@tw.fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jul 13, 2014 at 01:21:10PM +0800, Vincent Yang 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 <Vincent.Yang@tw.fujitsu.com> > --- > drivers/mmc/core/core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > index 7dc0c85..764af63 100644 > --- a/drivers/mmc/core/core.c > +++ b/drivers/mmc/core/core.c > @@ -1428,6 +1428,8 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, u32 ocr) > pr_warning("%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; > @@ -1438,8 +1440,6 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, u32 ocr) > > if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR)) > return -EIO; > - > - mmc_host_clk_hold(host); Your analysis may be correct, but implementation leads something to be desired - what happens if we exit the function just above this deleted line - returning -EIO ? Shouldn't there be some releasing of the clock hold?
>-----Original Message----- >From: Russell King - ARM Linux [mailto:linux@arm.linux.org.uk] >On Sun, Jul 13, 2014 at 01:21:10PM +0800, Vincent Yang 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 <Vincent.Yang@tw.fujitsu.com> >> --- >> drivers/mmc/core/core.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c >> index 7dc0c85..764af63 100644 >> --- a/drivers/mmc/core/core.c >> +++ b/drivers/mmc/core/core.c >> @@ -1428,6 +1428,8 @@ int mmc_set_signal_voltage(struct mmc_host *host, int >signal_voltage, u32 ocr) >> pr_warning("%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; >> @@ -1438,8 +1440,6 @@ int mmc_set_signal_voltage(struct mmc_host *host, int >signal_voltage, u32 ocr) >> >> if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR)) >> return -EIO; >> - >> - mmc_host_clk_hold(host); > >Your analysis may be correct, but implementation leads something to be >desired - what happens if we exit the function just above this deleted >line - returning -EIO ? Shouldn't there be some releasing of the >clock hold? Hi Russell, Thanks a lot for your kind help and also your review. I'll fix it in next version. Best regards, Vincent Yang > >-- >FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up >according to speedtest.net.
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 7dc0c85..764af63 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -1428,6 +1428,8 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, u32 ocr) pr_warning("%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; @@ -1438,8 +1440,6 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage, u32 ocr) if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR)) return -EIO; - - mmc_host_clk_hold(host); /* * The card should drive cmd and dat[0:3] low immediately * after the response of cmd11, but wait 1 ms to be sure
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> --- drivers/mmc/core/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)