| Message ID | 1390906213-7612-1-git-send-email-Vincent.Yang@tw.fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 28 January 2014 11:50, Vincent Yang <vincent.yang.fujitsu@gmail.com> wrote: > When switching the signal voltage from 3.3V to 1.8V, there should be only > one SD Clock gating and un-gating operation. Between them the SD host > controller should switch signal level to 1.8V. > However, sometimes there is an additional gating and un-gating operation > immediately after CMD11. This operation can cause some UHS-I cards report > failure by holding DAT[3:0] low. It is because CONFIG_MMC_CLKGATE attempts > to aggressively gate the clock for power saving. > > This patch is going to hold SD Clock before CMD11, therefore, the additional > gating and un-gating operation can be prevented. It has been verified on > some UHS-I SD memory cards and works correctly. Acked-by: Ulf Hansson <ulf.hansson@linaro.org> > --- > 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 098374b..86a35ef 100644 > --- a/drivers/mmc/core/core.c > +++ b/drivers/mmc/core/core.c > @@ -1432,6 +1432,8 @@ 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; > @@ -1442,8 +1444,6 @@ 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 > -- > 1.7.9.5 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 098374b..86a35ef 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -1432,6 +1432,8 @@ 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; @@ -1442,8 +1444,6 @@ 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