| Message ID | 20221028073740.7259-1-yann.gautier@foss.st.com |
|---|---|
| State | New |
| Headers | show |
| Series | mmc: core: properly select voltage range without power cycle | expand |
On Fri, 28 Oct 2022 at 09:38, Yann Gautier <yann.gautier@foss.st.com> wrote: > > In mmc_select_voltage(), if there is no full power cycle, the voltage > range selected at the end of the function will be on a single range > (e.g. 3.3V/3.4V). To keep a range around the selected voltage (3.2V/3.4V), > the mask shift should be reduced by 1. > > This issue was triggered by using a specific SD-card (Verbatim Premium > 16GB UHS-1) on an STM32MP157C-DK2 board. This board cannot do UHS modes > and there is no power cycle. And the card was failing to switch to > high-speed mode. When adding the range 3.2V/3.3V for this card with the > proposed shift change, the card can switch to high-speed mode. > > Fixes: ce69d37b7d8f ("mmc: core: Prevent violation of specs while initializing cards") > Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> Applied for next and by adding a stable tag, thanks! Kind regards Uffe > --- > drivers/mmc/core/core.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > index 95fa8fb1d45f..c5de202f530a 100644 > --- a/drivers/mmc/core/core.c > +++ b/drivers/mmc/core/core.c > @@ -1134,7 +1134,13 @@ u32 mmc_select_voltage(struct mmc_host *host, u32 ocr) > mmc_power_cycle(host, ocr); > } else { > bit = fls(ocr) - 1; > - ocr &= 3 << bit; > + /* > + * The bit variable represents the highest voltage bit set in > + * the OCR register. > + * To keep a range of 2 values (e.g. 3.2V/3.3V and 3.3V/3.4V), > + * we must shift the mask '3' with (bit - 1). > + */ > + ocr &= 3 << (bit - 1); > if (bit != host->ios.vdd) > dev_warn(mmc_dev(host), "exceeding card's volts\n"); > } > -- > 2.25.1 >
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 95fa8fb1d45f..c5de202f530a 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -1134,7 +1134,13 @@ u32 mmc_select_voltage(struct mmc_host *host, u32 ocr) mmc_power_cycle(host, ocr); } else { bit = fls(ocr) - 1; - ocr &= 3 << bit; + /* + * The bit variable represents the highest voltage bit set in + * the OCR register. + * To keep a range of 2 values (e.g. 3.2V/3.3V and 3.3V/3.4V), + * we must shift the mask '3' with (bit - 1). + */ + ocr &= 3 << (bit - 1); if (bit != host->ios.vdd) dev_warn(mmc_dev(host), "exceeding card's volts\n"); }
In mmc_select_voltage(), if there is no full power cycle, the voltage range selected at the end of the function will be on a single range (e.g. 3.3V/3.4V). To keep a range around the selected voltage (3.2V/3.4V), the mask shift should be reduced by 1. This issue was triggered by using a specific SD-card (Verbatim Premium 16GB UHS-1) on an STM32MP157C-DK2 board. This board cannot do UHS modes and there is no power cycle. And the card was failing to switch to high-speed mode. When adding the range 3.2V/3.3V for this card with the proposed shift change, the card can switch to high-speed mode. Fixes: ce69d37b7d8f ("mmc: core: Prevent violation of specs while initializing cards") Signed-off-by: Yann Gautier <yann.gautier@foss.st.com> --- drivers/mmc/core/core.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)