On Fri, 28 Oct 2022 at 09:38, Yann Gautier <yann.gautier@xxxxxxxxxxx> 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@xxxxxxxxxxx>
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
>
