Re: [PATCH v2 RESEND 2/6] mmc: rtsx_usb_sdmmc: start card power-up at 3.3V

[Sean Rhodes]

> Right?

Yes, that's right


On Tue, 24 Mar 2026 at 11:42, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>
> On Thu, 12 Mar 2026 at 13:16, Sean Rhodes <sean@starlabs.systems> wrote:
> >
> > Some tray-based readers keep SD_CD asserted even without a card. The
> > rtsx_usb_sdmmc driver now validates insertion with a minimal probe
> > sequence. That probe must start with the SD pads in 3.3V mode.
> >
> > Like the old rts5139 driver (sd_init_power()), force the SD pads to
> > 3.3V and tune the SD18 regulator to 3.3V before powering up the card.
> > This avoids spurious probe timeouts when the reader is left in 1.8V
> > from a previous UHS session.
> >
> > Tested: Realtek RTS5129 (0bda:0129) + tray + Lexar 2TB SDXC
> > Tested: cold boot detects mmcblk0 (2026-02-24)
> > Tested: hotplug insert enumerates mmcblk0 (2026-02-23)
> > Signed-off-by: Sean Rhodes <sean@starlabs.systems>
> > ---
> >  drivers/mmc/host/rtsx_usb_sdmmc.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/mmc/host/rtsx_usb_sdmmc.c b/drivers/mmc/host/rtsx_usb_sdmmc.c
> > index ec3eeea78e95..6be98926387d 100644
> > --- a/drivers/mmc/host/rtsx_usb_sdmmc.c
> > +++ b/drivers/mmc/host/rtsx_usb_sdmmc.c
> > @@ -1108,6 +1108,11 @@ static int sd_power_on(struct rtsx_usb_sdmmc *host)
> >         }
> >         dev_dbg(sdmmc_dev(host), "%s\n", __func__);
> >         rtsx_usb_init_cmd(ucr);
> > +       /* Start SD init at 3.3V, like the old rts5139 driver. */
> > +       rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, SD_PAD_CTL,
> > +                        SD_IO_USING_1V8, SD_IO_USING_3V3);
> > +       rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, LDO_POWER_CFG,
> > +                        TUNE_SD18_MASK, TUNE_SD18_3V3);
>
> Ideally this should be managed by the ->start_signal_voltage_switch()
> callback that is set to sdmmc_switch_voltage().
>
> However, I understand that you may need this because of patch1, and
> because mmc_power_up() first calls mmc_set_initial_state() before it
> calls mmc_set_initial_signal_voltage().
>
> Right?
>
> >         rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_SELECT, 0x07, SD_MOD_SEL);
> >         rtsx_usb_add_cmd(ucr, WRITE_REG_CMD, CARD_SHARE_MODE,
> >                         CARD_SHARE_MASK, CARD_SHARE_SD);
> > --
> > 2.51.0
>
> Kind regards
> Uffe