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);
 	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

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

> Right?

Yes, that's right


On Tue, 24 Mar 2026 at 11:42, Ulf Hansson <ulf.hansson@linaro.org> 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