[PATCH] mmc: sdhci-of-arasan: Ensure CD logic stabilization before power-up

[Potthuri, Sai Krishna]

[Public]

Hi Adrian,

> -----Original Message-----
> From: Adrian Hunter <adrian.hunter at intel.com>
> Sent: Thursday, July 24, 2025 9:50 PM
> To: Potthuri, Sai Krishna <sai.krishna.potthuri at amd.com>; Simek, Michal
> <michal.simek at amd.com>; Ulf Hansson <ulf.hansson at linaro.org>
> Cc: linux-mmc at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org; git (AMD-Xilinx) <git at amd.com>;
> saikrishna12468 at gmail.com
> Subject: Re: [PATCH] mmc: sdhci-of-arasan: Ensure CD logic stabilization before
> power-up
>
> On 21/07/2025 12:53, Sai Krishna Potthuri wrote:
> > During SD suspend/resume without a full card rescan (when using
> > non-removable SD cards for rootfs), the SD card initialization may
> > fail after resume. This occurs because, after a host controller reset,
> > the card detect logic may take time to stabilize due to debounce logic.
> > Without waiting for stabilization, the host may attempt powering up
> > the card prematurely, leading to command timeouts during resume flow.
> > Add sdhci_arasan_set_power_and_bus_voltage() to wait for the card
> > detect stable bit before power up the card. Since the stabilization
> > time is not fixed, a maximum timeout of one second is used to ensure
> > sufficient wait time for the card detect signal to stabilize.
> >
> > Signed-off-by: Sai Krishna Potthuri <sai.krishna.potthuri at amd.com>
> > ---
> >  drivers/mmc/host/sdhci-of-arasan.c | 24 ++++++++++++++++++++++--
> >  1 file changed, 22 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-of-arasan.c
> > b/drivers/mmc/host/sdhci-of-arasan.c
> > index 42878474e56e..3ce55009ba4a 100644
> > --- a/drivers/mmc/host/sdhci-of-arasan.c
> > +++ b/drivers/mmc/host/sdhci-of-arasan.c
> > @@ -99,6 +99,9 @@
> >  #define HIWORD_UPDATE(val, mask, shift) \
> >             ((val) << (shift) | (mask) << ((shift) + 16))
> >
> > +#define CD_STABLE_TIMEOUT_US               1000000
> > +#define CD_STABLE_MAX_SLEEP_US             10
> > +
> >  /**
> >   * struct sdhci_arasan_soc_ctl_field - Field used in sdhci_arasan_soc_ctl_map
> >   *
> > @@ -514,6 +517,23 @@ static int sdhci_arasan_voltage_switch(struct
> mmc_host *mmc,
> >     return -EINVAL;
> >  }
> >
> > +static void sdhci_arasan_set_power_and_bus_voltage(struct sdhci_host *host,
> unsigned char mode,
> > +                                              unsigned short vdd)
> > +{
> > +   u32 reg;
> > +
> > +   /*
> > +    * Ensure that the card detect logic has stabilized before powering up, this
> is
> > +    * necessary after a host controller reset.
> > +    */
> > +   if (mode == MMC_POWER_UP) {
> > +           readl_poll_timeout(host->ioaddr + SDHCI_PRESENT_STATE, reg,
> reg & SDHCI_CD_STABLE,
> > +                              CD_STABLE_MAX_SLEEP_US,
> CD_STABLE_TIMEOUT_US);
> > +   }
>
> Doesn't need {}
Will remove in v2.

>
> Will this work with all Arasan variants?
Yes, this is expected to work across all Arasan variants that comply with the standard
SDHCI register definitions. The SDHCI_CD_STABLE bit is defined in both the
standard SDHCI specification and Arasan's user guide.
On Xilinx/AMD Versal and ZynqMP platforms, the CD stable bit is typically set within
a few milliseconds. However, to be on the safer side and ensure compatibility across
all Arasan variants, a timeout of 1 second is added.
Please let me know if you prefer to increase the timeout or if this logic should be
enabled by a platform specific quirk.

Regards
Sai Krishna

>
> > +
> > +   sdhci_set_power_and_bus_voltage(host, mode, vdd); }
> > +
> >  static const struct sdhci_ops sdhci_arasan_ops = {
> >     .set_clock = sdhci_arasan_set_clock,
> >     .get_max_clock = sdhci_pltfm_clk_get_max_clock, @@ -521,7 +541,7
> @@
> > static const struct sdhci_ops sdhci_arasan_ops = {
> >     .set_bus_width = sdhci_set_bus_width,
> >     .reset = sdhci_arasan_reset,
> >     .set_uhs_signaling = sdhci_set_uhs_signaling,
> > -   .set_power = sdhci_set_power_and_bus_voltage,
> > +   .set_power = sdhci_arasan_set_power_and_bus_voltage,
> >     .hw_reset = sdhci_arasan_hw_reset,
> >  };
> >
> > @@ -570,7 +590,7 @@ static const struct sdhci_ops sdhci_arasan_cqe_ops = {
> >     .set_bus_width = sdhci_set_bus_width,
> >     .reset = sdhci_arasan_reset,
> >     .set_uhs_signaling = sdhci_set_uhs_signaling,
> > -   .set_power = sdhci_set_power_and_bus_voltage,
> > +   .set_power = sdhci_arasan_set_power_and_bus_voltage,
> >     .irq = sdhci_arasan_cqhci_irq,
> >  };
> >