Re: [PATCH v4] mmc: host: sdhci-sprd: Fix the incorrect soft reset operation when runtime resuming

[Ulf Hansson]

On Wed, 17 Jul 2019 at 04:29, Baolin Wang <baolin.wang@xxxxxxxxxx> wrote:
>
> In sdhci_runtime_resume_host() function, we will always do software reset
> for all, which will cause Spreadtrum host controller work abnormally after
> resuming.

What does "software reset for all" means?

>
> Thus for Spreadtrum platform that will not power down the SD/eMMC card during
> runtime suspend, we should not do software reset for all.

Normally, sdhci hosts that enters runtime suspend doesn't power off
the card (there are some exceptions like PCI variants).

So, what's so special here and how does the reset come into play? I
don't see sdhci doing a reset in sdhci_runtime_suspend|resume_host()
and nor doesn the callback from the sdhci-sprd.c variant doing it.

> To fix this
> issue, adding a specific reset operation that adds one condition to validate
> the power mode to decide if we can do software reset for all or just reset
> command and data lines.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
> ---
> Changess from v3:
>  - Use ios.power_mode to validate if the card is power down or not.
>
> Changes from v2:
>  - Simplify the sdhci_sprd_reset() by issuing sdhci_reset().
>
> Changes from v1:
>  - Add a specific reset operation instead of changing the core to avoid
>  affecting other hardware.
> ---
>  drivers/mmc/host/sdhci-sprd.c |   19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-sprd.c b/drivers/mmc/host/sdhci-sprd.c
> index 603a5d9..94f9726 100644
> --- a/drivers/mmc/host/sdhci-sprd.c
> +++ b/drivers/mmc/host/sdhci-sprd.c
> @@ -373,6 +373,23 @@ static unsigned int sdhci_sprd_get_max_timeout_count(struct sdhci_host *host)
>         return 1 << 31;
>  }
>
> +static void sdhci_sprd_reset(struct sdhci_host *host, u8 mask)
> +{
> +       struct mmc_host *mmc = host->mmc;
> +
> +       /*
> +        * When try to reset controller after runtime suspend, we should not
> +        * reset for all if the SD/eMMC card is not power down, just reset
> +        * command and data lines instead. Otherwise will meet some strange
> +        * behaviors for Spreadtrum host controller.
> +        */
> +       if (host->runtime_suspended && (mask & SDHCI_RESET_ALL) &&
> +           mmc->ios.power_mode == MMC_POWER_ON)
> +               mask = SDHCI_RESET_CMD | SDHCI_RESET_DATA;

Can sdhci_sprd_reset() be called when the host is runtime suspended?
That sounds like a bug to me, no?

> +
> +       sdhci_reset(host, mask);
> +}
> +
>  static struct sdhci_ops sdhci_sprd_ops = {
>         .read_l = sdhci_sprd_readl,
>         .write_l = sdhci_sprd_writel,
> @@ -381,7 +398,7 @@ static unsigned int sdhci_sprd_get_max_timeout_count(struct sdhci_host *host)
>         .get_max_clock = sdhci_sprd_get_max_clock,
>         .get_min_clock = sdhci_sprd_get_min_clock,
>         .set_bus_width = sdhci_set_bus_width,
> -       .reset = sdhci_reset,
> +       .reset = sdhci_sprd_reset,
>         .set_uhs_signaling = sdhci_sprd_set_uhs_signaling,
>         .hw_reset = sdhci_sprd_hw_reset,
>         .get_max_timeout_count = sdhci_sprd_get_max_timeout_count,
> --
> 1.7.9.5
>

Kind regards
Uffe