Re: [PATCH 3/3] mmc: sdhci: Disable re-tuning for HS400

[Ulf Hansson <ulf.hansson@linaro.org>]

On 1 December 2014 at 14:16, Adrian Hunter <adrian.hunter@intel.com> wrote:
> Re-tuning for HS400 mode must be done in HS200
> mode. Currently there is no support for that.
> That needs to be reflected in the code.
> Specifically, if tuning is executed in HS400 mode
> then return an error, and if the re-tuning timer
> is running when switching to HS400 mode, then
> disable the timer.
>
> Note that periodic re-tuning is not expected
> to be needed for HS400 but re-tuning is still
> needed after the host controller has lost power.

Why can't the old values be restored instead of trigger a re-tuning?

> In the case of suspend/resume that is not necessary
> because the card is fully re-initialised. That
> just leaves runtime suspend/resume with no support
> for HS400 re-tuning.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  drivers/mmc/host/sdhci.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 2efa7fe..a7c9e67 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1476,8 +1476,18 @@ void sdhci_set_uhs_signaling(struct sdhci_host *host, unsigned timing)
>         else if ((timing == MMC_TIMING_UHS_DDR50) ||
>                  (timing == MMC_TIMING_MMC_DDR52))
>                 ctrl_2 |= SDHCI_CTRL_UHS_DDR50;
> -       else if (timing == MMC_TIMING_MMC_HS400)
> +       else if (timing == MMC_TIMING_MMC_HS400) {
>                 ctrl_2 |= SDHCI_CTRL_HS400; /* Non-standard */
> +               /*
> +                * Periodic re-tuning for HS400 is not expected to be needed, so
> +                * disable it here.

Urgh, I don't like that the periodic tuning is handled by the host. We
should never had merged that.

How about trying to move the periodic tuning to be handled by the mmc
core instead?

> +                */
> +               if (host->flags & SDHCI_USING_RETUNING_TIMER) {
> +                       host->flags &= ~SDHCI_USING_RETUNING_TIMER;
> +                       del_timer_sync(&host->tuning_timer);
> +                       host->flags &= ~SDHCI_NEEDS_RETUNING;
> +               }
> +       }
>         sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
>  }
>  EXPORT_SYMBOL_GPL(sdhci_set_uhs_signaling);
> @@ -1897,7 +1907,11 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
>          * tuning function has to be executed.
>          */
>         switch (host->timing) {
> +       /* HS400 tuning is done in HS200 mode */
>         case MMC_TIMING_MMC_HS400:
> +               err = -EINVAL;
> +               goto out_unlock;
> +
>         case MMC_TIMING_MMC_HS200:
>         case MMC_TIMING_UHS_SDR104:
>                 break;
> --
> 1.9.1
>

Kind regards
Uffe