linux-kernel - Re: [RFC PATCH 2/2] mmc: Allow tuning to be skipped during card init

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Message-ID: <CAPDyKForwTcjEaP4n56zw_VsvmZ=cZZ5BgauL1v_-MnP4En=TQ@mail.gmail.com>
Date: Mon, 3 Feb 2025 14:49:17 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Erick Shepherd <erick.shepherd@...com>
Cc: linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org, york.yang@....com
Subject: Re: [RFC PATCH 2/2] mmc: Allow tuning to be skipped during card init

On Mon, 27 Jan 2025 at 23:41, Erick Shepherd <erick.shepherd@...com> wrote:
>
> Add a new field to the mmc_host struct to track when the card should
> skip the initial tuning and use it to conditionally stop tuning in the
> mmc_sd_init_uhs_card function. Currently the new field only gets set
> when a DDR50 card fails to tune, which indicates the card does not
> support tuning.
>
> Signed-off-by: Erick Shepherd <erick.shepherd@...com>
> ---
>  drivers/mmc/core/sd.c    | 4 +++-
>  include/linux/mmc/host.h | 1 +
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index cc757b850e79..353715fd8f53 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -663,7 +663,8 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
>         if (!mmc_host_is_spi(card->host) &&
>                 (card->host->ios.timing == MMC_TIMING_UHS_SDR50 ||
>                  card->host->ios.timing == MMC_TIMING_UHS_DDR50 ||
> -                card->host->ios.timing == MMC_TIMING_UHS_SDR104)) {
> +                card->host->ios.timing == MMC_TIMING_UHS_SDR104) &&
> +               !card->host->skip_init_tune) {
>                 err = mmc_execute_tuning(card);
>
>                 /*
> @@ -676,6 +677,7 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
>                 if (err && card->host->ios.timing == MMC_TIMING_UHS_DDR50) {
>                         pr_warn("%s: ddr50 tuning failed\n",
>                                 mmc_hostname(card->host));
> +                       card->host->skip_init_tune = 1;

Rather than adding a host specific flag to let the core signal to the
host driver that it should skip tuning, I think it would be better if
we can avoid the core to request a tuning instead.

So we need to get the information from the host, during the first
tuning attempt if it fails and then the tuning should be disabled for
the *card*, forever.

>                         err = 0;
>                 }
>         }
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 68f09a955a90..91c4db6837c9 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -486,6 +486,7 @@ struct mmc_host {
>         unsigned int            use_spi_crc:1;
>         unsigned int            claimed:1;      /* host exclusively claimed */
>         unsigned int            doing_init_tune:1; /* initial tuning in progress */
> +       unsigned int            skip_init_tune:1;       /* skip the initial tuning */
>         unsigned int            can_retune:1;   /* re-tuning can be used */
>         unsigned int            doing_retune:1; /* re-tuning in progress */
>         unsigned int            retune_now:1;   /* do re-tuning at next req */
> --
> 2.43.0
>

Again, please re-submit and loop in Adrian to get his opinion on this.

Kind regards
Uffe