Re: [PATCH v3] mmc: core: Set HS clock speed before sending HS CMD13

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

On Wed, 30 Mar 2022 at 22:30, Brian Norris <briannorris@chromium.org> wrote:
>
> Way back in commit 4f25580fb84d ("mmc: core: changes frequency to
> hs_max_dtr when selecting hs400es"), Rockchip engineers noticed that
> some eMMC don't respond to SEND_STATUS commands very reliably if they're
> still running at a low initial frequency. As mentioned in that commit,
> JESD84-B51 P49 suggests a sequence in which the host:
> 1. sets HS_TIMING
> 2. bumps the clock ("<= 52 MHz")
> 3. sends further commands
>
> It doesn't exactly require that we don't use a lower-than-52MHz
> frequency, but in practice, these eMMC don't like it.
>
> The aforementioned commit tried to get that right for HS400ES, although
> it's unclear whether this ever truly worked as committed into mainline,
> as other changes/refactoring adjusted the sequence in conflicting ways:
>
> 08573eaf1a70 ("mmc: mmc: do not use CMD13 to get status after speed mode
> switch")
>
> 53e60650f74e ("mmc: core: Allow CMD13 polling when switching to HS mode
> for mmc")
>
> In any case, today we do step 3 before step 2. Let's fix that, and also
> apply the same logic to HS200/400, where this eMMC has problems too.
>
> Resolves errors like this seen when booting some RK3399 Gru/Scarlet
> systems:
>
> [    2.058881] mmc1: CQHCI version 5.10
> [    2.097545] mmc1: SDHCI controller on fe330000.mmc [fe330000.mmc] using ADMA
> [    2.209804] mmc1: mmc_select_hs400es failed, error -84
> [    2.215597] mmc1: error -84 whilst initialising MMC card
> [    2.417514] mmc1: mmc_select_hs400es failed, error -110
> [    2.423373] mmc1: error -110 whilst initialising MMC card
> [    2.605052] mmc1: mmc_select_hs400es failed, error -110
> [    2.617944] mmc1: error -110 whilst initialising MMC card
> [    2.835884] mmc1: mmc_select_hs400es failed, error -110
> [    2.841751] mmc1: error -110 whilst initialising MMC card
>
> Fixes: 08573eaf1a70 ("mmc: mmc: do not use CMD13 to get status after speed mode switch")
> Fixes: 53e60650f74e ("mmc: core: Allow CMD13 polling when switching to HS mode for mmc")
> Fixes: 4f25580fb84d ("mmc: core: changes frequency to hs_max_dtr when selecting hs400es")
> Cc: Shawn Lin <shawn.lin@rock-chips.com>
> Signed-off-by: Brian Norris <briannorris@chromium.org>

To get this thoroughly tested, I have applied it to my next branch, for now.

If it turns out that there are no regressions being reported, I think
we should move the patch to the fixes branch (to get it included for
v5.18) and then also tag it for stable. So, I will get back to this in
a couple of weeks.

Thanks and kind regards
Uffe


> ---
>
> Changes in v3:
>  * Use mmc_set_bus_speed() to help choose the right clock rate
>  * Avoid redundant clock rate changes
>  * Restore clock rate on failed HS200 switch
>
> Changes in v2:
>  * Use ext_csd.hs200_max_dtr for HS200
>  * Retest on top of 3b6c472822f8 ("mmc: core: Improve fallback to speed
>    modes if eMMC HS200 fails")
>
>  drivers/mmc/core/core.c |  3 +++
>  drivers/mmc/core/mmc.c  | 21 +++++++++++++++++----
>  2 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 368f10405e13..61abae221623 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -914,6 +914,9 @@ void mmc_set_clock(struct mmc_host *host, unsigned int hz)
>         if (hz > host->f_max)
>                 hz = host->f_max;
>
> +       if (host->ios.clock == hz)
> +               return;
> +
>         host->ios.clock = hz;
>         mmc_set_ios(host);
>  }
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index e7ea45386c22..1f22f1d2e9b8 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1384,13 +1384,17 @@ static int mmc_select_hs400es(struct mmc_card *card)
>                 goto out_err;
>         }
>
> +       /*
> +        * Bump to HS timing and frequency. Some cards don't handle
> +        * SEND_STATUS reliably at the initial frequency.
> +        */
>         mmc_set_timing(host, MMC_TIMING_MMC_HS);
> +       mmc_set_bus_speed(card);
> +
>         err = mmc_switch_status(card, true);
>         if (err)
>                 goto out_err;
>
> -       mmc_set_clock(host, card->ext_csd.hs_max_dtr);
> -
>         /* Switch card to DDR with strobe bit */
>         val = EXT_CSD_DDR_BUS_WIDTH_8 | EXT_CSD_BUS_WIDTH_STROBE;
>         err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> @@ -1448,7 +1452,7 @@ static int mmc_select_hs400es(struct mmc_card *card)
>  static int mmc_select_hs200(struct mmc_card *card)
>  {
>         struct mmc_host *host = card->host;
> -       unsigned int old_timing, old_signal_voltage;
> +       unsigned int old_timing, old_signal_voltage, old_clock;
>         int err = -EINVAL;
>         u8 val;
>
> @@ -1479,8 +1483,15 @@ static int mmc_select_hs200(struct mmc_card *card)
>                                    false, true, MMC_CMD_RETRIES);
>                 if (err)
>                         goto err;
> +
> +               /*
> +                * Bump to HS200 timing and frequency. Some cards don't
> +                * handle SEND_STATUS reliably at the initial frequency.
> +                */
>                 old_timing = host->ios.timing;
> +               old_clock = host->ios.clock;
>                 mmc_set_timing(host, MMC_TIMING_MMC_HS200);
> +               mmc_set_bus_speed(card);
>
>                 /*
>                  * For HS200, CRC errors are not a reliable way to know the
> @@ -1493,8 +1504,10 @@ static int mmc_select_hs200(struct mmc_card *card)
>                  * mmc_select_timing() assumes timing has not changed if
>                  * it is a switch error.
>                  */
> -               if (err == -EBADMSG)
> +               if (err == -EBADMSG) {
> +                       mmc_set_clock(host, old_clock);
>                         mmc_set_timing(host, old_timing);
> +               }
>         }
>  err:
>         if (err) {
> --
> 2.35.1.1094.g7c7d902a7c-goog
>