Re: [PATCH v2] mmc: inline the first mmc_scan() on mmc_start_host()

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

Hi Dennis,

On Thu, Mar 30, 2023 at 1:48 AM Dennis Zhou <dennis@xxxxxxxxxx> wrote:
> When using dm-verity with a data partition on an emmc device, dm-verity
> races with the discovery of attached emmc devices. This is because mmc's
> probing code sets up the host data structure then a work item is
> scheduled to do discovery afterwards. To prevent this race on init,
> let's inline the first call to detection, __mm_scan(), and let
> subsequent detect calls be handled via the workqueue.
>
> Signed-off-by: Dennis Zhou <dennis@xxxxxxxxxx>

Thanks for your patch, which is now commit 2cc83bf7d41113d9 ("mmc:
core: Allow mmc_start_host() synchronously detect a card") in
linux-next/master mmc/next next-20230614 next-20230615 next-20230616

I have bisected the following failure on Renesas Salvator-XS with R-Car H3
ES2.0 to the above commit:

    renesas_sdhi_internal_dmac ee140000.mmc: timeout waiting for
hardware interrupt (CMD0)
    renesas_sdhi_internal_dmac ee140000.mmc: timeout waiting for
hardware interrupt (CMD1)
    renesas_sdhi_internal_dmac ee140000.mmc: timeout waiting for
hardware interrupt (CMD0)
    renesas_sdhi_internal_dmac ee140000.mmc: timeout waiting for
hardware interrupt (CMD1)
    mmc0: Failed to initialize a non-removable card

Reverting the commit fixes the issue for me.

> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2185,10 +2185,8 @@ int mmc_card_alternative_gpt_sector(struct mmc_card *card, sector_t *gpt_sector)
>  }
>  EXPORT_SYMBOL(mmc_card_alternative_gpt_sector);
>
> -void mmc_rescan(struct work_struct *work)
> +static void __mmc_rescan(struct mmc_host *host)
>  {
> -       struct mmc_host *host =
> -               container_of(work, struct mmc_host, detect.work);
>         int i;
>
>         if (host->rescan_disable)
> @@ -2249,6 +2247,14 @@ void mmc_rescan(struct work_struct *work)
>                 mmc_schedule_delayed_work(&host->detect, HZ);
>  }
>
> +void mmc_rescan(struct work_struct *work)
> +{
> +       struct mmc_host *host =
> +               container_of(work, struct mmc_host, detect.work);
> +
> +       __mmc_rescan(host);
> +}
> +
>  void mmc_start_host(struct mmc_host *host)
>  {
>         host->f_init = max(min(freqs[0], host->f_max), host->f_min);
> @@ -2261,7 +2267,8 @@ void mmc_start_host(struct mmc_host *host)
>         }
>
>         mmc_gpiod_request_cd_irq(host);
> -       _mmc_detect_change(host, 0, false);
> +       host->detect_change = 1;
> +       __mmc_rescan(host);
>  }
>
>  void __mmc_stop_host(struct mmc_host *host)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds