linux-kernel - Re: [PATCHv5] mmc: block: Check for errors after write on SPI

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Date:   Mon, 28 Mar 2022 16:05:01 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Christian Löhle <CLoehle@...erstone.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCHv5] mmc: block: Check for errors after write on SPI

On Thu, 24 Mar 2022 at 15:18, Christian Löhle <CLoehle@...erstone.com> wrote:
>
> Introduce a SEND_STATUS check for writes through SPI to not mark
> an unsuccessful write as successful.
>
> Since SPI SD/MMC does not have states, after a write, the card will
> just hold the line LOW until it is ready again. The driver marks the
> write therefore as completed as soon as it reads something other than
> all zeroes.
> The driver does not distinguish from a card no longer signalling busy
> and it being disconnected (and the line being pulled-up by the host).
> This lead to writes being marked as successful when disconnecting
> a busy card.
> Now the card is ensured to be still connected by an additional CMD13,
> just like non-SPI is ensured to go back to TRAN state.
>
> While at it and since we already poll for the post-write status anyway,
> we might as well check for SPIs error bits (any of them).
>
> The disconnecting card problem is reproducable for me after continuous
> write activity and randomly disconnecting, around every 20-50 tries
> on SPI DS for some card.
>
> Fixes: 7213d175e3b6f ("MMC/SD card driver learns SPI")
> Cc: stable@...r.kernel.org
> Signed-off-by: Christian Loehle <cloehle@...erstone.com>

Applied for fixes, thanks!

Kind regards
Uffe


> ---
> v2:
>   - Reorder err and status check for err to take precedence and look cleaner
> v3:
>   - Move the logic into its own function
> v4:
>   - Move block layer handling out of the spi-specific function
> v5:
>   - reorder err and status check
>
>  drivers/mmc/core/block.c | 34 +++++++++++++++++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 4e67c1403cc9..be2078684417 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -1880,6 +1880,31 @@ static inline bool mmc_blk_rq_error(struct mmc_blk_request *brq)
>                brq->data.error || brq->cmd.resp[0] & CMD_ERRORS;
>  }
>
> +static int mmc_spi_err_check(struct mmc_card *card)
> +{
> +       u32 status = 0;
> +       int err;
> +
> +       /*
> +        * SPI does not have a TRAN state we have to wait on, instead the
> +        * card is ready again when it no longer holds the line LOW.
> +        * We still have to ensure two things here before we know the write
> +        * was successful:
> +        * 1. The card has not disconnected during busy and we actually read our
> +        * own pull-up, thinking it was still connected, so ensure it
> +        * still responds.
> +        * 2. Check for any error bits, in particular R1_SPI_IDLE to catch a
> +        * just reconnected card after being disconnected during busy.
> +        */
> +       err = __mmc_send_status(card, &status, 0);
> +       if (err)
> +               return err;
> +       /* All R1 and R2 bits of SPI are errors in our case */
> +       if (status)
> +               return -EIO;
> +       return 0;
> +}
> +
>  static int mmc_blk_busy_cb(void *cb_data, bool *busy)
>  {
>         struct mmc_blk_busy_data *data = cb_data;
> @@ -1903,9 +1928,16 @@ static int mmc_blk_card_busy(struct mmc_card *card, struct request *req)
>         struct mmc_blk_busy_data cb_data;
>         int err;
>
> -       if (mmc_host_is_spi(card->host) || rq_data_dir(req) == READ)
> +       if (rq_data_dir(req) == READ)
>                 return 0;
>
> +       if (mmc_host_is_spi(card->host)) {
> +               err = mmc_spi_err_check(card);
> +               if (err)
> +                       mqrq->brq.data.bytes_xfered = 0;
> +               return err;
> +       }
> +
>         cb_data.card = card;
>         cb_data.status = 0;
>         err = __mmc_poll_for_busy(card->host, 0, MMC_BLK_TIMEOUT_MS,
> --
> 2.34.1
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