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

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Mar 24, 2022 at 02:18:41PM +0000, Christian Löhle 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.

LGTM, FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Fixes: 7213d175e3b6f ("MMC/SD card driver learns SPI")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christian Loehle <cloehle@hyperstone.com>
> ---
> 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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-- 
With Best Regards,
Andy Shevchenko