[PATCH] spi: atmel: Prevent spi transfers from being killed

[Ronald Wahl]

On 05.12.23 09:31, Miquel Raynal wrote:
> Upstream commit e0205d6203c2 ("spi: atmel: Prevent false timeouts on
> long transfers") has tried to mitigate the problem of getting spi
> transfers canceled because they were lasting too long. On slow buses,
> transfers in the MiB range can take more than one second and thus a
> calculation was added to progressively increment the timeout value. In
> order to not be too problematic from a user point of view (waiting dozen
> of seconds or even minutes), the wait call was turned interruptible.
>
> Turning the wait interruptible was a mistake as what we really wanted to
> do was to be able to kill a transfer. Any signal interrupting our
> transfer would not be suitable at all so a second attempt was made at
> turning the wait killable instead.
>
> Link: https://lore.kernel.org/linux-spi/20231127095842.389631-1-miquel.raynal@bootlin.com/
>
> All being well, it was reported that JFFS2 was showing a splat when
> interrupting a transfer. After some more debate about whether JFFS2
> should be fixed and how, it was also pointed out that the whole
> consistency of the filesystem in case of parallel I/O would be
> compromised. Changing JFFS2 behavior would in theory be possible but
> nobody has the energy and time and knowledge to do this now, so better
> prevent spi transfers to be interrupted by the user.
>
> Partially revert the blamed commit to no longer use the interruptible
> nor the killable variant of wait_for_completion().
>
> Fixes: e0205d6203c2 ("spi: atmel: Prevent false timeouts on long transfers")
> Cc: stable at vger.kernel.org

Tested-by: Ronald Wahl <ronald.wahl at raritan.com>

> Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
> ---
>   drivers/spi/spi-atmel.c | 10 ++++------
>   1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
> index 0197c25f5029..54277de30161 100644
> --- a/drivers/spi/spi-atmel.c
> +++ b/drivers/spi/spi-atmel.c
> @@ -1333,12 +1333,10 @@ static int atmel_spi_one_transfer(struct spi_controller *host,
>               }
>
>               dma_timeout = msecs_to_jiffies(spi_controller_xfer_timeout(host, xfer));
> -             ret_timeout = wait_for_completion_killable_timeout(&as->xfer_completion,
> -                                                                dma_timeout);
> -             if (ret_timeout <= 0) {
> -                     dev_err(&spi->dev, "spi transfer %s\n",
> -                             !ret_timeout ? "timeout" : "canceled");
> -                     as->done_status = ret_timeout < 0 ? ret_timeout : -EIO;
> +             ret_timeout = wait_for_completion_timeout(&as->xfer_completion, dma_timeout);
> +             if (!ret_timeout) {
> +                     dev_err(&spi->dev, "spi transfer timeout\n");
> +                     as->done_status = -EIO;
>               }
>
>               if (as->done_status)


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