Re: [PATCH] mmc: sdhci: Fix max_seg_size for 64KiB PAGE_SIZE

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On Wed, 10 Jul 2024 at 20:09, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> blk_queue_max_segment_size() ensured:
>
>         if (max_size < PAGE_SIZE)
>                 max_size = PAGE_SIZE;
>
> whereas:
>
> blk_validate_limits() makes it an error:
>
>         if (WARN_ON_ONCE(lim->max_segment_size < PAGE_SIZE))
>                 return -EINVAL;
>
> The change from one to the other, exposed sdhci which was setting maximum
> segment size too low in some circumstances.
>
> Fix the maximum segment size when it is too low.
>
> Fixes: 616f87661792 ("mmc: pass queue_limits to blk_mq_alloc_disk")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>

Applied for fixes, thanks!

If we want to log a message due to the wrong max_seg_size, let's do
that from a patch on top.

Kind regards
Uffe


> ---
>  drivers/mmc/host/sdhci.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index a20df9383b20..4b91c9e96635 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -4708,6 +4708,21 @@ int sdhci_setup_host(struct sdhci_host *host)
>                 if (host->quirks & SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC) {
>                         host->max_adma = 65532; /* 32-bit alignment */
>                         mmc->max_seg_size = 65535;
> +                       /*
> +                        * sdhci_adma_table_pre() expects to define 1 DMA
> +                        * descriptor per segment, so the maximum segment size
> +                        * is set accordingly. SDHCI allows up to 64KiB per DMA
> +                        * descriptor (16-bit field), but some controllers do
> +                        * not support "zero means 65536" reducing the maximum
> +                        * for them to 65535. That is a problem if PAGE_SIZE is
> +                        * 64KiB because the block layer does not support
> +                        * max_seg_size < PAGE_SIZE, however
> +                        * sdhci_adma_table_pre() has a workaround to handle
> +                        * that case, and split the descriptor. Refer also
> +                        * comment in sdhci_adma_table_pre().
> +                        */
> +                       if (mmc->max_seg_size < PAGE_SIZE)
> +                               mmc->max_seg_size = PAGE_SIZE;
>                 } else {
>                         mmc->max_seg_size = 65536;
>                 }
> --
> 2.34.1
>




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