Re: [PATCH] mmc: meson-gx: check for scatterlist size alignment in block mode

[Ulf Hansson <ulf.hansson@linaro.org>]

On Fri, 18 Dec 2020 at 08:54, Dmitry Lebed <lebed.dmitry@gmail.com> wrote:
>
> Enable SGDMA support for SD_IO_RW_EXTENDED and add proper check
> for scatterlist size alignment in block mode.
>
> According to documentation, in SDIO block mode meson-gx DMA could
> only handle buffers with sizes that are multiples of SDIO block size.
>
> Some SDIO drivers like brcmfmac use scatterlist API, but do not enforce
> proper scatterlist buffer size alignemnt, this looks like a root cause
> of non-working CMD53.
>
> Some minor style fixes.
>
> Signed-off-by: Dmitry Lebed <lebed.dmitry@gmail.com>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/meson-gx-mmc.c | 37 ++++++++++++++++++++-------------
>  1 file changed, 22 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index 13f6a2c0ed04..eb6c02bc4a02 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -227,7 +227,6 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
>         struct mmc_data *data = mrq->data;
>         struct scatterlist *sg;
>         int i;
> -       bool use_desc_chain_mode = true;
>
>         /*
>          * When Controller DMA cannot directly access DDR memory, disable
> @@ -237,25 +236,33 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
>         if (host->dram_access_quirk)
>                 return;
>
> -       /*
> -        * Broken SDIO with AP6255-based WiFi on Khadas VIM Pro has been
> -        * reported. For some strange reason this occurs in descriptor
> -        * chain mode only. So let's fall back to bounce buffer mode
> -        * for command SD_IO_RW_EXTENDED.
> -        */
> -       if (mrq->cmd->opcode == SD_IO_RW_EXTENDED)
> -               return;
> +       if (data->blocks > 1) {
> +               /*
> +                * In block mode DMA descriptor format, "length" field indicates
> +                * number of blocks and there is no way to pass DMA size that
> +                * is not multiple of SDIO block size, making it impossible to
> +                * tie more than one memory buffer with single SDIO block.
> +                * Block mode sg buffer size should be aligned with SDIO block
> +                * size, otherwise chain mode could not be used.
> +                */
> +               for_each_sg(data->sg, sg, data->sg_len, i) {
> +                       if (sg->length % data->blksz) {
> +                               WARN_ONCE(1, "unaligned sg len %u blksize %u\n",
> +                                         sg->length, data->blksz);
> +                               return;
> +                       }
> +               }
> +       }
>
> -       for_each_sg(data->sg, sg, data->sg_len, i)
> +       for_each_sg(data->sg, sg, data->sg_len, i) {
>                 /* check for 8 byte alignment */
> -               if (sg->offset & 7) {
> +               if (sg->offset % 8) {
>                         WARN_ONCE(1, "unaligned scatterlist buffer\n");
> -                       use_desc_chain_mode = false;
> -                       break;
> +                       return;
>                 }
> +       }
>
> -       if (use_desc_chain_mode)
> -               data->host_cookie |= SD_EMMC_DESC_CHAIN_MODE;
> +       data->host_cookie |= SD_EMMC_DESC_CHAIN_MODE;
>  }
>
>  static inline bool meson_mmc_desc_chain_mode(const struct mmc_data *data)
> --
> 2.24.3 (Apple Git-128)
>