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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Tue, 11 May 2021 12:56:17 +0200
Message-ID: <CAPDyKFrZY0vdQrFfAGCRW2MM25WY1rivwiPv8u3aHsfwNPbe-g@mail.gmail.com>
Subject: Re: [PATCH 2/2] mmc: meson-gx: also check SD_IO_RW_EXTENDED for
 scatterlist size alignment
To:     Neil Armstrong <narmstrong@baylibre.com>
Cc:     Kevin Hilman <khilman@baylibre.com>,
        linux-mmc <linux-mmc@vger.kernel.org>,
        "open list:ARM/Amlogic Meson..." <linux-amlogic@lists.infradead.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Christian Hewitt <christianshewitt@gmail.com>
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On Mon, 26 Apr 2021 at 19:56, Neil Armstrong <narmstrong@baylibre.com> wrote:
>
> The brcmfmac driver can generate a scatterlist from a skb with each packets
> not aligned to the block size. This is not supported by the Amlogic Descriptor
> dma engine where each descriptor must match a multiple of the block size.
>
> The sg list is valid, since the sum of the sg buffers is a multiple of the
> block size, but we must discard those when in SD_IO_RW_EXTENDED mode since
> SDIO block mode can be used under the hood even with data->blocks == 1.
>
> Those transfers are very rare, thus can be replaced by a bounce buffer
> without real performance loss.
>
> Fixes: 7412dee9f1fd ("mmc: meson-gx: replace WARN_ONCE with dev_warn_once about scatterlist size alignment in block mode")
> Reported-by: Christian Hewitt <christianshewitt@gmail.com>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

Applied for fixes and by adding a stable tag, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/meson-gx-mmc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index 1c61f0f24c09..016a6106151a 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -236,7 +236,8 @@ static void meson_mmc_get_transfer_mode(struct mmc_host *mmc,
>         if (host->dram_access_quirk)
>                 return;
>
> -       if (data->blocks > 1) {
> +       /* SD_IO_RW_EXTENDED (CMD53) can also use block mode under the hood */
> +       if (data->blocks > 1 || mrq->cmd->opcode == SD_IO_RW_EXTENDED) {
>                 /*
>                  * In block mode DMA descriptor format, "length" field indicates
>                  * number of blocks and there is no way to pass DMA size that
> --
> 2.25.1
>