Re: [PATCH] mmc: meson-gx: limit segments to 1 when dram-access-quirk is needed

From: Ulf Hansson <ulf.hansson@linaro.org>
To: Neil Armstrong <narmstrong@baylibre.com>
Cc: "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
	Christian Hewitt <christianshewitt@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"open list:ARM/Amlogic Meson..."
	<linux-amlogic@lists.infradead.org>, Art Nikpal <art@khadas.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] mmc: meson-gx: limit segments to 1 when dram-access-quirk is needed
Date: Tue, 16 Jun 2020 13:32:36 +0200	[thread overview]
Message-ID: <CAPDyKFo7VA-wbOZUxExUpPoc+u446KecFARX0KNCakaubowpXg@mail.gmail.com> (raw)
In-Reply-To: <20200608084458.32014-1-narmstrong@baylibre.com>

On Mon, 8 Jun 2020 at 10:45, Neil Armstrong <narmstrong@baylibre.com> wrote:
>
> The actual max_segs computation leads to failure while using the broadcom
> sdio brcmfmac/bcmsdh driver, since the driver tries to make usage of scatter
> gather.
>
> But with the dram-access-quirk we use a 1,5K SRAM bounce buffer, and the
> max_segs current value of 3 leads to max transfers to 4,5k, which doesn't work.
>
> This patch sets max_segs to 1 to better describe the hardware limitation,
> and fix the SDIO functionnality with the brcmfmac/bcmsdh driver on Amlogic
> G12A/G12B SoCs on boards like SEI510 or Khadas VIM3.
>
> Reported-by: Art Nikpal <art@khadas.com>
> Reported-by: Christian Hewitt <christianshewitt@gmail.com>
> Fixes: acdc8e71d9bb ("mmc: meson-gx: add dram-access-quirk")
> 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 | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index 35400cf2a2e4..cfaf8e7e22ec 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -1143,9 +1143,11 @@ static int meson_mmc_probe(struct platform_device *pdev)
>
>         mmc->caps |= MMC_CAP_CMD23;
>         if (host->dram_access_quirk) {
> +               /* Limit segments to 1 due to low available sram memory */
> +               mmc->max_segs = 1;
>                 /* Limit to the available sram memory */
> -               mmc->max_segs = SD_EMMC_SRAM_DATA_BUF_LEN / mmc->max_blk_size;
> -               mmc->max_blk_count = mmc->max_segs;
> +               mmc->max_blk_count = SD_EMMC_SRAM_DATA_BUF_LEN /
> +                                    mmc->max_blk_size;
>         } else {
>                 mmc->max_blk_count = CMD_CFG_LENGTH_MASK;
>                 mmc->max_segs = SD_EMMC_DESC_BUF_LEN /
> --
> 2.22.0
>

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