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References: <20210809072315.1127-1-derong.liu@mediatek.com>
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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Mon, 16 Aug 2021 12:27:04 +0200
Message-ID: <CAPDyKFq3_eia7cvo-1Ajj5wcrfEHtp_EsMp27uL4dC_n+vPWZQ@mail.gmail.com>
Subject: Re: [PATCH v2] mmc: mediatek: add wait dma stop done flow
To:     Derong Liu <derong.liu@mediatek.com>
Cc:     Chaotian Jing <chaotian.jing@mediatek.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        linux-mmc <linux-mmc@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        wsp_upstream@mediatek.com, Peng Zhou <peng.zhou@mediatek.com>
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On Mon, 9 Aug 2021 at 09:25, Derong Liu <derong.liu@mediatek.com> wrote:
>
> We found this issue on a 5G platform, during CMDQ error handling, if DMA status is active when it call msdc_reset_hw, it means mmc host hw reset and DMA transfer will be parallel, mmc host may access sram region unexpectedly.
>
> According to the programming guide of mtk mmc host,it needs to wait for dma stop done after set dma stop.
> This change should be applied to all SoCs.
>
> Signed-off-by: Derong Liu <derong.liu@mediatek.com>
> ---
>  drivers/mmc/host/mtk-sd.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> index 4dfc246c5f95..1dfd2842471b 100644
> --- a/drivers/mmc/host/mtk-sd.c
> +++ b/drivers/mmc/host/mtk-sd.c
> @@ -2339,6 +2339,8 @@ static void msdc_cqe_disable(struct mmc_host *mmc, bool recovery)
>         if (recovery) {
>                 sdr_set_field(host->base + MSDC_DMA_CTRL,
>                               MSDC_DMA_CTRL_STOP, 1);
> +               while (readl(host->base + MSDC_DMA_CFG) & MSDC_DMA_CFG_STS)
> +                       cpu_relax();

I suggest you look into using readl_poll_timeout() - as we don't want
to hang indefinitely, no matter what.

>                 msdc_reset_hw(host);
>         }
>  }
> --
> 2.18.0

Kind regards
Uffe