linux-kernel - Re: [PATCH] mmc: mediatek: wait dma stop bit reset to 0

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Message-ID: <CAPDyKFruh_t3uR3-u-_wH9LmZo77Ra-LumKe808jDfbGGM+04Q@mail.gmail.com>
Date:   Tue, 7 Jun 2022 12:35:53 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Mengqi Zhang <mengqi.zhang@...iatek.com>
Cc:     chaotian.jing@...iatek.com, matthias.bgg@...il.com,
        linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: mediatek: wait dma stop bit reset to 0

On Mon, 6 Jun 2022 at 16:21, Mengqi Zhang <mengqi.zhang@...iatek.com> wrote:
>
> MediaTek IP requires that after dma stop, it need to wait this dma stop
> bit auto-reset to 0. When bus is in high loading state, it will take a
> while for the dma stop complete. If there is no waiting operation here,
> when program runs to clear fifo and reset, bus will hang.
>
> In addition, there should be no return in msdc_data_xfer_next, because no
> matter what error occurs here, it should continue to excute to the
> following mmc_request_done. Otherwise the core layer may wait complete
> forever.
>
> Signed-off-by: Mengqi Zhang <mengqi.zhang@...iatek.com>

Is there a certain commit this fixes? In that case, we should add a fixes tag.

> ---
>  drivers/mmc/host/mtk-sd.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> index 195dc897188b..c925f45786c2 100644
> --- a/drivers/mmc/host/mtk-sd.c
> +++ b/drivers/mmc/host/mtk-sd.c
> @@ -1385,12 +1385,15 @@ static bool msdc_data_xfer_done(struct msdc_host *host, u32 events,
>                 sdr_set_field(host->base + MSDC_DMA_CTRL, MSDC_DMA_CTRL_STOP,
>                                 1);
>
> +               ret = readl_poll_timeout_atomic(host->base + MSDC_DMA_CTRL, val,
> +                                               !(val & MSDC_DMA_CTRL_STOP), 1, 20000);
> +               if (ret)
> +                       dev_dbg(host->dev, "DMA stop timed out\n");
> +
>                 ret = readl_poll_timeout_atomic(host->base + MSDC_DMA_CFG, val,
>                                                 !(val & MSDC_DMA_CFG_STS), 1, 20000);
> -               if (ret) {
> -                       dev_dbg(host->dev, "DMA stop timed out\n");
> -                       return false;

Looks like msdc_data_xfer_done() should be turned into a void
function, as it would always return true beyond this change.

> -               }
> +               if (ret)
> +                       dev_dbg(host->dev, "DMA inactive timed out\n");
>
>                 sdr_clr_bits(host->base + MSDC_INTEN, data_ints_mask);
>                 dev_dbg(host->dev, "DMA stop\n");
> @@ -2416,6 +2419,9 @@ 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);
> +               if (WARN_ON(readl_poll_timeout(host->base + MSDC_DMA_CTRL, val,
> +                       !(val & MSDC_DMA_CTRL_STOP), 1, 3000)))
> +                       return;
>                 if (WARN_ON(readl_poll_timeout(host->base + MSDC_DMA_CFG, val,
>                         !(val & MSDC_DMA_CFG_STS), 1, 3000)))
>                         return;

Kind regards
Uffe