linux-kernel - Re: [PATCH] mmc: mtk-sd: reduce CIT for better performance

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Date:   Tue, 9 May 2023 11:29:11 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Wenbin Mei <wenbin.mei@...iatek.com>
Cc:     Chaotian Jing <chaotian.jing@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] mmc: mtk-sd: reduce CIT for better performance

On Wed, 19 Apr 2023 at 08:30, Wenbin Mei <wenbin.mei@...iatek.com> wrote:
>
> CQHCI_SSC1 indicates to CQE the polling period to use when using
> periodic SEND_QUEUE_STATUS(CMD13) polling.
> The default value is 0x1000, now change it to 0x40, which can
> improve the performance of some eMMC devices.

Rather than just providing hexadecimal numbers, would you mind
explaining a bit what it translates into?

For example, "the default value 0x1000 that corresponds to x ms...,
... lets' decrease it to 0x40 that corresponds to x ms".

Moreover, it would be nice to have a comment in the code too,
explaining what 0x40 translates into.

Other than this, this looks good to me.

Kind regards
Uffe

>
> Signed-off-by: Wenbin Mei <wenbin.mei@...iatek.com>
> ---
>  drivers/mmc/host/mtk-sd.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> index edade0e54a0c..483353ea3a99 100644
> --- a/drivers/mmc/host/mtk-sd.c
> +++ b/drivers/mmc/host/mtk-sd.c
> @@ -2453,6 +2453,7 @@ static void msdc_hs400_enhanced_strobe(struct mmc_host *mmc,
>  static void msdc_cqe_enable(struct mmc_host *mmc)
>  {
>         struct msdc_host *host = mmc_priv(mmc);
> +       struct cqhci_host *cq_host = mmc->cqe_private;
>
>         /* enable cmdq irq */
>         writel(MSDC_INT_CMDQ, host->base + MSDC_INTEN);
> @@ -2462,6 +2463,8 @@ static void msdc_cqe_enable(struct mmc_host *mmc)
>         msdc_set_busy_timeout(host, 20 * 1000000000ULL, 0);
>         /* default read data timeout 1s */
>         msdc_set_timeout(host, 1000000000ULL, 0);
> +
> +       cqhci_writel(cq_host, 0x40, CQHCI_SSC1);
>  }
>
>  static void msdc_cqe_disable(struct mmc_host *mmc, bool recovery)
> --
> 2.25.1
>