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Date:   Tue, 6 Jun 2023 11:58:57 +0300
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Subject: Re: [PATCH v4] mmc: mtk-sd: reduce CIT for better performance
Content-Language: en-US
To:     Wenbin Mei <wenbin.mei@mediatek.com>,
        Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Chaotian Jing <chaotian.jing@mediatek.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Ritesh Harjani <riteshh@codeaurora.org>,
        Asutosh Das <asutoshd@codeaurora.org>,
        linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org
References: <20230605121442.23622-1-wenbin.mei@mediatek.com>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
In-Reply-To: <20230605121442.23622-1-wenbin.mei@mediatek.com>
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On 5/06/23 15:14, Wenbin Mei wrote:
> CQHCI_SSC1 indicates to CQE the polling period to use when using periodic
> SEND_QUEUE_STATUS(CMD13) polling.
> Since MSDC CQE uses msdc_hclk as ITCFVAL, so driver should use hclk
> frequency to get the actual time.
> The default value 0x1000 that corresponds to 150us for MediaTek SoCs, let's
> decrease it to 0x40 that corresponds to 2.35us, which can improve the
> performance of some eMMC devices.
> 
> Signed-off-by: Wenbin Mei <wenbin.mei@mediatek.com>
> ---
>  drivers/mmc/host/cqhci.h  |  1 +
>  drivers/mmc/host/mtk-sd.c | 45 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/drivers/mmc/host/cqhci.h b/drivers/mmc/host/cqhci.h
> index ba9387ed90eb..292b89ebd978 100644
> --- a/drivers/mmc/host/cqhci.h
> +++ b/drivers/mmc/host/cqhci.h
> @@ -23,6 +23,7 @@
>  /* capabilities */
>  #define CQHCI_CAP			0x04
>  #define CQHCI_CAP_CS			0x10000000 /* Crypto Support */
> +#define CQHCI_CAP_ITCFMUL(x)		(((x) & GENMASK(15, 12)) >> 12)

Let's not open code FIELD_GET, perhaps

#define CQHCI_CAP_ITCFMUL		GENMASK(15, 12)

#define CQHCI_ITCFMUL(x)		FIELD_GET(CQHCI_CAP_ITCFMUL,(x))

>  
>  /* configuration */
>  #define CQHCI_CFG			0x08
> diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> index edade0e54a0c..9f540973caff 100644
> --- a/drivers/mmc/host/mtk-sd.c
> +++ b/drivers/mmc/host/mtk-sd.c
> @@ -473,6 +473,7 @@ struct msdc_host {
>  	struct msdc_tune_para def_tune_para; /* default tune setting */
>  	struct msdc_tune_para saved_tune_para; /* tune result of CMD21/CMD19 */
>  	struct cqhci_host *cq_host;
> +	u32 cq_ssc1_time;
>  };
>  
>  static const struct mtk_mmc_compatible mt2701_compat = {
> @@ -2450,9 +2451,48 @@ static void msdc_hs400_enhanced_strobe(struct mmc_host *mmc,
>  	}
>  }
>  
> +static void msdc_cqe_cit_cal(struct msdc_host *host, u64 timer_ns)
> +{
> +	struct mmc_host *mmc = mmc_from_priv(host);
> +	struct cqhci_host *cq_host = mmc->cqe_private;
> +	u8 itcfmul;
> +	u64 hclk_freq;
> +	u64 value;
> +
> +	/* Since MSDC CQE uses msdc_hclk as ITCFVAL, so driver should use hclk
> +	 * frequency to get the actual time for CIT.
> +	 */
> +	hclk_freq = clk_get_rate(host->h_clk);
> +	itcfmul = CQHCI_CAP_ITCFMUL(cqhci_readl(cq_host, CQHCI_CAP));
> +	switch (itcfmul) {
> +	case 0x0:
> +		do_div(hclk_freq, 1000);
> +		break;
> +	case 0x1:
> +		do_div(hclk_freq, 100);
> +		break;
> +	case 0x2:
> +		do_div(hclk_freq, 10);
> +		break;
> +	case 0x3:
> +		break;
> +	case 0x4:
> +		hclk_freq = hclk_freq * 10;
> +		break;
> +	default:
> +		host->cq_ssc1_time = 0x40;
> +		return;
> +	}
> +
> +	value = hclk_freq * timer_ns;
> +	do_div(value, 1000000000);
> +	host->cq_ssc1_time = value;
> +}
> +
>  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 +2502,9 @@ 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);
> +
> +	/* Set the send status command idle timer */
> +	cqhci_writel(cq_host, host->cq_ssc1_time, CQHCI_SSC1);

What about Send Status Command Block Counter (CBC) bits 19:16 ?

>  }
>  
>  static void msdc_cqe_disable(struct mmc_host *mmc, bool recovery)
> @@ -2803,6 +2846,8 @@ static int msdc_drv_probe(struct platform_device *pdev)
>  		/* cqhci 16bit length */
>  		/* 0 size, means 65536 so we don't have to -1 here */
>  		mmc->max_seg_size = 64 * 1024;
> +		/* Reduce CIT to 0x40 that corresponds to 2.35us */
> +		msdc_cqe_cit_cal(host, 2350);
>  	}
>  
>  	ret = devm_request_irq(&pdev->dev, host->irq, msdc_irq,