linux-kernel - Re: [PATCH 3/8] mmc: tegra: Implement HS400 enhanced strobe

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Message-ID: <20180809114345.GL21639@ulmo>
Date:   Thu, 9 Aug 2018 13:43:45 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Aapo Vienamo <avienamo@...dia.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] mmc: tegra: Implement HS400 enhanced strobe

On Tue, Aug 07, 2018 at 04:59:59PM +0300, Aapo Vienamo wrote:
> Implement HS400 enhanced strobe.

Can you provide a little more information about what the impact is of
this? Does this increase throughput? How much?

> 
> Signed-off-by: Aapo Vienamo <avienamo@...dia.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 426f7ea..d81143b 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -43,6 +43,9 @@
>  #define SDHCI_CLOCK_CTRL_PADPIPE_CLKEN_OVERRIDE		BIT(3)
>  #define SDHCI_CLOCK_CTRL_SPI_MODE_CLKEN_OVERRIDE	BIT(2)
>  
> +#define SDHCI_TEGRA_VENDOR_SYS_SW_CTRL			0x104
> +#define SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE		BIT(31)
> +
>  #define SDHCI_TEGRA_VENDOR_CAP_OVERRIDES		0x10c
>  #define SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_MASK		0x00003f00
>  #define SDHCI_TEGRA_CAP_OVERRIDES_DQS_TRIM_SHIFT	8
> @@ -271,6 +274,22 @@ static void tegra_sdhci_set_tap(struct sdhci_host *host, unsigned int tap)
>  	}
>  }
>  
> +static void tegra_sdhci_hs400_enhanced_strobe(struct mmc_host *mmc,
> +					      struct mmc_ios *ios)
> +{
> +	struct sdhci_host *host = mmc_priv(mmc);
> +	u32 reg;
> +
> +	reg = sdhci_readl(host, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);
> +	pr_err("enhanced strobe: %d\n", ios->enhanced_strobe);

Left-over debug error?

> +	if (ios->enhanced_strobe)
> +		reg |= SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
> +	else
> +		reg &= ~SDHCI_TEGRA_SYS_SW_CTRL_ENHANCED_STROBE;
> +	sdhci_writel(host, reg, SDHCI_TEGRA_VENDOR_SYS_SW_CTRL);

You might want to add blank lines around the if ... else ... block for
readability.

Thierry

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