linux-kernel - Re: [PATCH 03/10] mmc: tegra: Power on the calibration pad

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Date:   Wed, 25 Jul 2018 10:11:34 +0300
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Aapo Vienamo <avienamo@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mikko Perttunen <mperttunen@...dia.com>
Cc:     linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/10] mmc: tegra: Power on the calibration pad

Reviewed-by: Mikko Perttunen <mperttunen@...dia.com>

On 24.07.2018 17:34, Aapo Vienamo wrote:
> Automatic pad drive strength calibration is performed on a separate pad
> identical to the ones used for driving the actual bus. Power on the
> calibration pad during the calibration procedure and power it off
> afterwards to save power.
> 
> Signed-off-by: Aapo Vienamo <avienamo@...dia.com>
> ---
>   drivers/mmc/host/sdhci-tegra.c | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 6008e2f..61067b7 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -209,11 +209,30 @@ static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
>   	tegra_host->ddr_signaling = false;
>   }
>   
> +static void tegra_sdhci_configure_cal_pad(struct sdhci_host *host, bool enable)
> +{
> +	u32 reg;
> +
> +	/*
> +	 * Enable or disable the additional I/O pad used by the drive strength
> +	 * calibration process.
> +	 */
> +	reg = sdhci_readl(host, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
> +	if (enable)
> +		reg |= SDHCI_TEGRA_PAD_E_INPUT_OR_E_PWRD;
> +	else
> +		reg &= ~SDHCI_TEGRA_PAD_E_INPUT_OR_E_PWRD;
> +	sdhci_writel(host, reg, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
> +	udelay(1);
> +}
> +
>   static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
>   {
>   	unsigned timeout = 10;
>   	u32 reg;
>   
> +	tegra_sdhci_configure_cal_pad(host, true);
> +
>   	reg = sdhci_readl(host, SDHCI_TEGRA_AUTO_CAL_CONFIG);
>   	reg |= SDHCI_AUTO_CAL_ENABLE | SDHCI_AUTO_CAL_START;
>   	sdhci_writel(host, reg, SDHCI_TEGRA_AUTO_CAL_CONFIG);
> @@ -227,6 +246,8 @@ static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
>   		timeout--;
>   	} while (timeout);
>   
> +	tegra_sdhci_configure_cal_pad(host, false);
> +
>   	if (timeout == 0)
>   		dev_err(mmc_dev(host->mmc), "Pad autocal timed out\n");
>   }
>