linux-kernel - Re: [PATCH 02/10] mmc: tegra: Set calibration pad voltage reference

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Message-ID: <d5018027-f333-8432-f8ed-81a2cdfedea8@kapsi.fi>
Date:   Wed, 25 Jul 2018 10:08:46 +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 02/10] mmc: tegra: Set calibration pad voltage reference

On 24.07.2018 17:34, Aapo Vienamo wrote:
> Configure the voltage reference used by the automatic pad drive strength
> calibration procedure. The value is a magic number from the TRM.
> 
> Signed-off-by: Aapo Vienamo <avienamo@...dia.com>
> ---
>   drivers/mmc/host/sdhci-tegra.c | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index e40ca43..6008e2f 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -49,6 +49,10 @@
>   #define SDHCI_AUTO_CAL_START			BIT(31)
>   #define SDHCI_AUTO_CAL_ENABLE			BIT(29)
>   
> +#define SDHCI_TEGRA_SDMEM_COMP_PADCTRL			0x1e0
> +#define SDHCI_TEGRA_SDMEM_COMP_PADCTRL_VREF_SEL_MASK	0x0000000f
> +#define SDHCI_TEGRA_SDMEM_COMP_PADCTRL_VREF_SEL_VAL	0x7
> +
>   #define SDHCI_TEGRA_AUTO_CAL_STATUS     0x1ec
>   #define SDHCI_TEGRA_AUTO_CAL_ACTIVE     BIT(31)
>   
> @@ -152,7 +156,7 @@ static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
>   	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>   	struct sdhci_tegra *tegra_host = sdhci_pltfm_priv(pltfm_host);
>   	const struct sdhci_tegra_soc_data *soc_data = tegra_host->soc_data;
> -	u32 misc_ctrl, clk_ctrl;
> +	u32 misc_ctrl, clk_ctrl, pad_ctrl;
>   
>   	sdhci_reset(host, mask);
>   
> @@ -193,8 +197,14 @@ static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
>   	sdhci_writel(host, misc_ctrl, SDHCI_TEGRA_VENDOR_MISC_CTRL);
>   	sdhci_writel(host, clk_ctrl, SDHCI_TEGRA_VENDOR_CLOCK_CTRL);
>   
> -	if (soc_data->nvquirks & NVQUIRK_HAS_PADCALIB)
> +	if (soc_data->nvquirks & NVQUIRK_HAS_PADCALIB) {
> +		pad_ctrl = sdhci_readl(host, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
> +		pad_ctrl &= ~SDHCI_TEGRA_SDMEM_COMP_PADCTRL_VREF_SEL_MASK;
> +		pad_ctrl |= SDHCI_TEGRA_SDMEM_COMP_PADCTRL_VREF_SEL_VAL;
> +		sdhci_writel(host, pad_ctrl, SDHCI_TEGRA_SDMEM_COMP_PADCTRL);
> +

Will this happen to only eMMC controllers or for all controllers? My 
docs are saying this should be set to 0x7 for SDMMC2/4 and 0x1 or 0x2 
for SDMMC1/3 depending on voltage. Not sure how downstream is 
programming it, though.

>   		tegra_host->pad_calib_required = true;
> +	}
>   
>   	tegra_host->ddr_signaling = false;
>   }
>