linux-kernel - RE: [PATCH V3 3/3] mmc: tegra: SDMMC pads auto-calibration

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Date:   Thu, 10 Jan 2019 19:19:47 +0000
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Thierry Reding <thierry.reding@...il.com>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        "Jonathan Hunter" <jonathanh@...dia.com>,
        "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
Subject: RE: [PATCH V3 3/3] mmc: tegra: SDMMC pads auto-calibration

>> @@ -805,6 +854,12 @@ static int tegra_sdhci_init_pinctrl_info(struct device *dev,
>>  		return -1;
>>  	}
>>  
>> +	tegra_host->pinctrl_state_1v8_drv = pinctrl_lookup_state(
>> +				tegra_host->pinctrl_sdmmc, "sdmmc-1v8-drv");
>> +
>> +	tegra_host->pinctrl_state_3v3_drv = pinctrl_lookup_state(
>> +				tegra_host->pinctrl_sdmmc, "sdmmc-3v3-drv");
>
>If this truly is optional, then I suggest we do something like this
>instead:

On tegra210, these settings are part of pinmux so using pinctrl to pinmux device node with existing properties pull-up and pull-down strength to configure timeout values.
On tegra186 and later, these settings are part of sdmmc controller itself so using existing pullup and pulldown timeout properties within sdmmc device node itself.

>From sdhci driver perspective, if pinctrl state exists (which is the case of tegra210), it uses it to configure drive settings otherwise (tegra186 & tegra194) it configures drive settings in pad register with in sdmmc domain itself.
So in away presence of sdmmc-1v8-drv and sdmmc-3v3-drv state is optional as they apply only for tegra210.
>From sdhci-tegra drive perspective,  it shouldn't return error on absence of these states as these states are not used for tegra186 and tegra194 and instead use drive strengths time out properties.
Will add check in drive to return error on absence of both sdmmc-3v3-drv, sdmmc-1v8-drv pinctrl states along with drive settings properties with in sdmmc device node...

>
>	tegra_host->pinctrl_state_1v8_drv = pinctrl_lookup_state(...);
>	if (IS_ERR(tegra_host->pinctrl_state_1v8_drv)) {
>		err = PTR_ERR(tegra_host->pinctrl_state_1v8_drv);
>
>		if (err == -ENODEV)
>			tegra_host->pinctrl_state_1v8_drv = NULL;
>		else
>			return err;
>	}
>
>With that we can use the much simpler condition everywhere:
>
>	if (tegra_host->pinctrl_state_1v8_drv)
>		...
>
>Thierry