linux-kernel - Re: [PATCH] sdhci: tegra: Avoid reading autocal timeout values when not applicable

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Date:   Fri, 22 May 2020 14:26:44 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     adrian.hunter@...el.com, ulf.hansson@...aro.org,
        jonathanh@...dia.com, digetx@...il.com,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org
Subject: Re: [PATCH] sdhci: tegra: Avoid reading autocal timeout values when
 not applicable

On Wed, May 20, 2020 at 01:08:57PM -0700, Sowjanya Komatineni wrote:
> When auto calibration timeouts, calibration is disabled and fail-safe
> drive strength values are programmed based on the signal voltage.
> 
> Different fail-safe drive strength values based on voltage are
> applicable only for SoCs supporting 3V3 and 1V8 pad controls.
> 
> So, this patch avoids reading these properties from the device tree
> for SoCs not using pad controls and the warning of missing properties
> will not show up on these SoC platforms.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c | 57 ++++++++++++++++++++++++------------------
>  1 file changed, 33 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 3e2c510..141b49b 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -605,6 +605,39 @@ static void tegra_sdhci_parse_pad_autocal_dt(struct sdhci_host *host)
>  		autocal->pull_down_1v8 = 0;
>  
>  	err = device_property_read_u32(host->mmc->parent,
> +			"nvidia,pad-autocal-pull-up-offset-sdr104",
> +			&autocal->pull_up_sdr104);
> +	if (err)
> +		autocal->pull_up_sdr104 = autocal->pull_up_1v8;
> +
> +	err = device_property_read_u32(host->mmc->parent,
> +			"nvidia,pad-autocal-pull-down-offset-sdr104",
> +			&autocal->pull_down_sdr104);
> +	if (err)
> +		autocal->pull_down_sdr104 = autocal->pull_down_1v8;
> +
> +	err = device_property_read_u32(host->mmc->parent,
> +			"nvidia,pad-autocal-pull-up-offset-hs400",
> +			&autocal->pull_up_hs400);
> +	if (err)
> +		autocal->pull_up_hs400 = autocal->pull_up_1v8;
> +
> +	err = device_property_read_u32(host->mmc->parent,
> +			"nvidia,pad-autocal-pull-down-offset-hs400",
> +			&autocal->pull_down_hs400);
> +	if (err)
> +		autocal->pull_down_hs400 = autocal->pull_down_1v8;
> +
> +	/*
> +	 * Different fail-safe drive strength values based on the signaling
> +	 * voltage are applicable for SoCs supporting 3V3 and 1V8 pad controls.
> +	 * So, avoid reading below device tree properies for SoCs that don't
> +	 * have NVQUIRK_NEEDS_PAD_CONTROL.
> +	 */
> +	if (!(tegra_host->soc_data->nvquirks & NVQUIRK_NEEDS_PAD_CONTROL))
> +		return;

Hm... so what exactly is the difference between NVQUIRK_HAS_PADCALIB? I
think Tegra30 will also end up calling tegra_sdhci_set_padctrl(), but it
will then write the default (0) value for these drive strength. Is that
okay?

Thierry

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