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From: Thierry Reding <thierry.reding@gmail.com>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Sowjanya Komatineni <skomatineni@nvidia.com>,
	adrian.hunter@intel.com, ulf.hansson@linaro.org,
	jonathanh@nvidia.com, linux-tegra@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mmc@vger.kernel.org
Subject: Re: [PATCH] sdhci: tegra: Avoid reading autocal timeout values when not applicable
Date: Fri, 22 May 2020 14:52:30 +0200
Message-ID: <20200522125230.GH2163848@ulmo> (raw)
In-Reply-To: <95d01fae-bf1f-28d1-2d11-8f5693646fa3@gmail.com>


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On Fri, May 22, 2020 at 03:42:18PM +0300, Dmitry Osipenko wrote:
> 22.05.2020 15:26, Thierry Reding пишет:
> > 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@nvidia.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?
> 
> It won't write 0, but skip the writing if values are 0. Technically T30+
> supports the customized strengths, but I'm not sure whether it was ever
> tested and whether it's really needed. I think Sowjanya said before that
> the default values are always okay for older SoCs.

Alright then, in that case:

Acked-by: Thierry Reding <treding@nvidia.com>

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  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-20 20:08 Sowjanya Komatineni
2020-05-21 12:40 ` Dmitry Osipenko
2020-05-22 12:26 ` Thierry Reding
2020-05-22 12:42   ` Dmitry Osipenko
2020-05-22 12:52     ` Thierry Reding [this message]
2020-05-22 15:11       ` Sowjanya Komatineni
2020-05-22 12:28 ` Dmitry Osipenko
2020-05-24 15:33 ` Adrian Hunter
2020-05-25  8:47 ` Ulf Hansson

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