linux-kernel - Re: [PATCH v2 1/3] mmc: core: Add mmc_regulator_set

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Message-ID: <CAL1qeaEGYwTCf0xasMZhGHEDWYhddLAS9jYjdgrccSwnFOc+7A@mail.gmail.com>
Date:	Mon, 15 Dec 2014 15:42:23 -0800
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Mark Brown <broonie@...nel.org>,
	Alexandru Stan <amstan@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Chris Ball <chris@...ntf.net>, johan.rudholm@...s.com,
	tim.kryger@...il.com, andrew_gabbasov@...tor.com,
	Adrian Hunter <adrian.hunter@...el.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] mmc: core: Add mmc_regulator_set_vqmmc()

Hi Doug,

On Mon, Dec 15, 2014 at 3:25 PM, Doug Anderson <dianders@...omium.org> wrote:
> This adds logic to the MMC core to set VQMMC.  This is expected to be
> called by MMC drivers like dw_mmc as part of (or instead of) their
> start_signal_voltage_switch() callback.
>
> A few notes:
>
> * When setting the signal voltage to 3.3V we do our best to make VQMMC
>   and VMMC match.  It's been reported that this makes some old cards
>   happy since they were tested back in the day before UHS when VQMMC
>   and VMMC were provided by the same regulator.  A nice side effect of
>   this is that we don't end up on the hairy edge of VQMMC (2.7V),
>   which some EEs claim is a little too close to the minimum for
>   comfort.
>
> * When setting the signal voltage to 1.8V or 1.2V we aim for that
>   specific voltage instead of picking the lowest one in the range.
>
> * We very purposely don't print errors in mmc_regulator_set_vqmmc().
>   There are cases where the MMC core will try several different
>   voltages and we don't want to pollute the logs.
>
> Signed-off-by: Doug Anderson <dianders@...omium.org>

Looks good to me.

Reviewed-by: Andrew Bresticker <abrestic@...omium.org>
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