linux-kernel - Re: [PATCH v4 2/4] mmc: core: Add mmc_regulator_set

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Message-ID: <CAPDyKFqGYqNCbGGzw7orXLT+pkxK5LMUDTYWju405tqynPMyCQ@mail.gmail.com>
Date:	Tue, 17 Mar 2015 12:28:34 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Doug Anderson <dianders@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Alexandru Stan <amstan@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	Andrew Bresticker <abrestic@...omium.org>,
	Addy Ke <addy.ke@...k-chips.com>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	"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 <johan.rudholm@...s.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Tim Kryger <tim.kryger@...il.com>,
	Andrew Gabbasov <andrew_gabbasov@...tor.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/4] mmc: core: Add mmc_regulator_set_vqmmc()

On 17 March 2015 at 11:38, Mark Brown <broonie@...nel.org> wrote:
> On Tue, Mar 17, 2015 at 11:23:33AM +0100, Ulf Hansson wrote:
>> On 16 March 2015 at 16:12, Doug Anderson <dianders@...omium.org> wrote:
>
>> > * Try to set the voltage to exactly 1,200,000 uV (1.2V).
>> > * If you can't get 1.2V exactly, a tolerance ("tol") of 100,000 uV
>> > (.1V) is OK.
>> > * In other words, 1.1V - 1.3V are OK, but aim for 1.2V
>
>> So what happens in the case when 1.3V and 1.1V, but not 1.2V. Which
>> value will be used? Is that algorithm defined by the regulator core or
>> does it depend per regulator implementation?
>
> It's done in the core.  It first tries to hit the target voltage to the
> maximum (picking the lowest voltage in that range) then tries to pick
> the lowest voltage to the target, though that's an implementation detail
> and we really should be trying to get as close as possible to the
> target.  We don't do that yet because it can be expensive to work out so
> we do the current thing which is cheap and mostly good enough.

Okay, so that seems to work well for our 1.1V->1.3V case.

Thanks!

Kind regards
Uffe
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