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From: Doug Anderson <dianders@chromium.org>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Mark Brown <broonie@kernel.org>, Heiko Stuebner <heiko@sntech.de>,
	Jaehoon Chung <jh80.chung@samsung.com>,
	Seungwon Jeon <tgih.jun@samsung.com>,
	Alexandru Stan <amstan@chromium.org>,
	Alim Akhtar <alim.akhtar@samsung.com>,
	Sonny Rao <sonnyrao@chromium.org>,
	Andrew Bresticker <abrestic@chromium.org>,
	Addy Ke <addy.ke@rock-chips.com>,
	Javier Martinez Canillas <javier.martinez@collabora.co.uk>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	Chris Ball <chris@printf.net>,
	Johan Rudholm <johan.rudholm@axis.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Tim Kryger <tim.kryger@gmail.com>,
	Andrew Gabbasov <andrew_gabbasov@mentor.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	linux-mmc <linux-mmc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 2/4] mmc: core: Add mmc_regulator_set_vqmmc()
Date: Wed, 18 Mar 2015 21:09:33 -0700	[thread overview]
Message-ID: <CAD=FV=X=1=AnXCGgWWkJDcHLO-MfVqsSB2aJxi3WOgWJhD_ggA@mail.gmail.com> (raw)
In-Reply-To: <CAPDyKFpG=q88QEkuAgoLqkZU40Kx7dB7PmnXHqEt0EtbYvR_Cg@mail.gmail.com>

Ulf,

On Tue, Mar 17, 2015 at 3:23 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>> This will get us within .3V of whatever vmmc is.  If vmmc is 3.3V, it
>> will allow vqmmc of 3.0V - 3.6V.
>>
>> This _seems_ sane to me and given any sane system design we should be
>> fine here, I think.  I can't see someone designing a system where
>> vqmmc was not within .3V of vmmc, can you?  If we think someone will
>> actually build a system where vmmc is 3.3V and vqmmc can't go higher
>> than 2.7V then we'll either need to increase the tolerance here or add
>> a new asymmetric system call like my original patches did.
>
> I know about SoC that supports 3.4V vmmc and 2.9V vqmmc.
>
> What I think we need is the option to have a policy here. We need to
> allow voltage levels stated by the spec and at the same time try chose
> the one best suited. That's not being accomplished here.
>
> Moreover, I wonder whether it's okay (from spec perspective) to have
> vqmmc at a higher voltage level than vmmc. I don't think that's
> allowed, but I might be wrong.

OK, so sounds like I need to add a regulator_set_voltage_tol2()
function that takes in an upper tolerance and a lower.  We can use the
same rough implementation in the core we have today (if Mark is OK
with that) with regulator_set_voltage_tol() but just allow it to be
asymmetric.

>From what I see in the spec for 3.3V cards are supposed to react to a
high signal that is .625 * VDD - VDD + .3


I might not be able to get to this till next week, though...

-Doug

  parent reply	other threads:[~2015-03-19  4:09 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-11 22:15 [PATCH v4 1/4] mmc: dw_mmc: Don't try to enable the CD until we're sure we're not deferring Doug Anderson
2015-03-11 22:15 ` [PATCH v4 2/4] mmc: core: Add mmc_regulator_set_vqmmc() Doug Anderson
2015-03-16 14:05   ` Ulf Hansson
2015-03-16 15:12     ` Doug Anderson
2015-03-17 10:23       ` Ulf Hansson
2015-03-17 10:38         ` Mark Brown
2015-03-17 11:28           ` Ulf Hansson
2015-03-19  4:09         ` Doug Anderson [this message]
2015-03-19 11:14           ` Ulf Hansson
2015-03-19 11:36             ` Mark Brown
2015-03-20 10:55               ` Ulf Hansson
2015-03-20 11:28                 ` Mark Brown
2015-04-07 20:05                   ` Doug Anderson
2015-04-08 11:28                     ` Mark Brown
2015-03-11 22:15 ` [PATCH v4 3/4] mmc: dw_mmc: Use mmc_regulator_set_vqmmc in start_signal_voltage_switch Doug Anderson
2015-03-11 22:15 ` [PATCH v4 4/4] ARM: dts: Specify VMMC and VQMMC on rk3288-evb Doug Anderson
2015-03-11 23:30   ` Heiko Stuebner
2015-04-07 21:37     ` Heiko Stübner
2015-03-13 11:32 ` [PATCH v4 1/4] mmc: dw_mmc: Don't try to enable the CD until we're sure we're not deferring Jaehoon Chung
2015-03-13 12:10   ` Heiko Stuebner
2015-03-16  2:09     ` Jaehoon Chung
2015-03-27  5:55 ` Jaehoon Chung
2015-03-27 15:46   ` Doug Anderson

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