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From: Doug Anderson <dianders@chromium.org>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Heiko Stuebner <heiko@sntech.de>,
	Jaehoon Chung <jh80.chung@samsung.com>,
	Seungwon Jeon <tgih.jun@samsung.com>,
	Mark Brown <broonie@kernel.org>,
	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: Mon, 16 Mar 2015 08:12:43 -0700	[thread overview]
Message-ID: <CAD=FV=U-YnT5jF5MFC==hANXGPqVpV3iLMPu85TrQ4dNDsWeCA@mail.gmail.com> (raw)
In-Reply-To: <CAPDyKFq_WMJfqNGuxwN7xPmhv2X6-+G1zXpdD6zYDkDe7-Jo2A@mail.gmail.com>

Ulf,

On Mon, Mar 16, 2015 at 7:05 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>> +       switch (ios->signal_voltage) {
>> +       case MMC_SIGNAL_VOLTAGE_120:
>> +               return mmc_regulator_set_voltage_if_supported(mmc->supply.vqmmc,
>> +                       1200000, 100000);
>
> Is 1V the lowest possible value? How did you get to that?

I think you've added a zero in your mind and not realized that I'm
calling regulator_set_voltage_tol() here and in other calls.  Please
read the above as:

* 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


>> +       case MMC_SIGNAL_VOLTAGE_180:
>> +               return mmc_regulator_set_voltage_if_supported(mmc->supply.vqmmc,
>> +                       1800000, 100000);
>
> Is 1V the lowest possible value? How did you get to that?

Again, check my zeros.  This should be 1.7 - 1.9V, aiming for 1.8V.


>> +       case MMC_SIGNAL_VOLTAGE_330:
>> +               return mmc_regulator_set_voltage_if_supported(mmc->supply.vqmmc,
>> +                       regulator_get_voltage(mmc->supply.vmmc), 300000);
>
> Why 3V? Shouldn't it be 2.7V? How will else those SoC that for example
> supports 2.9V only work?

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.

>>  int mmc_regulator_get_supply(struct mmc_host *mmc);
>
> One more thought,s as for the vmmc regulator we have a
> "regulator_enabled" member in the mmc_host. Should we add a similar
> member for vqmmc? That would prevent host drivers from keeping track
> of this state themselves.

Yeah, that does sound nice.  Are you suggesting that I modify this
patch or submit a new one.  Let me know.


-Doug

  reply	other threads:[~2015-03-16 15:12 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 [this message]
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
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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