Message-ID: <CADz5_gLfy69YksiFuxEKeAv387go_8cOcK_uxbKuhrTBrXdjdQ@mail.gmail.com>
Date:	Tue, 20 Nov 2012 23:24:50 +0800
From:	Kevin Liu <keyuan.liu@...il.com>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	Chris Ball <cjb@...top.org>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, kyungmin.park@...sung.com,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>, lrg@...com,
	Philip Rakity <prakity@...dia.com>
Subject: Re: FW: [PATCH v2] mmc: sdhci: apply voltage range check only for
 non-fixed regulators

2012/11/20 Marek Szyprowski <m.szyprowski@...sung.com>:
> Hello,
>
>
> On 11/20/2012 3:14 PM, Kevin Liu wrote:
>>
>> 2012/11/20 Marek Szyprowski <m.szyprowski@...sung.com>:
>> > Hello,
>> >
>> >
>> > On 11/20/2012 12:36 PM, Kevin Liu wrote:
>> >>
>> >> 2012/11/20 Marek Szyprowski <m.szyprowski@...sung.com>:
>> >> > On 11/20/2012 9:59 AM, Kevin Liu wrote:
>> >> >> 2012/11/20 Marek Szyprowski <m.szyprowski@...sung.com>:
>> >> >> > On 11/14/2012 8:11 AM, Kevin Liu wrote:
>> >> >> >>
>> >> >> >> > From: linux-mmc-owner@...r.kernel.org
>> >> >> >> > [mailto:linux-mmc-owner@...r.kernel.org] On Behalf Of Chris
>> >> >> >> > Ball
>> >> >> >> > Sent: Tuesday, November 13, 2012 10:14 PM
>> >> >> >> > To: Marek Szyprowski
>> >> >> >> > Cc: linux-kernel@...r.kernel.org; linux-mmc@...r.kernel.org;
>> >> >> >> > Kyungmin
>> >> >> >> > Park; Mark Brown; Liam Girdwood; Philip Rakity
>> >> >> >> > Subject: Re: [PATCH v2] mmc: sdhci: apply voltage range check
>> >> >> >> > only
>> >> >> >> > for non-fixed regulators
>> >> >> >> > On Tue, Nov 13 2012, Marek Szyprowski wrote:
>> >> >> >> >>> On Tue, Nov 13 2012, Marek Szyprowski wrote:
>> >> >> >> >>> > Fixed regulators cannot change their voltage, so disable
>> >> >> >> >>> > all
>> >> >> >> >>> > voltage
>> >> >> >> >>> > range checking for them, otherwise the driver fails to
>> >> >> >> >>> > operate
>> >> >> >> >>> > with
>> >> >> >> >>> > fixed regulators. Up to now it worked only by luck, because
>> >> >> >> >>> > regulator_is_supported_voltage() function returned
>> >> >> >> >>> > incorrect
>> >> >> >> >>> > values.
>> >> >> >> >>> > Commit "regulator: fix voltage check in
>> >> >> >> >>> > regulator_is_supported_voltage()"
>> >> >> >> >>> > fixed that function and now additional check is needed for
>> >> >> >> >>> > fixed
>> >> >> >> >>> > regulators.
>> >> >> >> >>> >
>> >> >> >> >>> > Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
>> >> >> >> >>> > ---
>> >> >> >> >>> >  drivers/mmc/host/sdhci.c |    2 +-
>> >> >> >> >>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >> >> >> >>> >
>> >> >> >> >>> > diff --git a/drivers/mmc/host/sdhci.c
>> >> >> >> >>> > b/drivers/mmc/host/sdhci.c
>> >> >> >> >>> > index c7851c0..6f6534e 100644
>> >> >> >> >>> > --- a/drivers/mmc/host/sdhci.c
>> >> >> >> >>> > +++ b/drivers/mmc/host/sdhci.c
>> >> >> >> >>> > @@ -2923,7 +2923,7 @@ int sdhci_add_host(struct sdhci_host
>> >> >> >> >>> > *host)
>> >> >> >> >>> >            regulator_enable(host->vmmc);
>> >> >> >> >>> >
>> >> >> >> >>> >  #ifdef CONFIG_REGULATOR
>> >> >> >> >>> > -  if (host->vmmc) {
>> >> >> >> >>> > +  if (host->vmmc && regulator_count_voltages(host->vmmc) >
>> >> >> >> >>> > 1)
>> >> >> >> >>> > {
>> >> >> >> >>> >            ret = regulator_is_supported_voltage(host->vmmc,
>> >> >> >> >>> > 3300000,
>> >> >> >> >>> >                    3300000);
>> >> >> >> >>> >            if ((ret <= 0) || (!(caps[0] &
>> >> >> >> >>> > SDHCI_CAN_VDD_330)))
>> >> >> >> >>>
>> >> >> >> >>> Thanks for the longer explanation.  I'm still missing
>> >> >> >> >>> something,
>> >> >> >> >>> though;
>> >> >> >> >>> what's wrong with running the check as it was with the new
>> >> >> >> >>> regulator
>> >> >> >> >>> code?
>> >> >> >> >>> (I haven't tried it yet.)
>> >> >> >> >>>
>> >> >> >> >>> #ifdef CONFIG_REGULATOR
>> >> >> >> >>>          if (host->vmmc) {
>> >> >> >> >>>                  ret =
>> >> >> >> >>> regulator_is_supported_voltage(host->vmmc,
>> >> >> >> >>> 3300000,
>> >> >> >> >>>                          3300000);
>> >> >> >> >>>                  if ((ret <= 0) || (!(caps[0] &
>> >> >> >> >>> SDHCI_CAN_VDD_330)))
>> >> >> >> >>>                          caps[0] &= ~SDHCI_CAN_VDD_330;
>> >> >> >> >>>                  ret =
>> >> >> >> >>> regulator_is_supported_voltage(host->vmmc,
>> >> >> >> >>> 3000000,
>> >> >> >> >>>                          3000000);
>> >> >> >> >>>                  if ((ret <= 0) || (!(caps[0] &
>> >> >> >> >>> SDHCI_CAN_VDD_300)))
>> >> >> >> >>>                          caps[0] &= ~SDHCI_CAN_VDD_300;
>> >> >> >> >>>                  ret =
>> >> >> >> >>> regulator_is_supported_voltage(host->vmmc,
>> >> >> >> >>> 1800000,
>> >> >> >> >>>                          1800000);
>> >> >> >> >>>                  if ((ret <= 0) || (!(caps[0] &
>> >> >> >> >>> SDHCI_CAN_VDD_180)))
>> >> >> >> >>>                          caps[0] &= ~SDHCI_CAN_VDD_180;
>> >> >> >> >>>          }
>> >> >> >> >>> #endif /* CONFIG_REGULATOR */
>> >> >> >> >>>
>> >> >> >> >>> The point is to remove unsupported voltages, so if someone
>> >> >> >> >>> sets
>> >> >> >> >>> up
>> >> >> >> >>> a
>> >> >> >> >>> fixed regulator at 3300000, all of the other caps are
>> >> >> >> >>> disabled.
>> >> >> >> >>> Why
>> >> >> >> >>> wouldn't that work without this change, and how are we
>> >> >> >> >>> supposed
>> >> >> >> >>> to
>> >> >> >> >>> remove those caps on a fixed regulator after your patchset?
>> >> >> >> >>>
>> >> >> >> >>> Thanks, sorry if I'm missing something obvious,
>> >> >> >> >>
>> >> >> >> >> On our boards eMMC is connected to fixed 2.8V regulator, what
>> >> >> >> >> results
>> >> >> >> >> in
>> >> >> >> >> clearing all available voltages and fail. The same situation
>> >> >> >> >> is
>> >> >> >> >> when
>> >> >> >> >> one
>> >> >> >> >> enable dummy regulator and try to use sdhci with it. My patch
>> >> >> >> >> fixes
>> >> >> >> >> this
>> >> >> >> >> and restores sdhci to working state as it was before (before
>> >> >> >> >> fixing
>> >> >> >> >> regulator regulator_is_supported_voltage() function and
>> >> >> >> >> earlier
>> >> >> >> >> when
>> >> >> >> >> MMC_BROKEN_VOLATGE capability was used).
>> >> >> >> >
>> >> >> >> > I see.  Sounds like a separate bug -- Philip (or anyone else),
>> >> >> >> > any
>> >> >> >> > idea how we should be treating eMMCs with a fixed voltage here?
>> >> >> >> >
>> >> >> >>
>> >> >> >> I think we should check the voltage range rather than the voltage
>> >> >> >> point accoring to the spec.
>> >> >> >> Otherwise some valid voltage like 2.8v will be discarded by
>> >> >> >> mistake.
>> >> >> >> My below old patch aim to fix this issue.
>> >> >> >> How do you think?
>> >> >> >>
>> >> >> >> -----Original Message-----
>> >> >> >> From: Kevin Liu [mailto:keyuan.liu@...il.com]
>> >> >> >> Sent: Friday, September 28, 2012 3:56 PM
>> >> >> >> To: linux-mmc@...r.kernel.org; cjb@...top.org; pierre@...man.eu;
>> >> >> >> ulf.hansson@...aro.org; Zhangfei Gao
>> >> >> >> Cc: Haojian Zhuang; Chao Xie; Philip Rakity; Kevin Liu; Jialing
>> >> >> >> Fu
>> >> >> >> Subject: [PATCH v5 03/13] mmc: sdhci: use regulator min/max
>> >> >> >> voltage
>> >> >> >> range according to spec
>> >> >> >>
>> >> >> >> From: Kevin Liu <kliu5@...vell.com>
>> >> >> >>
>> >> >> >> For regulator vmmc/vmmcq, use voltage range as below
>> >> >> >> 3.3v/3.0v: (2.7v, 3.6v)
>> >> >> >> 1.8v: (1.7v, 1.95v)
>> >> >> >> Original code use the specific value which may fail in regulator
>> >> >> >> driver if it does NOT support the specific voltage.
>> >> >> >>
>> >> >> >> Signed-off-by: Jialing Fu <jlfu@...vell.com>
>> >> >> >> Signed-off-by: Kevin Liu <kliu5@...vell.com>
>> >> >> >
>> >> >> >
>> >> >> > Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
>> >> >> >
>> >> >> > This patch restores sdhci devices to working state on Samsung
>> >> >> > boards
>> >> >> > (tested on GONI and UniversalC210) after merging "regulator: fix
>> >> >> > voltage
>> >> >> > check in regulator_is_supported_voltage()" patch to v3.7-rc6
>> >> >> > (commit
>> >> >> > f0f98b19e23d4426ca185e3d4ca80e6aff5ef51b). Would be great to have
>> >> >> > it
>> >> >> > merged before the final v3.7 is out.
>> >> >> >
>> >> >> Marek,
>> >> >>
>> >> >> thanks a lot for the verification!
>> >> >> And your patch "mmc: sdhci: apply voltage range check only for
>> >> >> non-fixed regulators" (commit
>> >> >> d5b5205f2d480a47863dda0772d2d9dc47c2b51b, which has been merged in
>> >> >> mmc-next) can be reverted if this patch merged?
>> >> >
>> >> >
>> >> > Yes, it can be replaced with it, although there is still an issue
>> >> > that
>> >> > need
>> >> > to be resolved somehow. Right now SDHCI driver fails to initialize if
>> >> > support
>> >> > for dummy regulator is enabled.
>> >> >
>> >> Then I think the dummy issue can be resolved with your patch merged
>> >> and if you can just update your patch from
>> >>       "regulator_count_voltages(host->vmmc) > 1"
>> >> to
>> >>       "regulator_count_voltages(host->vmmc) > 0"
>> >> to let fix regulator work.
>> >
>> >
>> > regulator_count_voltages() returns 1 for both fixed regulators and for
>> > virtual dummy regulator, so the above change makes no sense.
>>
>> I think regulator_count_voltage should return -EINVAL for dummy
>> regulator since n_voltages is not defined for dummy regulator:
>> int regulator_count_voltages(struct regulator *regulator)
>> {
>>          struct regulator_dev    *rdev = regulator->rdev;
>>
>>          return rdev->desc->n_voltages ? : -EINVAL;
>> }
>> can you double check this?
>
>
> Err, right. I looked at the wrong SDHCI device :/ I have 3 of them on my
> board - one with fixed regulator, one with 'real' and one without (with
> virtual dummy regulator). I've applied my earlier patch and noticed that
> it cured sdhci driver with dummy regulator, so I concluded that it did
> the right job. Sorry for the confusion.
>
No problem, thanks for the check.

>> > However I was so focused on fixing the 2.8V supply case that I missed
>> > the
>> > fact that my "mmc: sdhci: apply voltage range check only for non-fixed
>> > regulators" patch also fixed the dummy regulator case.
>> >
>> > The conclusion is that applying both patches should finally fix the
>> > regulator issues with for the Samsung boards (2.8V supply for eMMC) and
>> > 'dummy-regulators' cases.
>> >
>>
>> After thinking again, I think we don't need the check for
>> regulator_count_voltages.
>> In fact, dummy regulator should NOT be used for the sd/mmc power
>> supply. We should use controllable or fixed regulator. If dummy
>> regulator is used, then it means we won't control it and we don't know
>> its voltage. It's not reasonable for sd/mmc power supply. If dummy
>> regulator is used, I think it's ok to return error and disable all
>> voltage support caps.
>
>
> The problem with dummy regulator is the fact that it can be enabled only
> globally for all devices in the system. I think that the best solution
> would be to introduce regulator_can_change_voltage() as Mark suggested.
> I will post patches soon.
>
I think both controllable and fixed regulator should check the voltage
range (fixed regulator also need to check its voltage whether resides
in the valid range). But regulator_can_change_voltage will return
false for both fixed and dummy regulator while return true for
controllable regulator.

Thanks
Kevin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists