Re: [PATCH] mmc: core: Quieten "could not set regulator OCR" error.

[Chris Ball <cjb@laptop.org>]

Hi, adding Mark and Liam,

On Wed, Aug 29 2012, Ulf Hansson wrote:
> On 28 August 2012 01:33, Chris Ball <cjb@laptop.org> wrote:
>> Some distributions build with CONFIG_REGULATOR_DUMMY=y -- this makes
>> regulator setup succeed harmlessly, but then trying to set the voltage
>> on the dummy regulator will fail as below:
>>
>> [ 6.413866] sdhci-pci 0000:03:00.0: SDHCI controller found [1180:e822]
>> (rev 0)
>> [ 6.414081] _regulator_get: 0000:03:00.0 supply vmmc not found, using
>> dummy regulator
>> [ 6.415252] mmc0: SDHCI controller on PCI [0000:03:00.0] using DMA
>> [ 6.415294] sdhci-pci 0000:03:00.0: could not set regulator OCR (-22)
>> [ 6.444241] sdhci-pci 0000:03:00.0: could not set regulator OCR (-22)
>> [ 6.473648] sdhci-pci 0000:03:00.0: could not set regulator OCR (-22)
>> [..]
>>
>> Since this isn't an error in this case, move the error to pr_debug().
>> Reference: https://bugs.archlinux.org/task/29008
>>
>> Signed-off-by: Chris Ball <cjb@laptop.org>
>> ---
>>  drivers/mmc/core/core.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 835c9f0..30d9357 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -1017,8 +1017,9 @@ int mmc_regulator_set_ocr(struct mmc_host *mmc,
>>         }
>>
>>         if (result)
>> -               dev_err(mmc_dev(mmc),
>> -                       "could not set regulator OCR (%d)\n", result);
>> +               pr_debug("%s: could not set regulator OCR (%d)\n",
>> +                        mmc_hostname(mmc), result);
>> +
>
> I am not sure this is the correct solution. Would it be possible
> prevent sdhci-* from calling mmc_regulator_set_ocr when it has gotten
> a "dummy" regulator some how?

Looks like regulator_desc->name should be "dummy", but I think it would
be an API violation for us to start caring about that.  Mark, would you
be interested in offering an "regulator_is_dummy(supply)" function so
that we can limit our error messages to non-dummy supplies?

> In the other scenarios were we use a real regulator, I would interpret
> this error as critical, since the power to the card could not be set
> according to the vdd bit.
> Of course an option could be to leave the error printing to the caller
> of mmc_regulator_set_ocr.. :-)

Makes sense.  If we can't work out a compromise, we should just leave
it as-is -- the error messages appear to be worrying some users, but
they're not breaking any functionality.

Thanks for the review,

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child