linux-kernel - Re: [PATCH RESEND] mmc: core: Improve support for deferred regulators

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Message-ID: <CAL1qeaH6uzMX-3P7D5aZRx1aZyHyMX0wz=zKPrBOxPcQJedYdw@mail.gmail.com>
Date:	Tue, 29 Apr 2014 10:36:33 -0700
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Tim Kryger <tim.kryger@...aro.org>
Cc:	Chris Ball <chris@...ntf.net>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Mike Looijmans <mike.looijmans@...ic.nl>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] mmc: core: Improve support for deferred regulators

On Tue, Apr 29, 2014 at 10:00 AM, Tim Kryger <tim.kryger@...aro.org> wrote:
> On Fri, Apr 25, 2014 at 2:33 PM, Andrew Bresticker
> <abrestic@...omium.org> wrote:
>>>
>>> -       if (IS_ERR(supply))
>>> -               return PTR_ERR(supply);
>>> +       if (IS_ERR(mmc->supply.vmmc)) {
>>> +               if (PTR_ERR(mmc->supply.vmmc) == -EPROBE_DEFER)
>>> +                       return -EPROBE_DEFER;
>>> +               dev_info(dev, "No vmmc regulator found\n");
>>> +       } else {
>>> +               ret = mmc_regulator_get_ocrmask(mmc->supply.vmmc);
>>> +               if (ret > 0)
>>> +                       mmc->ocr_avail = ret;
>>> +               else
>>> +                       dev_warn(dev, "Failed getting OCR mask: %d\n", ret);
>>> +       }
>>
>> I think we also need to handle the case where supply is NULL, i.e.
>> !CONFIG_REGULATOR.  The SDHCI driver, for example, calls
>> regulator_is_supported_voltage() which will always return false on
>> NULL regulators.  Perhaps we should set the supplies to
>> ERR_PTR(-ENODEV) in that case?
>
> As of v3.15-rc3, this function would do the right thing because
> df7926f modified the regulator get optional stubs to return -ENODEV in
> the !CONFIG_REGULATOR case.  However, this implementation of
> mmc_regulator_get_supply doesn't actually get built for that case.  A
> stub implementation is used instead.  Presently that stub
> mmc_regulator_get_supply does nothing other than return zero but
> perhaps it should initialize the supplies as you suggest.
> Alternatively, the stub could be eliminated such that this
> implementation is used in all cases.  Do you have a preference?

Since this now behaves correctly regardless of CONFIG_REGULATOR, then
perhaps it's best to eliminate the stub.

Thanks,
Andrew

>
> -Tim
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