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

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Date:	Fri, 25 Apr 2014 14:33:35 -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

Hi Tim,

> It is important that callers of mmc_regulator_get_supply know if either
> vmmc or vqmmc are present but not yet available.  To support this need,
> modify this function to return zero except when either of the regulator
> get operations fail with -EPROBE_DEFER.  Current callers don't check the
> return value and may continue to use IS_ERR on the vmmc/vqmmc values to
> determine if those regulators are available.  Furthermore, since all of
> these callers are capable of dealing with absent regulators, switch over
> to use the non-optional variety of the regulator get call.
>
> Signed-off-by: Tim Kryger <tim.kryger@...aro.org>
> ---
>  drivers/mmc/core/core.c |   27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index acbc3f2..095eef0 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1313,21 +1313,28 @@ EXPORT_SYMBOL_GPL(mmc_regulator_set_ocr);
>  int mmc_regulator_get_supply(struct mmc_host *mmc)
>  {
>         struct device *dev = mmc_dev(mmc);
> -       struct regulator *supply;
>         int ret;
>
> -       supply = devm_regulator_get(dev, "vmmc");
> -       mmc->supply.vmmc = supply;
> +       mmc->supply.vmmc = devm_regulator_get_optional(dev, "vmmc");
>         mmc->supply.vqmmc = devm_regulator_get_optional(dev, "vqmmc");
>
> -       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?

Thanks,
Andrew

>
> -       ret = mmc_regulator_get_ocrmask(supply);
> -       if (ret > 0)
> -               mmc->ocr_avail = ret;
> -       else
> -               dev_warn(mmc_dev(mmc), "Failed getting OCR mask: %d\n", ret);
> +       if (IS_ERR(mmc->supply.vqmmc)) {
> +               if (PTR_ERR(mmc->supply.vqmmc) == -EPROBE_DEFER)
> +                       return -EPROBE_DEFER;
> +               dev_info(dev, "No vqmmc regulator found\n");
> +       }
>
>         return 0;
>  }
> --
> 1.7.9.5
>
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