linux-kernel - Re: [PATCH 3/4] mmc: mmci: Ensure return value of regulator

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Date:	Fri, 3 May 2013 10:01:53 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	arnd@...db.de, linus.walleij@...ricsson.com,
	srinidhi.kasagar@...ricsson.com,
	Russell King <linux@....linux.org.uk>,
	Chris Ball <cjb@...top.org>
Subject: Re: [PATCH 3/4] mmc: mmci: Ensure return value of regulator_enable()
 is checked

On 2 May 2013 17:48, Lee Jones <lee.jones@...aro.org> wrote:
> This patch suppresses the warning below:
>
> drivers/mmc/host/mmci.c: In function ‘mmci_set_ios’:
> drivers/mmc/host/mmci.c:1165:20: warning: ignoring return value of
>         ‘regulator_enable’, declared with attribute warn_unused_result
>         [-Wunused-result]
>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Chris Ball <cjb@...top.org>
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  drivers/mmc/host/mmci.c |    9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index 375c109..f4f3038 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -1130,6 +1130,7 @@ static void mmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>         struct variant_data *variant = host->variant;
>         u32 pwr = 0;
>         unsigned long flags;
> +       int ret;
>
>         pm_runtime_get_sync(mmc_dev(mmc));
>
> @@ -1161,8 +1162,12 @@ static void mmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>                 break;
>         case MMC_POWER_ON:
>                 if (!IS_ERR(mmc->supply.vqmmc) &&
> -                   !regulator_is_enabled(mmc->supply.vqmmc))

I realize that we actually have a bug here (and in the MMC_POWER_OFF
mode as well).

We shall not use regulator_is_enabled API as a trigger to enable/fetch
a reference to the regulator, since it will only tell us if the
regulator is enabled - hw wise.
Instead we need a local variable in the mmci host struct keeping track
if we have enabled the regulator. Do you mind fix this up in this
patch as well since it is tightly coupled to the regulator handling!?

Otherwise it looks good to me.

Kind regards
Ulf Hansson

> -                       regulator_enable(mmc->supply.vqmmc);
> +                   !regulator_is_enabled(mmc->supply.vqmmc)) {
> +                       ret = regulator_enable(mmc->supply.vqmmc);
> +                       if (ret < 0)
> +                               dev_err(mmc_dev(mmc),
> +                                       "failed to enable vqmmc regulator\n");
> +               }
>
>                 pwr |= MCI_PWR_ON;
>                 break;
> --
> 1.7.10.4
>
> --
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