linux-kernel - Re: [PATCH] mmc: mxs-mmc: Disable the 'reg

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Date:   Wed, 26 May 2021 00:47:54 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Doug Anderson <dianders@...omium.org>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Chris Ball <cjb@...top.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] mmc: mxs-mmc: Disable the 'reg_vmmc' regulator when needed

On Tue, 25 May 2021 at 21:31, Christophe JAILLET
<christophe.jaillet@...adoo.fr> wrote:
>
> Le 24/05/2021 à 15:59, Ulf Hansson a écrit :
> > On Fri, 21 May 2021 at 14:36, Christophe JAILLET
> > <christophe.jaillet@...adoo.fr> wrote:
> >>
> >> The 'reg_vmmc' regulator is never disabled. Neither in the error handling
> >> of the probe, nor in the remove function.
> >>
> >> Add a managed action to do the required clean-up before a 'regulator_put()'
> >> call.
> >>
> >> Fixes: 4dc5a79f1350 ("mmc: mxs-mmc: enable regulator for mmc slot")
> >> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> >> ---
> >>   drivers/mmc/host/mxs-mmc.c | 11 +++++++++++
> >>   1 file changed, 11 insertions(+)
> >>
> >> diff --git a/drivers/mmc/host/mxs-mmc.c b/drivers/mmc/host/mxs-mmc.c
> >> index 947581de7860..b043d53dd728 100644
> >> --- a/drivers/mmc/host/mxs-mmc.c
> >> +++ b/drivers/mmc/host/mxs-mmc.c
> >> @@ -552,6 +552,13 @@ static const struct of_device_id mxs_mmc_dt_ids[] = {
> >>   };
> >>   MODULE_DEVICE_TABLE(of, mxs_mmc_dt_ids);
> >>
> >> +static void regulator_disable_action(void *_data)
> >> +{
> >> +       struct regulator *regulator = _data;
> >> +
> >> +       regulator_disable(regulator);
> >> +}
> >> +
> >>   static int mxs_mmc_probe(struct platform_device *pdev)
> >>   {
> >>          struct device_node *np = pdev->dev.of_node;
> >> @@ -591,6 +598,10 @@ static int mxs_mmc_probe(struct platform_device *pdev)
> >>                                  "Failed to enable vmmc regulator: %d\n", ret);
> >>                          goto out_mmc_free;
> >>                  }
> >> +               ret = devm_add_action_or_reset(&pdev->dev,
> >> +                                       regulator_disable_action, reg_vmmc);
> >> +               if (ret)
> >> +                       goto out_mmc_free;
> >
> > Even if this improves the behaviour, there is a standardized way for
> > how we deal with regulators for mmc.
> >
> > 1. Call mmc_regulator_get_supply() during probe to fetch the optional
> > regulator. If a regulator is found a corresponding OCR mask, in
> > host->ocr_avail is assigned.
> >
> > 2. In the ->set_ios() callback, invoke mmc_regulator_set_ocr(). This
> > will also set the correct voltage-level and turn on/off the regulator,
> > depending on the requested OCR/voltage-level.
>
> Hi,
> I don't know this API.
> I've tried to look at a few drivers to see how it was used, but it
> didn't help me either.

Okay.

>
> So, I won't be able to provide any other proposal on this. It would only
> be trial/error.
> It is yours if something needs to be fixed here.
>
> Anyway, thanks for your time for answering and trying to show the right
> direction.

If I put together some patch and submit it, would you be able help to
run some tests of it, as I don't have access to HW?

Kind regards
Uffe