Re: [PATCH] mmc: mxs-mmc: Disable the 'reg_vmmc' regulator when needed

From: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Sascha Hauer <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	dl-linux-imx <linux-imx@nxp.com>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	Doug Anderson <dianders@chromium.org>,
	Rui Miguel Silva <rmfrfs@gmail.com>, Chris Ball <cjb@laptop.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-mmc <linux-mmc@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] mmc: mxs-mmc: Disable the 'reg_vmmc' regulator when needed
Date: Tue, 25 May 2021 21:31:55 +0200	[thread overview]
Message-ID: <7c973bfd-8fc3-026d-351c-dc00e92c8b01@wanadoo.fr> (raw)
In-Reply-To: <CAPDyKFrS3wdYs3AQtjZEOsLzNvxgy1n3EfxZ+a8w8J8rH8kQ-w@mail.gmail.com>

Le 24/05/2021 à 15:59, Ulf Hansson a écrit :
> On Fri, 21 May 2021 at 14:36, Christophe JAILLET
> <christophe.jaillet@wanadoo.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@wanadoo.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.

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.

CJ

> 
>>          }
>>
>>          ssp->clk = devm_clk_get(&pdev->dev, NULL);
>> --
>> 2.30.2
>>
> 
> Kind regards
> Uffe
> 