linux-kernel - Re: [alsa-devel] [PATCH v3 2/2] ASoC: imx-wm8962: Fix codec

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Message-ID: <CAEnQRZAx1o9xtbf3u1A_Zun7MSaJjdjunpJm1Q6=ZAA3beoFbA@mail.gmail.com>
Date:   Tue, 28 Mar 2017 13:47:04 +0300
From:   Daniel Baluta <daniel.baluta@...il.com>
To:     Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Cc:     Daniel Baluta <daniel.baluta@....com>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        Mark Brown <broonie@...nel.org>, alsa-devel@...a-project.org,
        Timur Tabi <timur@...i.org>, Xiubo.Lee@...il.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Takashi Iwai <tiwai@...e.com>, fabio.estevam@....com,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [alsa-devel] [PATCH v3 2/2] ASoC: imx-wm8962: Fix codec_clk cleanup

On Tue, Mar 28, 2017 at 12:21 PM, Charles Keepax
<ckeepax@...nsource.wolfsonmicro.com> wrote:
> On Tue, Mar 28, 2017 at 11:58:52AM +0300, Daniel Baluta wrote:
>> Resource managed devm_clk_get only works with platform's device dev.
>>
>
> I feel like this could use an explaination of why not using devm
> is the correct fix, rather than just using the platform device
> for the call. Its not obvious to me, that using the platform
> device would be an issue.

Hi Charles,

I see where the confusion comes from :) and I thought the explanation
is obvious from the code, see inline comments.

Would an explanation like the one below, work better?

" We cannot use devm_clk_get with &codec_dev->dev device because
the kernel uses pdev->dev to free the managed resources, so we will end
up with a leaking codec_clk reference"

>> @@ -231,7 +231,7 @@ static int imx_wm8962_probe(struct platform_device *pdev)
>>               goto fail;
>>       }

pdev->dev from here:

>>
>> -     codec_clk = devm_clk_get(&codec_dev->dev, NULL);
>> +     codec_clk = clk_get(&codec_dev->dev, NULL);

is different from &codec_dev->dev.

>>       if (IS_ERR(codec_clk)) {
>>               ret = PTR_ERR(codec_clk);
>>               dev_err(&codec_dev->dev, "failed to get codec clk: %d\n", ret);
>> @@ -239,6 +239,7 @@ static int imx_wm8962_probe(struct platform_device *pdev)
>>       }
>>
>>       data->clk_frequency = clk_get_rate(codec_clk);
>> +     clk_put(codec_clk);
>>
>>       data->dai.name = "HiFi";
>>       data->dai.stream_name = "HiFi";

thanks,
Daniel.