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From: Daniel Baluta <daniel.baluta@gmail.com>
Date: Wed, 29 Mar 2017 14:38:23 +0300
Message-ID: <CAEnQRZCiaCfzQRDo-3UupH8fv9BttZBVVXo63FdnrdqG49F1GQ@mail.gmail.com>
Subject: Re: [alsa-devel] [PATCH v3 2/2] ASoC: imx-wm8962: Fix codec_clk cleanup
To: Mark Brown <broonie@kernel.org>
Cc: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>,
        Daniel Baluta <daniel.baluta@nxp.com>,
        Nicolin Chen <nicoleotsuka@gmail.com>, alsa-devel@alsa-project.org,
        Timur Tabi <timur@tabi.org>, Xiubo.Lee@gmail.com,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>, Takashi Iwai <tiwai@suse.com>,
        fabio.estevam@nxp.com, linuxppc-dev@lists.ozlabs.org
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On Tue, Mar 28, 2017 at 6:24 PM, Mark Brown <broonie@kernel.org> wrote:
> On Tue, Mar 28, 2017 at 12:53:06PM +0100, Charles Keepax wrote:
>> On Tue, Mar 28, 2017 at 01:47:04PM +0300, Daniel Baluta wrote:
>
>> > >> -     codec_clk = devm_clk_get(&codec_dev->dev, NULL);
>> > >> +     codec_clk = clk_get(&codec_dev->dev, NULL);
>
>> > is different from &codec_dev->dev.
>
>> I get that they are different, I just don't get why changing
>> from a devm_clk_get to a clk_get is a better fix than changing
>> &codec->dev to &pdev->dev.
>
> This should be clear from the semantics of clk_get(): you're looking up
> the clock in the context of the supplied device and the clock is
> attached to the CODEC so you need to look up in the CODEC context.  What
> would be even better would be to move the allocation of the clock into
> the CODEC driver...

If I read the code correctly, both machine and codec driver are doing:

* codec_clk = clk_get(...)

I guess that the codec driver is the first to be loaded and it will call:

* __clk_create_clk

which will do the allocation. Then when machine driver is loaded, it
will only take a reference to the allocated clock.

I might be very wrong on this. Can you clarify what does moving allocation
of the clock into codec driver implies? Machine driver only needs a reference
to codec_clk to just get the clock's rate.

Daniel.