linux-kernel - Re: [PATCH v2] ASoC: da7219: read fmw property to get mclk for non-dts systems

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Message-ID: <20180503013919.GN2714@sirena.org.uk>
Date:   Thu, 3 May 2018 10:39:19 +0900
From:   Mark Brown <broonie@...nel.org>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     Akshu Agrawal <akshu.agrawal@....com>,
        "djkurtz@...omium.org" <djkurtz@...omium.org>,
        "Alexander.Deucher@....com" <Alexander.Deucher@....com>,
        Support Opensource <Support.Opensource@...semi.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        "moderated list:SOUND" <alsa-devel@...a-project.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ASoC: da7219: read fmw property to get mclk for
 non-dts systems

On Wed, May 02, 2018 at 10:13:55AM +0000, Adam Thomson wrote:
> On 01 May 2018 21:50, Mark Brown wrote:

> > There's a lot of things that ACPI *should* do but doesn't - it's a bit
> > of a shambles how ACPI standards get defined and what's there is not
> > really intended to handle systems like these semi-embedded ones.  One of
> > the big gaps in ACPI is that it has no handling at all of clocks, that's
> > supposed to be done transparently by firmware in the ACPI model.  What a
> > lot of the embedded Intel people have been doing is coopting the DT
> > bindings wholesale for ACPI systems but that has problems when you get
> > into areas which should be handled in some way on ACPI systems like
> > power and unfortunately clocks are kind of power adjacent so might be a
> > bit sketchy here.

> Yes I was aware that previously that was the case, although have not followed
> this for a while. It just feels here that we should aim for something more
> generic rather than a device specific property/binding, if possible, as that
> feels messy to me and I'm sure other drivers could take advantage of this as
> well. I've not looked at the clock code in too much detail though, at least with
> regards to this area, so not sure how feasible that is.

> As a suggestion for ACPI would it be possible to re-use the 'clock-names'
> property and add something in the framework to handle this?

I completely agree that ACPI should have handling for clocks but it
really feels like something that should be done as a proper spec rather
than just ad hoc by Linux like the x86 embedded people often do - it's
too close to the power management stuff that ACPI definitely does
handle.

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