linux-kernel - Re: [PATCH v3 10/12] dt-bindings: mediatek: mt8188: add audio afe document

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Date:   Tue, 13 Dec 2022 15:06:03 +0000
From:   Trevor Wu (吳文良) <Trevor.Wu@...iatek.com>
To:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "perex@...ex.cz" <perex@...ex.cz>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 10/12] dt-bindings: mediatek: mt8188: add audio afe
 document

On Mon, 2022-12-12 at 09:40 +0100, Krzysztof Kozlowski wrote:
> On 12/12/2022 03:43, Trevor Wu (吳文良) wrote:
> > > > 
> > > > > > +    uniqueItems: true
> > > > > > +    items:
> > > > > > +      minimum: 0
> > > > > > +      maximum: 15
> > > > > > +
> > > > > > +  "^mediatek,etdm-in[1-2]-mclk-always-on-rate-hz$":
> > > > > > +    description: Specify etdm in mclk output rate for
> > > > > > always
> > > > > > on
> > > > > > case.
> > > > > 
> > > > > How is it different than assigned-clock-rates?
> > > > > 
> > > > 
> > > > This includes clock enabling at init stage.
> > > 
> > > assigned-clock-rates are also at init stage. I asked what is
> > > different.
> > > 
> > 
> > If the property is used, there are three parts included in dai
> > driver
> > probe function.
> > 
> > 1. set clock parent (which APLL)
> > 2. set clock rate (MCLK rate)
> > 3. enable clock (MCLK On)
> > 
> > The first two parts can be done by existing dts clock properties,
> > but
> > the last one can't.
> > When MCLK should be enabled at boot time and kept on, this property
> > is used. That's why I say the property is designed for always-on
> > case.
> 
> Heh, so the "always on case" means this property enables clock? How
> is
> this even DT property? That's not how clocks should be kept enabled.
> You
> need proper clock provider and consumer.
> 
> 

Hi Krzysztof,

Sorry, I don't know it is not appropriate to notify driver that the
clock should be ketp enabled after boot.

The original idea is that enabling this clock in the machine driver,
but a property to inform machine driver is also required when the
machine driver is shared by different codec combination. And it's
easier to handle set_rate and set_parent in etdm dai driver, so I put
the property here.

Do you mean if the clock consumer(audio codec or external DSP) requries
the clock, the consumer should enable the clock by itself?

Thanks,
Trevor