linux-kernel - Re: [PATCH] arm64: dts: allwinner: a64: Move CPU OPPs to the SoC dtsi file

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Message-ID: <20240905134254.6e15a1e5@donnerap.manchester.arm.com>
Date: Thu, 5 Sep 2024 13:42:54 +0100
From: Andre Przywara <andre.przywara@....com>
To: Dragan Simic <dsimic@...jaro.org>
Cc: Chen-Yu Tsai <wens@...e.org>, linux-sunxi@...ts.linux.dev,
 jernej.skrabec@...il.com, samuel@...lland.org,
 linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
 robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: allwinner: a64: Move CPU OPPs to the SoC
 dtsi file

On Thu, 05 Sep 2024 14:38:53 +0200
Dragan Simic <dsimic@...jaro.org> wrote:

> Hello Andre,
> 
> On 2024-09-05 14:34, Andre Przywara wrote:
> > On Thu, 5 Sep 2024 20:26:15 +0800
> > Chen-Yu Tsai <wens@...e.org> wrote:
> >   
> >> Hi,
> >> 
> >> On Thu, Sep 5, 2024 at 8:17 PM Dragan Simic <dsimic@...jaro.org> 
> >> wrote:  
> >> >
> >> > Hello,
> >> >
> >> > Just checking, any further thoughts about this patch?  
> >> 
> >> Sorry, but I feel like it's not really worth the churn. There's not
> >> really a problem to be solved here. What you are arguing for is more
> >> about aesthetics, and we could argue that having them separate makes
> >> it easier to read and turn on/off.  
> > 
> > Yeah, I agree. If a board wants to support OPPs, they just have to 
> > include
> > a single file and define the CPU regulator, and that's a nice opt-in,
> > IMHO.
> > But having this patch would make it quite hard to opt out, I believe. 
> > For
> > Linux there are probably ways to disable DVFS nevertheless, but I am 
> > not
> > sure this is true in an OS agnostic pure-DT-only way.  
> 
> Thanks for your response.  The only thing that still makes me wonder
> is why would a board want to opt out of DVFS?  Frankly, I'd consider
> the design of the boards that must keep DVFS disabled broken.

Yes! Among the boards using Allwinner SoCs there are some, say less-optimal
designs ;-)

Cheers,
Andre

> > This could probably be solved, but same as Chen-Yu I don't see any good
> > enough reason for this patch in the first place.
> >   
> >> And even though the GPU OPPs are in the dtsi, it's just one OPP acting
> >> as a default clock rate.