linux-kernel - Re: [PATCH 1/5] riscv: dts: allwinner: Update opp table to allow CPU frequency scaling

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Message-ID: <2177637.Mh6RI2rZIc@archlinux>
Date:   Thu, 14 Dec 2023 17:36:59 +0100
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Conor Dooley <conor@...nel.org>
Cc:     Brandon Cheo Fusi <fusibrandon13@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Samuel Holland <samuel@...lland.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Yangtao Li <tiny.windzz@...il.com>, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 1/5] riscv: dts: allwinner: Update opp table to allow CPU
 frequency scaling

On Thursday, December 14, 2023 2:47:14 PM CET Conor Dooley wrote:
> On Thu, Dec 14, 2023 at 04:44:46PM +0530, Viresh Kumar wrote:
> > On 14-12-23, 11:33, Brandon Cheo Fusi wrote:
> > > Two OPPs are currently defined for the D1/D1s; one at 408MHz and
> > > another at 1.08GHz. Switching between these can be done with the
> > > "sun50i-cpufreq-nvmem" driver. This patch populates the opp table
> > > appropriately, with inspiration from
> > > https://github.com/Tina-Linux/linux-5.4/blob/master/arch/riscv/boot/dts/sunxi/sun20iw1p1.dtsi
> > > 
> > > The supply voltages are PWM-controlled, but support for that IP
> > > is still in the works. So stick to a fixed 0.9V vdd-cpu supply,
> > > which seems to be the default on most D1 boards.
> > > 
> > > Signed-off-by: Brandon Cheo Fusi <fusibrandon13@...il.com>
> > > ---
> > >  arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi | 18 +++++++++++++++---
> > >  1 file changed, 15 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi b/arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi
> > > index 64c3c2e6c..e211fe4c7 100644
> > > --- a/arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi
> > > +++ b/arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi
> > > @@ -39,16 +39,22 @@ cpu0_intc: interrupt-controller {
> > >  	};
> > >  
> > >  	opp_table_cpu: opp-table-cpu {
> > > -		compatible = "operating-points-v2";
> > > +		compatible = "allwinner,sun20i-d1-operating-points",
> > 
> > I don't think you should add a new compatible for every SoC that needs
> > to be supported by a DT bindings and cpufreq driver. Maybe you should
> > just reuse "allwinner,sun50i-h6-operating-points" and it will work
> > fine for you ?
> > 
> > Rob ?
> 
> The driver can definitely just reuse sun50i-h6, but the binding and
> devicetree should have a soc-specific compatible for the sun20i-d1.

Correct. This is to avoid later regrets if it turns out there are some slight
differences or additional functionality.

Best regards,
Jernej

> 
> That said, the compatible does need to be documented, there's a
> dt-bindings patch missing from this series.
> 
> Cheers,
> Conor.