linux-kernel - Re: [PATCH v2 3/8] riscv: dts: thead: Add TH1520 pin control nodes

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Date: Tue, 9 Jan 2024 06:28:19 -0800
From: Emil Renner Berthing <emil.renner.berthing@...onical.com>
To: Conor Dooley <conor.dooley@...rochip.com>, 
	Emil Renner Berthing <emil.renner.berthing@...onical.com>
Cc: Conor Dooley <conor@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-riscv@...ts.infradead.org, Linus Walleij <linus.walleij@...aro.org>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Jisheng Zhang <jszhang@...nel.org>, Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Drew Fustini <dfustini@...libre.com>
Subject: Re: [PATCH v2 3/8] riscv: dts: thead: Add TH1520 pin control nodes

Conor Dooley wrote:
> On Tue, Jan 09, 2024 at 04:02:01AM -0800, Emil Renner Berthing wrote:
> > Conor Dooley wrote:
> > > On Wed, Jan 03, 2024 at 02:28:40PM +0100, Emil Renner Berthing wrote:
> > > > Add nodes for pin controllers on the T-Head TH1520 RISC-V SoC.
> > > >
> > > > Signed-off-by: Emil Renner Berthing <emil.renner.berthing@...onical.com>
> > > > ---
> > > >  .../boot/dts/thead/th1520-beaglev-ahead.dts   |  4 ++++
> > > >  .../dts/thead/th1520-lichee-module-4a.dtsi    |  4 ++++
> > > >  arch/riscv/boot/dts/thead/th1520.dtsi         | 24 +++++++++++++++++++
> > > >  3 files changed, 32 insertions(+)
> > > >
> > > > diff --git a/arch/riscv/boot/dts/thead/th1520-beaglev-ahead.dts b/arch/riscv/boot/dts/thead/th1520-beaglev-ahead.dts
> > > > index 70e8042c8304..6c56318a8705 100644
> > > > --- a/arch/riscv/boot/dts/thead/th1520-beaglev-ahead.dts
> > > > +++ b/arch/riscv/boot/dts/thead/th1520-beaglev-ahead.dts
> > > > @@ -44,6 +44,10 @@ &osc_32k {
> > > >  	clock-frequency = <32768>;
> > > >  };
> > > >
> > > > +&aonsys_clk {
> > > > +	clock-frequency = <73728000>;
> > > > +};
> > > > +
> > > >  &apb_clk {
> > > >  	clock-frequency = <62500000>;
> > > >  };
> > > > diff --git a/arch/riscv/boot/dts/thead/th1520-lichee-module-4a.dtsi b/arch/riscv/boot/dts/thead/th1520-lichee-module-4a.dtsi
> > > > index a802ab110429..9865925be372 100644
> > > > --- a/arch/riscv/boot/dts/thead/th1520-lichee-module-4a.dtsi
> > > > +++ b/arch/riscv/boot/dts/thead/th1520-lichee-module-4a.dtsi
> > > > @@ -25,6 +25,10 @@ &osc_32k {
> > > >  	clock-frequency = <32768>;
> > > >  };
> > > >
> > > > +&aonsys_clk {
> > > > +	clock-frequency = <73728000>;
> > > > +};
> > > > +
> > > >  &apb_clk {
> > > >  	clock-frequency = <62500000>;
> > > >  };
> > > > diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
> > > > index ba4d2c673ac8..e65a306ff575 100644
> > > > --- a/arch/riscv/boot/dts/thead/th1520.dtsi
> > > > +++ b/arch/riscv/boot/dts/thead/th1520.dtsi
> > > > @@ -134,6 +134,12 @@ osc_32k: 32k-oscillator {
> > > >  		#clock-cells = <0>;
> > > >  	};
> > > >
> > > > +	aonsys_clk: aonsys-clk {
> > > > +		compatible = "fixed-clock";
> > > > +		clock-output-names = "aonsys_clk";
> > > > +		#clock-cells = <0>;
> > > > +	};
> > >
> > > Did this stuff sneak into this commit accidentally?
> >
> > Not really by accident no. It turns out the clock tree has gates for the bus
> > clock of each pinctrl block and I think it's better to add this clock
> > dependency to the bindings and driver up front.
>
> Maybe if I had looked a wee bit more deeply I would've noticed that it
> was used there, but it's always good to mention the rationale in the
> commit message so that it's more obvious why you're doin it.

You absolutely right. I forgot to update the commit message.

> > Since there is not yet any clock driver the initial device tree for the TH1520
> > included the dummy apb_clk that two of the pinctrl blocks derive their clock
> > from, but not the "aonsys" clock needed by the "always-on" pinctrl. I thought
> > it was better to add this dummy clock with the only (so far) user of it, but if
> > you have a better idea, let me know.
>
> No, that's fine. I was just wondering why there was an unmentioned set
> of clocks being added. If they're stubbed fixed clocks I dunno if it
> makes sense to add them to the board.dts/module.dtsi files though. Where
> do the initial values come from for the rates? Out of reset values or
> set by firmware that may vary from board to board?

The vendor u-boot sets the PLLs different from the reset values. For now I
think it's the same code for every board using the Lichee Pi 4A module (and
probably also for the BeagleV Ahead), but it might still make sense to move the
freqency to the board instead of the module device tree.

/Emil