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

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Date: Tue, 9 Jan 2024 13:04:52 +0000
From: Conor Dooley <conor.dooley@...rochip.com>
To: 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

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.

> 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?

Cheers,
Conor.

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