linux-kernel - Re: [PATCH v3 6/8] riscv: dts: thead: Add GPU power sequencer node

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Message-ID: <c49ae9f2-3c3c-4253-be85-8fe5bbb4b42e@samsung.com>
Date: Tue, 3 Jun 2025 20:45:56 +0200
From: Michal Wilczynski <m.wilczynski@...sung.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Drew Fustini <drew@...7.com>, Guo Ren <guoren@...nel.org>, Fu Wei
	<wefu@...hat.com>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
	<krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Bartosz
	Golaszewski <brgl@...ev.pl>, Philipp Zabel <p.zabel@...gutronix.de>, Frank
	Binns <frank.binns@...tec.com>, Matt Coster <matt.coster@...tec.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
	<mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Paul Walmsley
	<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
	<aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>, Ulf Hansson
	<ulf.hansson@...aro.org>, Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 6/8] riscv: dts: thead: Add GPU power sequencer node



On 6/3/25 15:22, Krzysztof Kozlowski wrote:
> On Fri, May 30, 2025 at 12:23:53AM GMT, Michal Wilczynski wrote:
>> Add the device tree node for the T-HEAD TH1520 GPU power sequencer
>> (gpu_pwrseq) to the th1520.dtsi file.
>>
>> This node instantiates the thead,th1520-gpu-pwrseq driver, which
> 
> Explain the hardware, not what drivers do.
> 
>> is responsible for managing the GPU's power-on/off sequence. The node
>> specifies the gpu-clkgen reset, which is one of the resources
>> controlled by this sequencer.
>>
>> Signed-off-by: Michal Wilczynski <m.wilczynski@...sung.com>
>> ---
>>  arch/riscv/boot/dts/thead/th1520.dtsi | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/riscv/boot/dts/thead/th1520.dtsi b/arch/riscv/boot/dts/thead/th1520.dtsi
>> index bdbb1b985b0b76cf669a9bf40c6ec37258329056..6170eec79e919b606a2046ac8f52db07e47ef441 100644
>> --- a/arch/riscv/boot/dts/thead/th1520.dtsi
>> +++ b/arch/riscv/boot/dts/thead/th1520.dtsi
>> @@ -238,6 +238,12 @@ aon: aon {
>>  		#power-domain-cells = <1>;
>>  	};
>>  
>> +	gpu_pwrseq: pwrseq {
> 
> Node names should be generic. See also an explanation and list of
> examples (not exhaustive) in DT specification:
> https://protect2.fireeye.com/v1/url?k=a53ea5d3-c4434f50-a53f2e9c-74fe48600158-c81092475ef416b3&q=1&e=d333d06b-0b06-493e-a358-e29ca542dfe7&u=https%3A%2F%2Fdevicetree-specification.readthedocs.io%2Fen%2Flatest%2Fchapter2-devicetree-basics.html%23generic-names-recommendation
> 
>> +		compatible = "thead,th1520-gpu-pwrseq";
>> +		resets = <&rst TH1520_RESET_ID_GPU_CLKGEN>;
>> +		reset-names = "gpu-clkgen";
> 
> What is the point of pwrseq if there is no consumer/user of it? Looks
> like simple placeholder and anyway maybe the future consumer should just
> use reset directly.

Yeah I think you're right, I wanted to explore adding the pwrseq
provider in separate node per discussion in v2 [1]. But for the v4 I
think I'll revert to the v2 way of handling this reset [2].

[1] - https://lore.kernel.org/all/CAPDyKFpi6_CD++a9sbGBvJCuBSQS6YcpNttkRQhQMTWy1yyrRg@mail.gmail.com/
[2] - https://lore.kernel.org/all/20250414-apr_14_for_sending-v2-2-70c5af2af96c@samsung.com/

> 
> Best regards,
> Krzysztof
> 
> 

Best regards,
-- 
Michal Wilczynski <m.wilczynski@...sung.com>