linux-kernel - Re: [PATCH v2 2/2] arm64: dts: ti: k3-j721s2: Add GPU node

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Message-ID: <20250422120420.iv2hbaf4ykqazvlx@bleak>
Date: Tue, 22 Apr 2025 07:04:20 -0500
From: Nishanth Menon <nm@...com>
To: Randolph Sapp <rs@...com>
CC: "Kumar, Udit" <u-kumar1@...com>, Matt Coster <matt.coster@...tec.com>,
        Vignesh Raghavendra <vigneshr@...com>, Tero Kristo <kristo@...nel.org>,
        Rob
 Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor
 Dooley <conor+dt@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Frank Binns
	<frank.binns@...tec.com>,
        Alessio Belle <alessio.belle@...tec.com>,
        Alexandru
 Dadu <alexandru.dadu@...tec.com>,
        Luigi Santivetti
	<luigi.santivetti@...tec.com>,
        Darren Etheridge <detheridge@...com>
Subject: Re: [PATCH v2 2/2] arm64: dts: ti: k3-j721s2: Add GPU node

On 18:51-20250421, Randolph Sapp wrote:
> On Sat Apr 19, 2025 at 11:15 AM CDT, Udit Kumar wrote:
> > Hello Matt,
> >
> > On 4/17/2025 2:40 PM, Matt Coster wrote:
> >> The J721S2 binding is based on the TI downstream binding in commit
> >> 54b0f2a00d92 ("arm64: dts: ti: k3-j721s2-main: add gpu node") from [1]
> >> but with updated compatible strings.
> >
> > Downstream kernel[1] sha 5657fc069e8b3 ("PENDING: arm64: dts: ti: 
> > k3-j721s2-main: add gpu node")
> >
> > also has assigned-clock-rates.
> >
> > Please check if gpu node needs assigned-rate too.
> 
> If I remember correctly, J721S2 was one of the few platforms that actually
> defaulted to 800MHz, so it may not be necessary for that platform specifically.
> (I don't have a board to test this right now though. This very well may have
> changed.) AM62 also defaults to the correct value, and that one I did manage to
> verify.
> 
> That being said, Udit is right, it's generally a good idea to explicitly set the
> clock speed for our devices. I know AM62P, for example, used to default our
> clock to the bus speed.
> 
> At one point though this driver was experimenting with a DVFS mechanism. Matt,
> use of assigned-clocks shouldn't interfere with that assuming there is no
> defined opp-table, right? May be a good idea to set our usual 800 MHz for J721S2
> and 500 MHz for AM625. This shouldn't require any binding related changes.
> 
> On the topic of opp tables for the GPU, I did some testing on the proprietary
> driver a little while back. These devices do not support voltage scaling and
> simple frequency scaling saw a general decrease in performance and increase in
> power draw for the usual utilization bursts a single application running at 60
> FPS generates. I have a feeling this will carry over to the open source driver,
> but we can always do additional testing if you are curious.
> 
> - Randolph
> 
> >> The clock[2] and power[3] indices were verified from HTML docs, while
> >> the intterupt index comes from the TRM[4] (appendix
> >> "J721S2_Appendix_20241106_Public.xlsx", "Interrupts (inputs)",
> >> "GPU_BXS464_WRAP0_GPU_SS_0_OS_IRQ_OUT_0").
> >
> >> [1]: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel
> >> [2]: https://downloads.ti.com/tisci/esd/latest/5_soc_doc/j721s2/clocks.html
> >> [3]: https://downloads.ti.com/tisci/esd/latest/5_soc_doc/j721s2/devices.html
> >> [4]: https://www.ti.com/lit/zip/spruj28 (revision E)
> >>
> >> Reviewed-by: Randolph Sapp <rs@...com>
> >> Signed-off-by: Matt Coster <matt.coster@...tec.com>
> >> ---
> >> Changes in v2:
> >> - Add interrupt reference details
> >> - Add Randolph's Rb
> >> - Link to v1: https://lore.kernel.org/r/20250415-bxs-4-64-dts-v1-2-f7d3fa06625d@imgtec.com
> >>
> >> This patch was previously sent as [DO NOT MERGE]:
> >> https://lore.kernel.org/r/20250410-sets-bxs-4-64-patch-v1-v6-18-eda620c5865f@imgtec.com
> >> ---
> >>   arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi | 12 ++++++++++++
> >>   1 file changed, 12 insertions(+)
> >>
> >> diff --git a/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi b/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi
> >> index 92bf48fdbeba45ecca8c854db5f72fd3666239c5..a79ac41b2c1f51b7193e6133864428bd35a5e835 100644
> >> --- a/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi
> >> +++ b/arch/arm64/boot/dts/ti/k3-j721s2-main.dtsi
> >> @@ -2048,4 +2048,16 @@ watchdog8: watchdog@...0000 {
> >>   		/* reserved for MAIN_R5F1_1 */
> >>   		status = "reserved";
> >>   	};
> >> +
> >> +	gpu: gpu@...0000000 {
> >> +		compatible = "ti,j721s2-gpu", "img,img-bxs-4-64", "img,img-rogue";
> >> +		reg = <0x4e 0x20000000 0x00 0x80000>;
> >> +		clocks = <&k3_clks 130 1>;

On the basis of the above discussion, Matt,
please add:
assigned-clocks = <&k3_clks 130 1>;
assigned-clock-rates = <800000000>;

> >> +		clock-names = "core";
> >> +		interrupts = <GIC_SPI 24 IRQ_TYPE_LEVEL_HIGH>;
> >> +		power-domains = <&k3_pds 130 TI_SCI_PD_EXCLUSIVE>,
> >> +				<&k3_pds 373 TI_SCI_PD_EXCLUSIVE>;
> >> +		power-domain-names = "a", "b";
> >> +		dma-coherent;
> >> +	};
> >>   };
> >>
> 

-- 
Regards,
Nishanth Menon
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