Re: [PATCH] arm64: dts: imx95: remove CLK_GPUAPB

[Marek Vasut <marek.vasut@mailbox.org>]

On 1/1/26 1:37 AM, Rain Yang wrote:
> On Wed, Dec 31, 2025 at 03:11:21PM +0100, Marek Vasut wrote:
>> On 12/31/25 4:19 AM, Rain Yang wrote:
>>> From: Rain Yang <jiyu.yang@nxp.com>
>>>
>>> Dropping CLK_GPUAPB simplifies OPP handling and avoids unnecessary
>>> complexity.
>>>
>>> Fixes: 67934f248e64 ("arm64: dts: imx95: Describe Mali G310 GPU")
>>> Signed-off-by: Rain Yang <jiyu.yang@nxp.com>
>>> ---
>>>    arch/arm64/boot/dts/freescale/imx95.dtsi | 4 ++--
>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm64/boot/dts/freescale/imx95.dtsi b/arch/arm64/boot/dts/freescale/imx95.dtsi
>>> index 88bde59e61b2..ab446aa6f73c 100644
>>> --- a/arch/arm64/boot/dts/freescale/imx95.dtsi
>>> +++ b/arch/arm64/boot/dts/freescale/imx95.dtsi
>>> @@ -2164,8 +2164,8 @@ netc_emdio: mdio@0,0 {
>>>    		gpu: gpu@4d900000 {
>>>    			compatible = "nxp,imx95-mali", "arm,mali-valhall-csf";
>>>    			reg = <0 0x4d900000 0 0x480000>;
>>> -			clocks = <&scmi_clk IMX95_CLK_GPU_CGC>, <&scmi_clk IMX95_CLK_GPUAPB>;
>>> -			clock-names = "core", "coregroup";
>>> +			clocks = <&scmi_clk IMX95_CLK_GPU_CGC>;
>>> +			clock-names = "core";
>>
>> I don't think this is correct, SM can disable the GPUAPB clock from the SM
>> monitor:
>>
>>> $ clock.w gpuapb off
>>
>> Linux has to make sure the GPUAPB clock are enabled to access the GPU
>> register, hence the clock have to be described in DT.
> Hi Marek,

Hello Jiyu,

> CLK_GPU and CLK_GPUAPB can only be controlled internally by the SM, not by Linux.
> CLK_GPUAPB always runs at a fixed frequency, does not require dynamic adjustment,
> and is practically always on.
> Additionally, CLK_GPUAPB's frequency is absent from all OPP entries. Removing it
> could simplify OPP handling logic and reduce unnecessary complexity.

But the SM can turn the GPUAPB clock off, correct ?

Linux has to be able to turn GPUAPB clock on, therefore the GPUAPB clock 
have to be described in DT, correct ?