Re: [PATCH] arm64: dts: imx95: Use GPU_CGC as core clock for GPU

[Rain Yang <jiyu.yang@oss.nxp.com>]

On Wed, Dec 03, 2025 at 11:48:47PM +0100, Marek Vasut wrote:
>On 12/3/25 10:28 AM, Rain Yang wrote:
>
>Hello Rain,
>
>> > > Thanks for integrating this downstream patch.
>> > 
>> > Which downstream patch do you refer to ?
>> > 
>> > > Please note that CLK_GPUAPB and CLK_GPU are
>> > > always-on, so the commit message should be amended accordingly.
>> > 
>> > The GPU clock do not seem to be always-on, neither do the GPUAPB . It seems
>> > the SM can turn those clock off perfectly well.
>> > 
>> > > Additionally, the IMX95_CLK_GPUAPB handle shall be removed, as there is no valid OPP entry
>> > > in the frequency table, this also helps minimize differences between downstream and upstream,
>> > > reducing maintenance effort.
>> > 
>> > Downstream kernel forks are not relevant to this discussion, upstream your
>> > content and then you won't have to spend maintenance effort on downstream
>> > stuff.
>> 
>> This patch [1] was the reference point.
>
>Sigh ... I was not aware of that one.
>
>Maybe next time, it would be good to upstream these changes directly ?
>
>> For the Linux working environment,
>> CLK_GPU and CLK_GPUAPB are always-on, while CLK_GPU_CGC can be gated off.
>> 
>> Regarding the IMX95_CLK_GPUAPB handle, my suggestion was based on the absence
>> of its frequency in any OPP entry within the frequency table. Removing it
>> could simplify the OPP handling logic and reduce unnecessary complexity.
>
>If the clock can be disabled by SM, Linux has to make sure they are NOT
>disabled, so they must be described in DT, right ?
>
>> [1] https://github.com/nxp-imx/linux-imx/commit/695f2bdc57b869ca5189313e4b5fa7eb5a12f622
Currently, only CLK_GPU_CGC shall be described in the Device Tree[1], as it can be gated.
The other clocks (CLK_GPU and CLK_GPUAPB) are always-on in the Linux environment,
so describing any of them in DT is not necessary and would not be proper in this context.
>
>
>-- 
>Best regards,
>Marek Vasut