Re: [PATCH v5 3/3] arm64: dts: qcom: sm8750: Add GPU clock & IOMMU nodes

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 3/12/26 7:40 AM, Pengyu Luo wrote:
> On Tue, Mar 10, 2026 at 9:32 PM Konrad Dybcio
> <konrad.dybcio@oss.qualcomm.com> wrote:
>>
>> On 3/9/26 11:27 AM, Pengyu Luo wrote:
>>> On Thu, Mar 5, 2026 6:40 PM Taniya Das <taniya.das@oss.qualcomm.com> wrote:
>>>> From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>>>>
>>>> Add the GPU_CC and GX_CC (brand new! as far as we're concerned, this
>>>> is simply a separate block housing the GX GDSC) nodes, required to
>>>> power up the graphics-related hardware.
>>>>
>>>> Make use of it by enabling the associated IOMMU as well. The GPU itself
>>>> needs some more work and will be enabled later.
>>>>
>>>> Reviewed-by: Abel Vesa <abel.vesa@oss.qualcomm.com>
>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>>>> Co-developed-by: Taniya Das <taniya.das@oss.qualcomm.com>
>>>> Signed-off-by: Taniya Das <taniya.das@oss.qualcomm.com>
>>>> ---
>>>>
>>>
>>> Hi Taniya and Konrad, GX GDSC stuck at 'on' on my device
>>> the raw register values are
>>>
>>> 0x3d68024: 0x00000000
>>> 0x3d68028: 0x00000000
>>
>> These likely indicate that some clock or voltage rail is not accessible
>> at the very moment you're reading them back
>>
> 
> It seems to be harmless. In the downstream, they are always zero too.
> TB322FC:/ # devmem 0x3d68024
> 0x00000000
> TB322FC:/ # devmem 0x3d68028
> 0x00000000
> 
> In [1], the commit log mentioned
> The GX GDSC is modelled to aid the GMU in powering down the GPU in the
> event that the GPU crashes.
> 
>> GPU support for 8750 is not yet upstream (and A830 is somewhat different
>> vs the supported A840) - there may be something wrong in that sequence.
>>
> 
> Indeed. Chances are that I can't enable gpu. I must reboot again and again to
> match the sequence by luck, then I can enable it[2], and I must
> disable register protection.(I just noticed the hack from here[3])
> 
>> I heard it's in the works though, so you may be better off waiting a bit.
>>
> 
> Glad to hear that. I am looking forward to it.
> 
> Slightly off-topic, do you know if anyone is working on wcn786x/wcn7880,
> sm8750 QRD SKU2 V8 Power Grid uses this.

I don't know. You can try asking on ath12k@lists.infradead.org

Konrad