Re: [PATCH v3 3/6] arm64: dts: qcom: kodiak: Add GEM_NOC interconnect for adreno SMMU

[Bibek Kumar Patro <bibek.patro@oss.qualcomm.com>]

On 7/7/2026 10:14 PM, Dmitry Baryshkov wrote:
> On Tue, Jul 07, 2026 at 06:37:24PM +0530, Bibek Kumar Patro wrote:
>>
>>
>> On 7/6/2026 11:12 PM, Dmitry Baryshkov wrote:
>>> On Mon, Jul 06, 2026 at 10:26:36PM +0530, Bibek Kumar Patro wrote:
>>>> On Kodiak platforms, the Adreno SMMU requires a bandwidth vote on
>>>> the GEM_NOC path (MASTER_GPU_TCU -> SLAVE_EBI1) before its registers
>>>> are accessible. Without this vote, the SMMU may become unreachable,
>>>> leading to intermittent probe failures and runtime issues.
>>>>
>>>> Add the required interconnect to ensure reliable register access.
>>>>
>>>> Signed-off-by: Bibek Kumar Patro <bibek.patro@oss.qualcomm.com>
>>>> ---
>>>>    arch/arm64/boot/dts/qcom/kodiak.dtsi | 2 ++
>>>>    1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/qcom/kodiak.dtsi b/arch/arm64/boot/dts/qcom/kodiak.dtsi
>>>> index 90e50c245c0c..721526f023dd 100644
>>>> --- a/arch/arm64/boot/dts/qcom/kodiak.dtsi
>>>> +++ b/arch/arm64/boot/dts/qcom/kodiak.dtsi
>>>> @@ -3389,6 +3389,8 @@ adreno_smmu: iommu@3da0000 {
>>>>    			power-domains = <&gpucc GPU_CC_CX_GDSC>;
>>>>    			dma-coherent;
>>>> +			interconnects = <&gem_noc MASTER_GPU_TCU QCOM_ICC_TAG_ALWAYS
>>>> +					 &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>;
>>>
>>> Why is it ALWAYS? Would it be better to declare it as ACTIVE_ONLY and
>>
>> Added QCOM_ICC_TAG_ALWAYS, to hold the vote in SLEEP bucket as well
>> preventing gem_noc going to sleep when icc_set_bw is being called.
> 
> _why_?
> 

Now when i think of where we implemented the hooks, ALWAYS is not 
needed. We should keep it ACTIVE_ONLY since we are already voting it
back in resume pah. I'll fix it in next revision.

>>
>>> then drop the extra suspend/resume play?
>>
>> Not sure if I understood it correctly.
>> Did you mean the extra suspend/resume play in arm_smmu_runtime_suspend
>> or in arm_smmu_device_shutdown() path?
> 
> runtime_suspend/resume. I might be incorrect here, but I think it is
> exactly what you need.
> 

Yes, I think we should go with the ACTIVE_ONLY flag and we would need
this voting in suspend resume path (For the same reason mentioned in 
commit description and cover letter of the series).

ALWAYS would avoid the need for this handling, it would keep the vote 
active unnecessarily, but still that would have been nondeterministic.

Thanks & regards,
Bibek

>>
>> Thanks & regards,
>> Bibek
>>
>>>
>>>>    		};
>>>>    		gfx_0_tbu: tbu@3dd9000 {
>>>>
>>>> -- 
>>>> 2.34.1
>>>>
>>>
>>
>