Re: [PATCH v2 2/7] media: iris: switch to hardware mode after firmware boot

[Konrad Dybcio]

On 3/3/26 7:15 PM, Vikash Garodia wrote:
> 
> 
> On 2/27/2026 10:19 PM, Konrad Dybcio wrote:
>> On 2/27/26 3:11 PM, Vikash Garodia wrote:
>>> Currently the driver switches the vcodec GDSC to hardware (HW) mode
>>> before firmware load and boot sequence. GDSC can be powered off, keeping
>>> in hw mode, thereby the vcodec registers programmed in TrustZone (TZ)
>>> carry default (reset) values.
>>> Move the transition to HW mode after firmware load and boot sequence.
>>>
>>> The bug was exposed with driver configuring different stream ids to
>>> different devices via iommu-map. With registers carrying reset values,
>>> VPU would not generate desired stream-id, thereby leading to SMMU fault.
>>>
>>> For vpu4, when GDSC is switched to HW mode, there is a need to perform
>>> the reset operation. Without reset, there are occassional issues of
>>> register corruption observed. Hence the vpu GDSC switch also involves
>>> the reset.
>>
>> Is that a characteristic of the hardware (e.g. also seen downstream), or
>> is that required with upstream iris only?
> 
> it was found lately with one of vpu4 variant SOC and applicable for all vpu4s.

Thanks

Konrad