Re: [PATCH v2 4/9] drm/panthor: Implement optional reset

Marek Vasut
2025-09-04T14:54:54Z

On 9/4/25 4:04 PM, Boris Brezillon wrote:

Hello Boris,

>>>> I suspect the extra soft reset I did before "un-halted" the GPU and
>>>> allowed it to proceed.
>>>
>>> Hm, not quite. I mean, you still need to explicitly boot the MCU after
>>> a reset, which is what the write to MCU_CONTROL [1] does. What the
>>> soft-reset does though, is reset all GPU blocks, including the MCU.
>>> This means the MCU starts from a fresh state when you reach [1].
>>
>> I have a feeling the write to MCU_CONTROL does nothing in my case.
>
> I believe it does, otherwise you wouldn't be able to kick the MCU
> and get things working until the first runtime suspend happens. I gut
> feeling is that there's something fishy in the FW or SoC integration
> that causes the FW HALT request to put the MCU/GPU in a bad state
> preventing further MCU_CONTROL(AUTO_START) from functioning correctly
> after that point.

I wonder who at NXP could chime in ... Peng, do you know ?

>> Is there some way to probe the MCU state before/after setting GLB_HALT,
>> and also before/after the MCU_CONTROL write, using
>> gpu_read()/gpu_write() register operations, to find out what is going on
>> with the MCU at each point ?
>
> Yes, there's an MCU_STATUS register [1].
Is that the only register I can use , or is there something more
detailed ? This register only returns values 0..3 which is not very
informative.