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

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 4 Sep 2025 16:54:38 +0200
Marek Vasut <marek.vasut@mailbox.org> wrote:

> 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.

Not that I'm aware.