Re: [PATCH 0/3] drm/panthor: Misc MMU fixes/robustness improvements

[Liviu Dudau]

On Thu, Sep 24, 2026 at 02:30:42PM +0200, Boris Brezillon wrote:
> The first commit is fixing a bug we've seen on v13 HW. Even though
> we don't quite understand what happens (race in the flush-elimination
> logic when flush requests are sent concurrently from the CPU and the
> MCU), it seems that the downstream driver has always been doing a
> flush+invalidate of RW caches from the start, and that we were doing
> so up until the atomic page table update changes, so let's go back to
> that state and leave the RO L1 caches untouched.
> 
> The second patch a fix for a race that could very well happen if we
> ever end up with a failure between the as_disable() and as_enable()
> calls. We've not experienced this so far, but it seems worth plugging
> the hole regardless. The last patch is a much more theoretical bug,
> which would involve a buggy FW telling us that a CSG is suspended,
> when it's actually. I've deliberately not added a Fixes tag on the
> last one for this very reason, but I think it's worth staying on
> the safe side by addressing this theoretical issue, still.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> ---
> Boris Brezillon (3):
>       drm/panthor: Don't invalidate OTHER caches
>       drm/panthor: Fully disable the AS even if it's going to be re-assigned
>       drm/panthor: Move cache-flush after UPDATE(UNMAPPED)
> 
>  drivers/gpu/drm/panthor/panthor_mmu.c | 43 ++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 23 deletions(-)
> ---
> base-commit: 45585c3aa285854face65293acc95eff73063d6d
> change-id: 20260924-panthor-mmu-fixes-a1832dc60908
> 
> Best regards,
> --  
> Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> 

Pushed the whole series into drm-misc-next-fixes after updating the comment
on 1/3 as suggested by sashiko.

Best regards,
Liviu

-- 
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