Re: [PATCH v7 14/17] drm/panfrost: Avoid cache flush after perfcnt sample in fully coherent systems

[Boris Brezillon]

On Fri, 28 Aug 2026 21:56:54 +0100
Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx> wrote:

> If the GPU and CPU are fully coherent, then there's no need to flush the
> GPU caches after a perfcnt sample is made available.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/panfrost/panfrost_perfcnt.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> index ffc77121070e..b3f71d7fd82a 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_perfcnt.c
> @@ -52,7 +52,10 @@ void panfrost_perfcnt_clean_cache_done(struct panfrost_device *pfdev)
>  
>  void panfrost_perfcnt_sample_done(struct panfrost_device *pfdev)
>  {
> -	gpu_write(pfdev, GPU_CMD, GPU_CMD_CLEAN_CACHES);
> +	if (pfdev->features.selected_coherency != COHERENCY_ACE)

I think ACE_LITE would allow us to skip the flush to, so

	if (pfdev->features.selected_coherency == COHERENCY_NONE)

> +		gpu_write(pfdev, GPU_CMD, GPU_CMD_CLEAN_CACHES);
> +	else
> +		complete(&pfdev->perfcnt->dump_comp);
>  }
>  
>  static int panfrost_perfcnt_dump_locked(struct panfrost_device *pfdev)
>