Re: [PATCH 1/3] drm/panthor: Don't invalidate OTHER caches

[Liviu Dudau <liviu.dudau@arm.com>]

On Thu, Sep 24, 2026 at 02:30:43PM +0200, Boris Brezillon wrote:
> Don't invalidate the OTHER caches (AKA L1 read-only caches) since
> this seems to trip out the flush-elimination logic on v13, and it's not
> needed in practice (can't leak other context data because of TLB
> invalidation or corrupt physical pages returned to the system because
> it's a RO cache).
> 
> It's also worth noting that the downstream driver has been avoid
> OTHER caches invalidation from the start, and that we were doing
> the same until atomic page table update was introduced.
> 
> Fixes: 6e2d3b3e8589 ("drm/panthor: Add support for atomic page table updates")
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 9f63a048df61..7e98084b9a1e 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -634,7 +634,7 @@ static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr,
>  
>  	/* Flush+invalidate RW caches, invalidate RO ones. */
>  	ret = panthor_gpu_flush_caches(ptdev, CACHE_CLEAN | CACHE_INV,
> -				       CACHE_CLEAN | CACHE_INV, CACHE_INV);
> +				       CACHE_CLEAN | CACHE_INV, 0);
>  	if (ret)
>  		return ret;
>  
> @@ -1841,8 +1841,7 @@ static void panthor_vm_unlock_region(struct panthor_vm *vm)
>  		 * range is narrow enough and the HW supports it.
>  		 */
>  		ret = panthor_gpu_flush_caches(ptdev, CACHE_CLEAN | CACHE_INV,
> -					       CACHE_CLEAN | CACHE_INV,
> -					       CACHE_INV);
> +					       CACHE_CLEAN | CACHE_INV, 0);
>  
>  		/* Unlock the region if the flush is effective. */
>  		if (!ret)
> 
> -- 
> 2.55.0
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
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