On Wed, 3 Dec 2025 12:05:27 +0100
Boris Brezillon <[email protected]> wrote:
> An AS can be disabled in the middle of a VM operation (VM being
> evicted from an AS slot, for instance). In that case, we need the
> locked section to be unlocked before releasing the slot.
>
> v2:
> - Add an lockdep_assert_held() in panthor_mmu_as_disable()
> - Collect R-bs
>
> Fixes: 6e2d3b3e8589 ("drm/panthor: Add support for atomic page table updates")
> Signed-off-by: Boris Brezillon <[email protected]>
> Reviewed-by: Liviu Dudau <[email protected]>
> Reviewed-by: Chia-I Wu <[email protected]>
> ---
> drivers/gpu/drm/panthor/panthor_mmu.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c
> b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 3644af1a8e56..493e6428d478 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -588,14 +588,27 @@ static int panthor_mmu_as_enable(struct panthor_device
> *ptdev, u32 as_nr,
> static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr,
> bool recycle_slot)
> {
> + struct panthor_vm *vm = ptdev->mmu->as.slots[as_nr].vm;
> int ret;
>
> + lockdep_assert_held(&ptdev->mmu->as.slots_lock);
> +
> /* Flush+invalidate RW caches, invalidate RO ones. */
> ret = panthor_gpu_flush_caches(ptdev, CACHE_CLEAN | CACHE_INV,
> CACHE_CLEAN | CACHE_INV, CACHE_INV);
> if (ret)
> return ret;
>
> + if (vm && vm->locked_region.size) {
> + /* Unlock the region if there a lock pending. */
> + ret = as_send_cmd_and_wait(ptdev, vm->as.id, AS_COMMAND_UNLOCK);
> + if (ret)
> + return ret;
> +
> + vm->locked_region.start = 0;
> + vm->locked_region.size = 0;
Actually, resetting the locked_region range triggers the WARN_ON()s in
the vm_[un]map_pages() path, so I'll get rid of that in v3.
> + }
> +
> /* If the slot is going to be used immediately, don't bother changing
> * the config.
> */
