[PATCH] Revert "drm/imx: Annotate dma-fence critical section in commit path"

[Daniel Vetter]

On Wed, Nov 03, 2021 at 09:11:12PM -0300, Fabio Estevam wrote:
> This reverts commit f4b34faa08428d813fc3629f882c503487f94a12.
> 
> Since commit f4b34faa0842 ("drm/imx: Annotate dma-fence critical section in
> commit path") the following possible circular dependency is detected:
> 
> [    5.001811] ======================================================
> [    5.001817] WARNING: possible circular locking dependency detected
> [    5.001824] 5.14.9-01225-g45da36cc6fcc-dirty #1 Tainted: G        W
> [    5.001833] ------------------------------------------------------
> [    5.001838] kworker/u8:0/7 is trying to acquire lock:
> [    5.001848] c1752080 (regulator_list_mutex){+.+.}-{3:3}, at: regulator_lock_dependent+0x40/0x294
> [    5.001903]
> [    5.001903] but task is already holding lock:
> [    5.001909] c176df78 (dma_fence_map){++++}-{0:0}, at: imx_drm_atomic_commit_tail+0x10/0x160
> [    5.001957]
> [    5.001957] which lock already depends on the new lock.
> ...
> 
> Revert it for now.
> 
> Tested on a imx6q-sabresd.
> 
> Fixes: f4b34faa0842 ("drm/imx: Annotate dma-fence critical section in commit path")
> Signed-off-by: Fabio Estevam <festevam at gmail.com>

Yeah I have these on my todo list since a while, I need to properly
document the reasons why this doesn't work.

Queued up for the merge window, thanks for your patch.
-Daniel

> ---
>  drivers/gpu/drm/imx/imx-drm-core.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imx/imx-drm-core.c b/drivers/gpu/drm/imx/imx-drm-core.c
> index 9558e9e1b431..cb685fe2039b 100644
> --- a/drivers/gpu/drm/imx/imx-drm-core.c
> +++ b/drivers/gpu/drm/imx/imx-drm-core.c
> @@ -81,7 +81,6 @@ static void imx_drm_atomic_commit_tail(struct drm_atomic_state *state)
>  	struct drm_plane_state *old_plane_state, *new_plane_state;
>  	bool plane_disabling = false;
>  	int i;
> -	bool fence_cookie = dma_fence_begin_signalling();
>  
>  	drm_atomic_helper_commit_modeset_disables(dev, state);
>  
> @@ -112,7 +111,6 @@ static void imx_drm_atomic_commit_tail(struct drm_atomic_state *state)
>  	}
>  
>  	drm_atomic_helper_commit_hw_done(state);
> -	dma_fence_end_signalling(fence_cookie);
>  }
>  
>  static const struct drm_mode_config_helper_funcs imx_drm_mode_config_helpers = {
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch