Re: [PATCH v2 1/2] drm/atomic: move waiting for hw_done to a helper

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jun 14, 2017 at 11:08:41AM +0200, Maarten Lankhorst wrote:
> Moving the wait to a helper allows callers outside of the core to
> wait for pending updates to complete.
> 
> This can be used to prevent races against nonblocking modesets.
> Only the hw_done call in swap_state is moved to a helper, doing
> it for the other callers requires too many changes and I think this
> is the only useful one to export.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 51 +++++++++++++++++++++++++++----------
>  include/drm/drm_atomic_helper.h     |  1 +
>  2 files changed, 38 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 86d3093c6c9b..1b068ce1aea9 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2067,6 +2067,41 @@ void drm_atomic_helper_cleanup_planes(struct drm_device *dev,
>  EXPORT_SYMBOL(drm_atomic_helper_cleanup_planes);
>  
>  /**
> + * drm_atomic_helper_wait_for_hw_done - wait for all previous hw updates to complete.
> + * @crtc: crtc to wait on.
> + *
> + * This function waits for all previous hardware updates queued on @crtc
> + * to complete.
> + *
> + * Returns:
> + * 0 on success, negative error code on failure.
> + */
> +int drm_atomic_helper_wait_for_hw_done(struct drm_crtc *crtc)
> +{
> +	struct drm_crtc_commit *commit;
> +	long ret;
> +
> +	spin_lock(&crtc->commit_lock);
> +	commit = list_first_entry_or_null(&crtc->commit_list,
> +			struct drm_crtc_commit, commit_entry);
> +	if (commit)
> +		drm_crtc_commit_get(commit);
> +	spin_unlock(&crtc->commit_lock);
> +
> +	if (!commit)
> +		return 0;
> +
> +	ret = wait_for_completion_timeout(&commit->hw_done, 10 * HZ);
> +	drm_crtc_commit_put(commit);
> +
> +	if (ret == 0)
> +		return -EBUSY;

-ETIMEDOUT ?

> +
> +	return ret > 0 ? 0 : ret;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_wait_for_hw_done);
> +
> +/**
>   * drm_atomic_helper_swap_state - store atomic state into current sw state
>   * @state: atomic state
>   * @stall: stall for proceeding commits
> @@ -2107,28 +2142,16 @@ void drm_atomic_helper_swap_state(struct drm_atomic_state *state,
>  	struct drm_crtc_state *old_crtc_state, *new_crtc_state;
>  	struct drm_plane *plane;
>  	struct drm_plane_state *old_plane_state, *new_plane_state;
> -	struct drm_crtc_commit *commit;
>  	void *obj, *obj_state;
>  	const struct drm_private_state_funcs *funcs;
>  
>  	if (stall) {
>  		for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
> -			spin_lock(&crtc->commit_lock);
> -			commit = list_first_entry_or_null(&crtc->commit_list,
> -					struct drm_crtc_commit, commit_entry);
> -			if (commit)
> -				drm_crtc_commit_get(commit);
> -			spin_unlock(&crtc->commit_lock);
> +			ret = drm_atomic_helper_wait_for_hw_done(crtc);
>  
> -			if (!commit)
> -				continue;
> -
> -			ret = wait_for_completion_timeout(&commit->hw_done,
> -							  10*HZ);
> -			if (ret == 0)
> +			if (ret < 0)
>  				DRM_ERROR("[CRTC:%d:%s] hw_done timed out\n",
>  					  crtc->base.id, crtc->name);
> -			drm_crtc_commit_put(commit);
>  		}
>  	}
>  
> diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
> index f0a8678ae98e..175a1a3fed36 100644
> --- a/include/drm/drm_atomic_helper.h
> +++ b/include/drm/drm_atomic_helper.h
> @@ -77,6 +77,7 @@ void
>  drm_atomic_helper_disable_planes_on_crtc(struct drm_crtc_state *old_crtc_state,
>  					 bool atomic);
>  
> +int drm_atomic_helper_wait_for_hw_done(struct drm_crtc *crtc);
>  void drm_atomic_helper_swap_state(struct drm_atomic_state *state,
>  				  bool stall);
>  
> -- 
> 2.11.0
> 
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-- 
Ville Syrjälä
Intel OTC
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