Re: [PATCH 15/23] drm: Stop updating plane->crtc/fb/old_fb on atomic drivers

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Mar 22, 2018 at 05:23:05PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Stop playing around with plane->crtc/fb/old_fb with atomic
> drivers. Make life a lot simpler when we don't have to do the
> magic old_fb vs. fb dance around plane updates. That way we
> can't risk plane->fb getting out of sync with plane->state->fb
> and we're less likely to leak any refcounts as well.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_atomic.c        | 55 ++++---------------------------------
>  drivers/gpu/drm/drm_atomic_helper.c | 15 +---------
>  drivers/gpu/drm/drm_crtc.c          |  8 ++++--
>  drivers/gpu/drm/drm_fb_helper.c     |  7 -----
>  drivers/gpu/drm/drm_framebuffer.c   |  5 ----
>  drivers/gpu/drm/drm_plane.c         | 14 ++++++----
>  drivers/gpu/drm/drm_plane_helper.c  |  4 ++-
>  include/drm/drm_atomic.h            |  3 --
>  8 files changed, 24 insertions(+), 87 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 7d25c42f22db..b16cc37e2adf 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -692,6 +692,11 @@ drm_atomic_get_plane_state(struct drm_atomic_state *state,
>  
>  	WARN_ON(!state->acquire_ctx);
>  
> +	/* the legacy pointers should never be set */
> +	WARN_ON(plane->fb);
> +	WARN_ON(plane->old_fb);
> +	WARN_ON(plane->crtc);

I did already review all the users for plane->crtc and found:

armada + shmob: not atomic, should be fine

But there's also exynos, msm/mdp5, sti and vc4 doing various silly things
with setting plane->crtc. I think before you can add this WARN_ON we need
to clean up that cruft (it looks like 100% cargo culting, so should be
quit).

Going to think about the other patches tomorrow.
-Daniel

> +
>  	plane_state = drm_atomic_get_existing_plane_state(state, plane);
>  	if (plane_state)
>  		return plane_state;
> @@ -2021,45 +2026,6 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
>  	return ret;
>  }
>  
> -/**
> - * drm_atomic_clean_old_fb -- Unset old_fb pointers and set plane->fb pointers.
> - *
> - * @dev: drm device to check.
> - * @plane_mask: plane mask for planes that were updated.
> - * @ret: return value, can be -EDEADLK for a retry.
> - *
> - * Before doing an update &drm_plane.old_fb is set to &drm_plane.fb, but before
> - * dropping the locks old_fb needs to be set to NULL and plane->fb updated. This
> - * is a common operation for each atomic update, so this call is split off as a
> - * helper.
> - */
> -void drm_atomic_clean_old_fb(struct drm_device *dev,
> -			     unsigned plane_mask,
> -			     int ret)
> -{
> -	struct drm_plane *plane;
> -
> -	/* if succeeded, fixup legacy plane crtc/fb ptrs before dropping
> -	 * locks (ie. while it is still safe to deref plane->state).  We
> -	 * need to do this here because the driver entry points cannot
> -	 * distinguish between legacy and atomic ioctls.
> -	 */
> -	drm_for_each_plane_mask(plane, dev, plane_mask) {
> -		if (ret == 0) {
> -			struct drm_framebuffer *new_fb = plane->state->fb;
> -			if (new_fb)
> -				drm_framebuffer_get(new_fb);
> -			plane->fb = new_fb;
> -			plane->crtc = plane->state->crtc;
> -
> -			if (plane->old_fb)
> -				drm_framebuffer_put(plane->old_fb);
> -		}
> -		plane->old_fb = NULL;
> -	}
> -}
> -EXPORT_SYMBOL(drm_atomic_clean_old_fb);
> -
>  /**
>   * DOC: explicit fencing properties
>   *
> @@ -2280,9 +2246,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  	unsigned int copied_objs, copied_props;
>  	struct drm_atomic_state *state;
>  	struct drm_modeset_acquire_ctx ctx;
> -	struct drm_plane *plane;
>  	struct drm_out_fence_state *fence_state;
> -	unsigned plane_mask;
>  	int ret = 0;
>  	unsigned int i, j, num_fences;
>  
> @@ -2322,7 +2286,6 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  	state->allow_modeset = !!(arg->flags & DRM_MODE_ATOMIC_ALLOW_MODESET);
>  
>  retry:
> -	plane_mask = 0;
>  	copied_objs = 0;
>  	copied_props = 0;
>  	fence_state = NULL;
> @@ -2393,12 +2356,6 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  			copied_props++;
>  		}
>  
> -		if (obj->type == DRM_MODE_OBJECT_PLANE && count_props &&
> -		    !(arg->flags & DRM_MODE_ATOMIC_TEST_ONLY)) {
> -			plane = obj_to_plane(obj);
> -			plane_mask |= (1 << drm_plane_index(plane));
> -			plane->old_fb = plane->fb;
> -		}
>  		drm_mode_object_put(obj);
>  	}
>  
> @@ -2419,8 +2376,6 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  	}
>  
>  out:
> -	drm_atomic_clean_old_fb(dev, plane_mask, ret);
> -
>  	complete_crtc_signaling(dev, state, fence_state, num_fences, !ret);
>  
>  	if (ret == -EDEADLK) {
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 0e806f070d00..d42d88b97396 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2892,7 +2892,6 @@ static int __drm_atomic_helper_disable_all(struct drm_device *dev,
>  	struct drm_plane *plane;
>  	struct drm_crtc_state *crtc_state;
>  	struct drm_crtc *crtc;
> -	unsigned int plane_mask = 0;
>  	int ret, i;
>  
>  	state = drm_atomic_state_alloc(dev);
> @@ -2935,17 +2934,10 @@ static int __drm_atomic_helper_disable_all(struct drm_device *dev,
>  			goto free;
>  
>  		drm_atomic_set_fb_for_plane(plane_state, NULL);
> -
> -		if (clean_old_fbs) {
> -			plane->old_fb = plane->fb;
> -			plane_mask |= BIT(drm_plane_index(plane));
> -		}
>  	}
>  
>  	ret = drm_atomic_commit(state);
>  free:
> -	drm_atomic_clean_old_fb(dev, plane_mask, ret);
> -
>  	drm_atomic_state_put(state);
>  	return ret;
>  }
> @@ -3106,13 +3098,8 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
>  
>  	state->acquire_ctx = ctx;
>  
> -	for_each_new_plane_in_state(state, plane, new_plane_state, i) {
> -		WARN_ON(plane->crtc != new_plane_state->crtc);
> -		WARN_ON(plane->fb != new_plane_state->fb);
> -		WARN_ON(plane->old_fb);
> -
> +	for_each_new_plane_in_state(state, plane, new_plane_state, i)
>  		state->planes[i].old_state = plane->state;
> -	}
>  
>  	for_each_new_crtc_in_state(state, crtc, new_crtc_state, i)
>  		state->crtcs[i].old_state = crtc->state;
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index a231dd5dce16..4e3c1a8d118a 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -474,8 +474,12 @@ static int __drm_mode_set_config_internal(struct drm_mode_set *set,
>  
>  	ret = crtc->funcs->set_config(set, ctx);
>  	if (ret == 0) {
> -		crtc->primary->crtc = fb ? crtc : NULL;
> -		crtc->primary->fb = fb;
> +		struct drm_plane *plane = crtc->primary;
> +
> +		if (!plane->state) {
> +			plane->crtc = fb ? crtc : NULL;
> +			plane->fb = fb;
> +		}
>  	}
>  
>  	drm_for_each_crtc(tmp, crtc->dev) {
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 0646b108030b..5639e804a0cd 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -368,7 +368,6 @@ static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper, bool activ
>  	struct drm_plane *plane;
>  	struct drm_atomic_state *state;
>  	int i, ret;
> -	unsigned int plane_mask;
>  	struct drm_modeset_acquire_ctx ctx;
>  
>  	drm_modeset_acquire_init(&ctx, 0);
> @@ -381,7 +380,6 @@ static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper, bool activ
>  
>  	state->acquire_ctx = &ctx;
>  retry:
> -	plane_mask = 0;
>  	drm_for_each_plane(plane, dev) {
>  		plane_state = drm_atomic_get_plane_state(state, plane);
>  		if (IS_ERR(plane_state)) {
> @@ -391,9 +389,6 @@ static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper, bool activ
>  
>  		plane_state->rotation = DRM_MODE_ROTATE_0;
>  
> -		plane->old_fb = plane->fb;
> -		plane_mask |= 1 << drm_plane_index(plane);
> -
>  		/* disable non-primary: */
>  		if (plane->type == DRM_PLANE_TYPE_PRIMARY)
>  			continue;
> @@ -430,8 +425,6 @@ static int restore_fbdev_mode_atomic(struct drm_fb_helper *fb_helper, bool activ
>  	ret = drm_atomic_commit(state);
>  
>  out_state:
> -	drm_atomic_clean_old_fb(dev, plane_mask, ret);
> -
>  	if (ret == -EDEADLK)
>  		goto backoff;
>  
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index ad67203de715..421a77c2a4ac 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -835,8 +835,6 @@ static int atomic_remove_fb(struct drm_framebuffer *fb)
>  			goto unlock;
>  
>  		plane_mask |= BIT(drm_plane_index(plane));
> -
> -		plane->old_fb = plane->fb;
>  	}
>  
>  	/* This list is only filled when disable_crtcs is set. */
> @@ -851,9 +849,6 @@ static int atomic_remove_fb(struct drm_framebuffer *fb)
>  		ret = drm_atomic_commit(state);
>  
>  unlock:
> -	if (plane_mask)
> -		drm_atomic_clean_old_fb(dev, plane_mask, ret);
> -
>  	if (ret == -EDEADLK) {
>  		drm_atomic_state_clear(state);
>  		drm_modeset_backoff(&ctx);
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 035054455301..143041666096 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -650,9 +650,11 @@ static int __setplane_internal(struct drm_plane *plane,
>  					 crtc_x, crtc_y, crtc_w, crtc_h,
>  					 src_x, src_y, src_w, src_h, ctx);
>  	if (!ret) {
> -		plane->crtc = crtc;
> -		plane->fb = fb;
> -		drm_framebuffer_get(plane->fb);
> +		if (!plane->state) {
> +			plane->crtc = crtc;
> +			plane->fb = fb;
> +			drm_framebuffer_get(plane->fb);
> +		}
>  	} else {
>  		plane->old_fb = NULL;
>  	}
> @@ -1092,8 +1094,10 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
>  		/* Keep the old fb, don't unref it. */
>  		plane->old_fb = NULL;
>  	} else {
> -		plane->fb = fb;
> -		drm_framebuffer_get(fb);
> +		if (!plane->state) {
> +			plane->fb = fb;
> +			drm_framebuffer_get(fb);
> +		}
>  	}
>  
>  out:
> diff --git a/drivers/gpu/drm/drm_plane_helper.c b/drivers/gpu/drm/drm_plane_helper.c
> index f88f68161519..2010794943bc 100644
> --- a/drivers/gpu/drm/drm_plane_helper.c
> +++ b/drivers/gpu/drm/drm_plane_helper.c
> @@ -502,6 +502,7 @@ EXPORT_SYMBOL(drm_plane_helper_update);
>  int drm_plane_helper_disable(struct drm_plane *plane)
>  {
>  	struct drm_plane_state *plane_state;
> +	struct drm_framebuffer *old_fb;
>  
>  	/* crtc helpers love to call disable functions for already disabled hw
>  	 * functions. So cope with that. */
> @@ -521,8 +522,9 @@ int drm_plane_helper_disable(struct drm_plane *plane)
>  	plane_state->plane = plane;
>  
>  	plane_state->crtc = NULL;
> +	old_fb = plane_state->fb;
>  	drm_atomic_set_fb_for_plane(plane_state, NULL);
>  
> -	return drm_plane_helper_commit(plane, plane_state, plane->fb);
> +	return drm_plane_helper_commit(plane, plane_state, old_fb);
>  }
>  EXPORT_SYMBOL(drm_plane_helper_disable);
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index a57a8aa90ffb..ca461b6cf71f 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -601,9 +601,6 @@ int __must_check
>  drm_atomic_add_affected_planes(struct drm_atomic_state *state,
>  			       struct drm_crtc *crtc);
>  
> -void
> -drm_atomic_clean_old_fb(struct drm_device *dev, unsigned plane_mask, int ret);
> -
>  int __must_check drm_atomic_check_only(struct drm_atomic_state *state);
>  int __must_check drm_atomic_commit(struct drm_atomic_state *state);
>  int __must_check drm_atomic_nonblocking_commit(struct drm_atomic_state *state);
> -- 
> 2.16.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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