[PATCH 3/7] drm/vmwgfx: Stop using plane->fb in vmw_kms_helper_dirty()

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Instead of plane->fb (which we're going to deprecate for atomic drivers)
we need to look at plane->state->fb. The maze of code leading to
vmw_kms_helper_dirty() wasn't particularly clear, but my analysis
concluded that the calls originating from vmw_*_primary_plane_atomic_update()
all pass in the crtc which means we'll never end up in this branch
of the function. All other callers use drm_modeset_lock_all() somewhere
higher up, which means accessing plane->state is safe. We'll toss in
a lockdep assert to catch wrongdoers.

Cc: Thomas Hellstrom <thellstrom at vmware.com>
Cc: Sinclair Yeh <syeh at vmware.com>
Cc: VMware Graphics <linux-graphics-maintainer at vmware.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index a2a796b4cc23..5a824125c231 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -2326,9 +2326,18 @@ int vmw_kms_helper_dirty(struct vmw_private *dev_priv,
 	} else {
 		list_for_each_entry(crtc, &dev_priv->dev->mode_config.crtc_list,
 				    head) {
-			if (crtc->primary->fb != &framebuffer->base)
-				continue;
-			units[num_units++] = vmw_crtc_to_du(crtc);
+			struct drm_plane *plane = crtc->primary;
+
+			/*
+			 * vmw_*_primary_plane_atomic_update() pass in the crtc,
+			 * and so don't end up here. All other callers use
+			 * drm_modeset_lock_all(), hence we can access the
+			 * plane state safely.
+			 */
+			lockdep_assert_held(&plane->mutex);
+
+			if (plane->state->fb != &framebuffer->base)
+				units[num_units++] = vmw_crtc_to_du(crtc);
 		}
 	}
 
-- 
2.16.1