On 04/05/2018 09:50 PM, Ville Syrjala wrote:
From: Ville Syrjälä <ville.syrj...@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 <thellst...@vmware.com>
Cc: Sinclair Yeh <s...@vmware.com>
Cc: VMware Graphics <linux-graphics-maintai...@vmware.com>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrj...@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 
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);
I think we can remove the comment (it's a helper, so current users may not be future users),
but the lockdep assert should be OK.
+                       if (plane->state->fb != &framebuffer->base)
+                               units[num_units++] = vmw_crtc_to_du(crtc);

This doesn't seem to do what the original code did...



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