5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zack Rusin <zack.ru...@broadcom.com>

[ Upstream commit a60ccade88f926e871a57176e86a34bbf0db0098 ]

The conditional was supposed to prevent enabling of a crtc state
without a set primary plane. Accidently it also prevented disabling
crtc state with a set primary plane. Neither is correct.

Fix the conditional and just driver-warn when a crtc state has been
enabled without a primary plane which will help debug broken userspace.

Fixes IGT's kms_atomic_interruptible and kms_atomic_transition tests.

Signed-off-by: Zack Rusin <zack.ru...@broadcom.com>
Fixes: 06ec41909e31 ("drm/vmwgfx: Add and connect CRTC helper functions")
Cc: Broadcom internal kernel review list <bcm-kernel-feedback-l...@broadcom.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <sta...@vger.kernel.org> # v4.12+
Reviewed-by: Ian Forbes <ian.for...@broadcom.com>
Reviewed-by: Martin Krastev <martin.kras...@broadcom.com>
Link: 
https://patchwork.freedesktop.org/patch/msgid/20240412025511.78553-5-zack.ru...@broadcom.com
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c 
b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index 01d5a01af2594..e2a52b5de1733 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -537,6 +537,7 @@ int vmw_du_cursor_plane_atomic_check(struct drm_plane 
*plane,
 int vmw_du_crtc_atomic_check(struct drm_crtc *crtc,
                             struct drm_atomic_state *state)
 {
+       struct vmw_private *vmw = vmw_priv(crtc->dev);
        struct drm_crtc_state *new_state = drm_atomic_get_new_crtc_state(state,
                                                                         crtc);
        struct vmw_display_unit *du = vmw_crtc_to_du(new_state->crtc);
@@ -544,9 +545,13 @@ int vmw_du_crtc_atomic_check(struct drm_crtc *crtc,
        bool has_primary = new_state->plane_mask &
                           drm_plane_mask(crtc->primary);
 
-       /* We always want to have an active plane with an active CRTC */
-       if (has_primary != new_state->enable)
-               return -EINVAL;
+       /*
+        * This is fine in general, but broken userspace might expect
+        * some actual rendering so give a clue as why it's blank.
+        */
+       if (new_state->enable && !has_primary)
+               drm_dbg_driver(&vmw->drm,
+                              "CRTC without a primary plane will be blank.\n");
 
 
        if (new_state->connector_mask != connector_mask &&
-- 
2.43.0



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