[PATCH] drm/drm_vblank: use drm_warn_once() to warn undefined mode timing

[Shawn Guo]

Commit 5caa0feafcc6 ("drm/vblank: Lock down vblank->hwmode more") added
WARN_ON_ONCE() for atomic drivers to warn the case that vsync is enabled
before a mode has been set on CRTC.  This happens sometimes during the
initial mode setting of a CRTC.  It also happens on Android running HWC2
backed with drm_hwcomposer, where HWC2::SetVsyncEnabled could be called
before the atomic mode setting on CRTC happens.

In this case, there is nothing really bad to happen as kernel function
returns as no-op.  So using WARN() version might be overkilled,
considering some user space crash reporting services may treat kernel
WARNINGS as crashes.  Let's drop WARN_ON_ONCE() and change drm_dbg_core()
to drm_warn_once() for warning undefined mode timing.

Signed-off-by: Shawn Guo <shawn.guo at linaro.org>
---
 drivers/gpu/drm/drm_vblank.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index b18e1efbbae1..5f7c4a923e8a 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -717,9 +717,9 @@ drm_crtc_vblank_helper_get_vblank_timestamp_internal(
 	 * Happens during initial modesetting of a crtc.
 	 */
 	if (mode->crtc_clock == 0) {
-		drm_dbg_core(dev, "crtc %u: Noop due to uninitialized mode.\n",
-			     pipe);
-		drm_WARN_ON_ONCE(dev, drm_drv_uses_atomic_modeset(dev));
+		drm_warn_once(dev, "crtc %u: Noop due to uninitialized mode.\n",
+			      pipe);
+
 		return false;
 	}
 
-- 
2.17.1