[PATCH] drm/i915: Disable high-precision vblank timestamping for UMS

[Chris Wilson]

We only have sufficient information for accurate (sub-frame) timestamping
when the modesetting is under our control.

Reported-by: Chris Clayton <chris2553 at googlemail.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 59eb19b..66796bb 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -752,6 +752,9 @@ static int __init i915_init(void)
 		driver.driver_features &= ~DRIVER_MODESET;
 #endif
 
+	if (!(driver.driver_features & DRIVER_MODESET))
+		driver.get_vblank_timestamp = NULL;
+
 	return drm_init(&driver);
 }
 
-- 
1.7.2.3