drm/i915: Clear scanline waits after disabling the pipe.
If we disable the pipe and the GPU is currently waiting on a scanline
WAIT_FOR_EVENT, the GPU will hang. Fortunately, there is a magic bit
which we can write on i915+ to break this wait after disabling the
pipe.
References:
Bug 29252 - [Arrandale] Hung WAIT_FOR_EVENT when running rss-glx-skyrocket
https://bugs.freedesktop.org/show_bug.cgi?id=29252
Bug 28964 - [i965gm] GPU infinite MI_WAIT_FOR_EVENT while watching video in Totem
https://bugs.freedesktop.org/show_bug.cgi?id=28964
and many others.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 0b400d1..d5cb7ba 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2344,6 +2344,26 @@
}
}
+/*
+ * When we disable a pipe, we need to clear any pending scanline wait events
+ * to avoid hanging the ring, which we assume we are waiting on.
+ */
+static void intel_clear_scanline_wait(struct drm_device *dev)
+{
+ struct drm_i915_private *dev_priv = dev->dev_private;
+ u32 tmp;
+
+ if (IS_GEN2(dev))
+ /* Can't break the hang on i8xx */
+ return;
+
+ tmp = I915_READ(PRB0_CTL);
+ if (tmp & RING_WAIT) {
+ I915_WRITE(PRB0_CTL, tmp);
+ POSTING_READ(PRB0_CTL);
+ }
+}
+
/**
* Sets the power management mode of the pipe and plane.
*/
@@ -2366,7 +2386,8 @@
* with multiple pipes prior to enabling to new pipe.
*
* When switching off the display, make sure the cursor is
- * properly hidden prior to disabling the pipe.
+ * properly hidden and there are no pending waits prior to
+ * disabling the pipe.
*/
if (mode == DRM_MODE_DPMS_ON)
intel_update_watermarks(dev);
@@ -2377,8 +2398,14 @@
if (mode == DRM_MODE_DPMS_ON)
intel_crtc_update_cursor(crtc);
- else
+ else {
+ /* XXX Note that this is not a complete solution, but a hack
+ * to avoid the most frequently hit hang.
+ */
+ intel_clear_scanline_wait(dev);
+
intel_update_watermarks(dev);
+ }
if (!dev->primary->master)
return;