drm/i915: Avoid pageflipping freeze when we miss the flip prepare interrupt

When we miss the flip prepare interrupt, we never get into the
software state needed to restart userspace, resulting in a freeze of a
full-screen OpenGL application (such as a compositor).

Work around this by checking DSPxSURF/DSPxBASE to see if the page flip
has actually happened. If it has, do the work we would have done when
the flip prepare interrupt comes in.

Also, add debugfs information to tell us what's going on (based on the
patch from Chris Wilson attached to bugs.fdo bug #29798).

Signed-off-by: Simon Farnsworth <simon.farnsworth@onelan.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 50 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 92d5605a34d1..5e43d7076789 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -31,6 +31,7 @@
 #include <linux/slab.h>
 #include "drmP.h"
 #include "drm.h"
+#include "intel_drv.h"
 #include "i915_drm.h"
 #include "i915_drv.h"
 
@@ -121,6 +122,54 @@ static int i915_gem_object_list_info(struct seq_file *m, void *data)
         return 0;
 }
 
+static int i915_gem_pageflip_info(struct seq_file *m, void *data)
+{
+        struct drm_info_node *node = (struct drm_info_node *) m->private;
+        struct drm_device *dev = node->minor->dev;
+        unsigned long flags;
+        struct intel_crtc *crtc;
+
+        list_for_each_entry(crtc, &dev->mode_config.crtc_list, base.head) {
+                const char *pipe = crtc->pipe ? "B" : "A";
+                const char *plane = crtc->plane ? "B" : "A";
+                struct intel_unpin_work *work;
+
+                spin_lock_irqsave(&dev->event_lock, flags);
+                work = crtc->unpin_work;
+                if (work == NULL) {
+                        seq_printf(m, "No flip due on pipe %s (plane %s)\n",
+                                   pipe, plane);
+                } else {
+                        if (!work->pending) {
+                                seq_printf(m, "Flip queued on pipe %s (plane %s)\n",
+                                           pipe, plane);
+                        } else {
+                                seq_printf(m, "Flip pending (waiting for vsync) on pipe %s (plane %s)\n",
+                                           pipe, plane);
+                        }
+                        if (work->enable_stall_check)
+                                seq_printf(m, "Stall check enabled, ");
+                        else
+                                seq_printf(m, "Stall check waiting for page flip ioctl, ");
+                        seq_printf(m, "%d prepares\n", work->pending);
+
+                        if (work->old_fb_obj) {
+                                struct drm_i915_gem_object *obj_priv = to_intel_bo(work->old_fb_obj);
+                                if(obj_priv)
+                                        seq_printf(m, "Old framebuffer gtt_offset 0x%08x\n", obj_priv->gtt_offset );
+                        }
+                        if (work->pending_flip_obj) {
+                                struct drm_i915_gem_object *obj_priv = to_intel_bo(work->pending_flip_obj);
+                                if(obj_priv)
+                                        seq_printf(m, "New framebuffer gtt_offset 0x%08x\n", obj_priv->gtt_offset );
+                        }
+                }
+                spin_unlock_irqrestore(&dev->event_lock, flags);
+        }
+
+        return 0;
+}
+
 static int i915_gem_request_info(struct seq_file *m, void *data)
 {
         struct drm_info_node *node = (struct drm_info_node *) m->private;
@@ -777,6 +826,7 @@ static struct drm_info_list i915_debugfs_list[] = {
         {"i915_gem_active", i915_gem_object_list_info, 0, (void *) ACTIVE_LIST},
         {"i915_gem_flushing", i915_gem_object_list_info, 0, (void *) FLUSHING_LIST},
         {"i915_gem_inactive", i915_gem_object_list_info, 0, (void *) INACTIVE_LIST},
+        {"i915_gem_pageflip", i915_gem_pageflip_info, 0},
         {"i915_gem_request", i915_gem_request_info, 0},
         {"i915_gem_seqno", i915_gem_seqno_info, 0},
         {"i915_gem_fence_regs", i915_gem_fence_regs_info, 0},