[Bug 102675] [BDW] *ERROR* CPU pipe A|B|C FIFO underrun - Regression - Bisected

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=102675

--- Comment #2 from Marta Löfstedt <marta.lofstedt at intel.com> ---
Maarten Lankhorst suggested to test with the following:

"
diff --git a/drivers/gpu/drm/i915/intel_display.c
b/drivers/gpu/drm/i915/intel_display.c
index f77e73c72662..f096c55b35fa 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12514,23 +12514,14 @@ static int intel_atomic_commit(struct drm_device
*dev,
 {
        struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
        struct drm_i915_private *dev_priv = to_i915(dev);
-       int ret = 0;
-
-       ret = drm_atomic_helper_setup_commit(state, nonblock);
-       if (ret)
-               return ret;
+       struct drm_crtc_state *new_crtc_state;
+       struct drm_crtc *crtc;
+       int i, ret = 0;

        drm_atomic_state_get(state);
        i915_sw_fence_init(&intel_state->commit_ready,
                           intel_atomic_commit_ready);

-       ret = intel_atomic_prepare_commit(dev, state);
-       if (ret) {
-               DRM_DEBUG_ATOMIC("Preparing state failed with %i\n", ret);
-               i915_sw_fence_commit(&intel_state->commit_ready);
-               return ret;
-       }
-
        /*
         * The intel_legacy_cursor_update() fast path takes care
         * of avoiding the vblank waits for simple cursor
@@ -12548,10 +12539,23 @@ static int intel_atomic_commit(struct drm_device
*dev,
         * FIXME doing watermarks and fb cleanup from a vblank worker
         * (assuming we had any) would solve these problems.
         */
-       if (INTEL_GEN(dev_priv) < 9)
-               state->legacy_cursor_update = false;
+       if (INTEL_GEN(dev_priv) < 9 && state->legacy_cursor_update) {
+               for_each_new_crtc_in_state(state, crtc, new_crtc_state, i)
+                       if
(to_intel_crtc_state(new_crtc_state)->wm.need_postvbl_update)
+                               state->legacy_cursor_update = false;
+       }
+
+       ret = intel_atomic_prepare_commit(dev, state);
+       if (ret) {
+               DRM_DEBUG_ATOMIC("Preparing state failed with %i\n", ret);
+               i915_sw_fence_commit(&intel_state->commit_ready);
+               return ret;
+       }
+
+       ret = drm_atomic_helper_setup_commit(state, nonblock);
+       if (!ret)
+               ret = drm_atomic_helper_swap_state(state, true);

-       ret = drm_atomic_helper_swap_state(state, true);
        if (ret) {
                i915_sw_fence_commit(&intel_state->commit_ready);

@@ -12579,7 +12583,6 @@ static int intel_atomic_commit(struct drm_device *dev,
        else
                intel_atomic_commit_tail(state);

-
        return 0;
 }
"

With above I can't reproduce the issue.

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