[PATCH v4] drm/i915: Avoid GPU Hang when comming out of s3 or s4

Peter Antoine
2015-05-11T11:05:35Z

This patch fixed a timing issue that causes a GPU hang when a the system
comes out of power saving.

During pm_resume, We are submitting batchbuffers before enabling
Interrupts this is causing us to miss the context switch interrupt,
and in consequence intel_execlists_handle_ctx_events is not triggered.

This patch is based on a patch from Deepak S <deepak.s@intel.com>
from another platform.

The patch fixes an issue introduced by:
commit e7778be1eab918274f79603d7c17b3ec8be77386
drm/i915: Fix startup failure in LRC mode after recent init changes

The above patch added a call to init_context() to fix an issue introduced
by a previous patch. But, it then opened up a small timing window for the
batches being added by the init_context (basically setting up the context)
to complete before the interrupts have been turned on, thus hanging the
GPU.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89600
Signed-off-by: Peter Antoine <peter.antoine@intel.com>
---
drivers/gpu/drm/i915/i915_drv.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 6bb6c47..748ab13 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -734,6 +734,13 @@ static int i915_drm_resume(struct drm_device *dev)
intel_init_pch_refclk(dev);
drm_mode_config_reset(dev);

+ /*
+ * Interrupts have to be enabled before any batches are run. If not the
+ * GPU will hang. The init_hw will initiate batches to update/restore
+ * the context.
+ */
+ intel_runtime_pm_enable_interrupts(dev_priv);
+
mutex_lock(&dev->struct_mutex);
if (i915_gem_init_hw(dev)) {
DRM_ERROR("failed to re-initialize GPU, declaring wedged!\n");
@@ -741,9 +748,7 @@ static int i915_drm_resume(struct drm_device *dev)
}
mutex_unlock(&dev->struct_mutex);

- /* We need working interrupts for modeset enabling ... */
- intel_runtime_pm_enable_interrupts(dev_priv);
-
+ /* This must follow the pm enable interrupts */
intel_modeset_init_hw(dev);

spin_lock_irq(&dev_priv->irq_lock);
--
1.9.1