Re: [PATCH v3] drm/i915: Avoid GPU Hang when comming out of s3 or s4

Daniel Vetter
2015-05-11T11:53:39Z

On Mon, May 11, 2015 at 08:50:45AM +0100, Peter Antoine wrote:
> This patch fixes a timing issue that causes a GPU hang when 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.
>
> BUG: https://bugs.freedesktop.org/show_bug.cgi?id=89600
> Signed-off-by: Peter Antoine <peter.antoine@intel.com>

btw can you please follow up with a patch to encode these depencies? A

WARN_ON(!irqs_enabled);

in execlists_context_unqueue after the spinlock assert would be good I
think.
-Daniel

> ---
> drivers/gpu/drm/i915/i915_drv.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 6bb6c47..90b1309 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -734,6 +734,12 @@ static int i915_drm_resume(struct drm_device *dev)
> intel_init_pch_refclk(dev);
> drm_mode_config_reset(dev);
>
> + /* Interrupts have to enabled so that any batches that are completed
> + * when the context is restarted are caught so that the ring buffer
> + * does not handle.
> + */
> + 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 +747,7 @@ 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
>

--
Daniel Vetter
Software Engineer, Intel Corporation