Re: [Intel-gfx] [PATCH v5] drm/i915: Avoid GPU Hang when comming out of s3 or s4

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 11 May 2015, Peter Antoine <peter.antoine@intel.com> wrote:
> 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
> Cc: stable@vger.kernel.org
> Signed-off-by: Peter Antoine <peter.antoine@intel.com>

I pushed some version of this patch to drm-intel-fixes yesterday, with
some comment modifications. Thanks for the patch and review.

For future reference, please add some changelog to your patches so it's
easier to know what's changed between versions.

BR,
Jani.

> ---
>  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
>
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-- 
Jani Nikula, Intel Open Source Technology Center