Re: [PATCH] drm/i915: Avoid GPU hang when coming out of s3 or s4

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

On Mon, 22 Jun 2015, Peter Antoine <peter.antoine@intel.com> 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.
>
> [backport of 4.1 commit 364aece01a2dd748fc36a1e8bf52ef639b0857bd]
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89600
> Cc: stable@vger.kernel.org # 4.0+
> Signed-off-by: Peter Antoine <peter.antoine@intel.com>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> [Jani: fixed typo in subject, massaged the comments a bit]
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Acked-by: Jani Nikula <jani.nikula@intel.com>

...although based on the patch context I'm not sure why this needs a
separate backport. Does it not cherry-pick cleanly to 4.0? The stable
team should take care of these automatically.

BR,
Jani.

> ---
>  drivers/gpu/drm/i915/i915_drv.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index ec4d932..169123a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -693,6 +693,16 @@ 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. i915_gem_init_hw() will initiate
> +		 * batches to update/restore the context.
> +		 *
> +		 * Modeset enabling in intel_modeset_init_hw() also needs
> +		 * working interrupts.
> +		 */
> +		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");
> @@ -700,9 +710,6 @@ 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);
> -
>  		intel_modeset_init_hw(dev);
>  
>  		spin_lock_irq(&dev_priv->irq_lock);
> -- 
> 1.9.1
>

-- 
Jani Nikula, Intel Open Source Technology Center
--
To unsubscribe from this list: send the line "unsubscribe stable" in