Re: [Intel-gfx] [PATCH v1 3/3] drm/i915/gt: Timeout when waiting for idle in suspending

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Wed, Aug 02, 2023 at 04:35:01PM -0700, Alan Previn wrote:
> When suspending, add a timeout when calling
> intel_gt_pm_wait_for_idle else if we have a lost
> G2H event that holds a wakeref (which would be
> indicating of a bug elsewhere in the driver), we
> get to complete the suspend-resume cycle, albeit
> without all the lower power hw counters hitting
> its targets, instead of hanging in the kernel.
> 
> Signed-off-by: Alan Previn <alan.previn.teres.alexis@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c |  2 +-
>  drivers/gpu/drm/i915/gt/intel_gt_pm.c     |  7 ++++++-
>  drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  7 ++++++-
>  drivers/gpu/drm/i915/intel_wakeref.c      | 14 ++++++++++----
>  drivers/gpu/drm/i915/intel_wakeref.h      |  5 +++--
>  5 files changed, 26 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index ee15486fed0d..090438eb8682 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -688,7 +688,7 @@ void intel_engines_release(struct intel_gt *gt)
>  		if (!engine->release)
>  			continue;
>  
> -		intel_wakeref_wait_for_idle(&engine->wakeref);
> +		intel_wakeref_wait_for_idle(&engine->wakeref, 0);
>  		GEM_BUG_ON(intel_engine_pm_is_awake(engine));
>  
>  		engine->release(engine);
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> index 3162d859ed68..dfe77eb3efd1 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> @@ -289,6 +289,8 @@ int intel_gt_resume(struct intel_gt *gt)
>  
>  static void wait_for_suspend(struct intel_gt *gt)
>  {
> +	int timeout_ms = CONFIG_DRM_I915_MAX_REQUEST_BUSYWAIT ? : 10000;
> +
>  	if (!intel_gt_pm_is_awake(gt)) {
>  		intel_uc_suspend_prepare(&gt->uc);
>  		return;
> @@ -305,7 +307,10 @@ static void wait_for_suspend(struct intel_gt *gt)
>  		intel_uc_suspend_prepare(&gt->uc);
>  	}
>  
> -	intel_gt_pm_wait_for_idle(gt);
> +	/* we are suspending, so we shouldn't be waiting forever */
> +	if (intel_gt_pm_wait_timeout_for_idle(gt, timeout_ms) == -ETIME)
> +		drm_warn(&gt->i915->drm, "Bailing from %s after %d milisec timeout\n",
> +			 __func__, timeout_ms);
>  }
>  
>  void intel_gt_suspend_prepare(struct intel_gt *gt)
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> index 6c9a46452364..5358acc2b5b1 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
> @@ -68,7 +68,12 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
>  
>  static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
>  {
> -	return intel_wakeref_wait_for_idle(&gt->wakeref);
> +	return intel_wakeref_wait_for_idle(&gt->wakeref, 0);
> +}
> +
> +static inline int intel_gt_pm_wait_timeout_for_idle(struct intel_gt *gt, int timeout_ms)
> +{
> +	return intel_wakeref_wait_for_idle(&gt->wakeref, timeout_ms);
>  }
>  
>  void intel_gt_pm_init_early(struct intel_gt *gt);
> diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
> index 718f2f1b6174..7e01d4cc300c 100644
> --- a/drivers/gpu/drm/i915/intel_wakeref.c
> +++ b/drivers/gpu/drm/i915/intel_wakeref.c
> @@ -111,14 +111,20 @@ void __intel_wakeref_init(struct intel_wakeref *wf,
>  			 "wakeref.work", &key->work, 0);
>  }
>  
> -int intel_wakeref_wait_for_idle(struct intel_wakeref *wf)
> +int intel_wakeref_wait_for_idle(struct intel_wakeref *wf, int timeout_ms)
>  {
> -	int err;
> +	int err = 0;
>  
>  	might_sleep();
>  
> -	err = wait_var_event_killable(&wf->wakeref,
> -				      !intel_wakeref_is_active(wf));
> +	if (!timeout_ms)
> +		err = wait_var_event_killable(&wf->wakeref,
> +					      !intel_wakeref_is_active(wf));
> +	else if (wait_var_event_timeout(&wf->wakeref,
> +					!intel_wakeref_is_active(wf),
> +					msecs_to_jiffies(timeout_ms)) < 1)
> +		err = -ETIME;

it looks to me that -ETIMEDOUT would be a better error.

> +
>  	if (err)
>  		return err;
>  
> diff --git a/drivers/gpu/drm/i915/intel_wakeref.h b/drivers/gpu/drm/i915/intel_wakeref.h
> index ec881b097368..6fbb7a2fb6ea 100644
> --- a/drivers/gpu/drm/i915/intel_wakeref.h
> +++ b/drivers/gpu/drm/i915/intel_wakeref.h
> @@ -251,15 +251,16 @@ __intel_wakeref_defer_park(struct intel_wakeref *wf)
>  /**
>   * intel_wakeref_wait_for_idle: Wait until the wakeref is idle
>   * @wf: the wakeref
> + * @timeout_ms: timeout to wait in milisecs, zero means forever
>   *
>   * Wait for the earlier asynchronous release of the wakeref. Note
>   * this will wait for any third party as well, so make sure you only wait
>   * when you have control over the wakeref and trust no one else is acquiring
>   * it.
>   *
> - * Return: 0 on success, error code if killed.
> + * Return: 0 on success, error code if killed, -ETIME if timed-out.
>   */
> -int intel_wakeref_wait_for_idle(struct intel_wakeref *wf);
> +int intel_wakeref_wait_for_idle(struct intel_wakeref *wf, int timeout_ms);
>  
>  struct intel_wakeref_auto {
>  	struct drm_i915_private *i915;
> -- 
> 2.39.0
>