Re: [PATCH 1/9] drm/i915: Flush logical context image out to memory upon suspend

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Before suspend, and especially before building the hibernation image, we
> need to context image to be coherent in memory. To do this we require
> that we perform a context switch to a disposable context (i.e. the
> dev_priv->kernel_context) - when that switch is complete, all other
> context images will be complete. This leaves the kernel_context image as
> incomplete, but fortunately that is disposable and we can do a quick
> fixup of the logical state after resuming.
>
> Testcase: igt/gem_exec_suspend # bsw
> References: https://bugs.freedesktop.org/show_bug.cgi?id=96526
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.c |  4 +---
>  drivers/gpu/drm/i915/i915_drv.h |  1 +
>  drivers/gpu/drm/i915/i915_gem.c | 46 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 48 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 15440123e38d..c5b7b8e0678a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1590,9 +1590,7 @@ static int i915_drm_resume(struct drm_device *dev)
>  
>  	intel_csr_ucode_resume(dev_priv);
>  
> -	mutex_lock(&dev->struct_mutex);
> -	i915_gem_restore_gtt_mappings(dev);
> -	mutex_unlock(&dev->struct_mutex);
> +	i915_gem_resume(dev);
>  
>  	i915_restore_state(dev);
>  	intel_opregion_setup(dev_priv);
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 1ec523d29789..e73c0fc84c73 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -3384,6 +3384,7 @@ void i915_gem_init_swizzling(struct drm_device *dev);
>  void i915_gem_cleanup_engines(struct drm_device *dev);
>  int __must_check i915_gem_wait_for_idle(struct drm_i915_private *dev_priv);
>  int __must_check i915_gem_suspend(struct drm_device *dev);
> +void i915_gem_resume(struct drm_device *dev);
>  void __i915_add_request(struct drm_i915_gem_request *req,
>  			struct drm_i915_gem_object *batch_obj,
>  			bool flush_caches);
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index cf0e8aa8035c..8b42a5101f11 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -4974,6 +4974,35 @@ i915_gem_stop_engines(struct drm_device *dev)
>  		dev_priv->gt.stop_engine(engine);
>  }
>  
> +static int switch_to_kernel_context(struct drm_i915_private *dev_priv)
> +{
> +	struct intel_engine_cs *engine;
> +
> +	for_each_engine(engine, dev_priv) {
> +		struct drm_i915_gem_request *req;
> +		int ret;
> +
> +		if (engine->last_context == NULL)
> +			continue;
> +
> +		if (engine->last_context == dev_priv->kernel_context)
> +			continue;
> +
> +		req = i915_gem_request_alloc(engine, dev_priv->kernel_context);
> +		if (IS_ERR(req))
> +			return PTR_ERR(req);
> +
> +		ret = 0;
> +		if (!i915.enable_execlists)
> +			ret = i915_switch_context(req);
> +		i915_add_request_no_flush(req);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +

Why do you want keep this separate? Altho the evict one is a little
bit different and as I didn't see any perf implications: Why not
consolidate the evict one and this one and have i915_gem_idle which
would park to default and wait for idle.

Other than that, this all looks fine.

-Mika



>  int
>  i915_gem_suspend(struct drm_device *dev)
>  {
> @@ -4983,6 +5012,10 @@ i915_gem_suspend(struct drm_device *dev)
>  	intel_suspend_gt_powersave(dev_priv);
>  
>  	mutex_lock(&dev->struct_mutex);
> +	ret = switch_to_kernel_context(dev_priv);
> +	if (ret)
> +		goto err;
> +
>  	ret = i915_gem_wait_for_idle(dev_priv);
>  	if (ret)
>  		goto err;
> @@ -5009,6 +5042,19 @@ err:
>  	return ret;
>  }
>  
> +void i915_gem_resume(struct drm_device *dev)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +
> +	mutex_lock(&dev->struct_mutex);
> +
> +	if (i915.enable_execlists)
> +		intel_lr_context_reset(dev_priv, dev_priv->kernel_context);
> +
> +	i915_gem_restore_gtt_mappings(dev);
> +	mutex_unlock(&dev->struct_mutex);
> +}
> +
>  void i915_gem_init_swizzling(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(dev);
> -- 
> 2.8.1
>
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