Re: [RFC 04/39] drm/i915: Prelude to splitting i915_gem_do_execbuffer in two

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jul 17, 2015 at 03:33:13PM +0100, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
> 
> The scheduler decouples the submission of batch buffers to the driver with their
> submission to the hardware. This basically means splitting the execbuffer()
> function in half. This change rearranges some code ready for the split to occur.

Would be nice to explain what and why moves so reviewers don't have to
reverse-engineer the idea behind this patch.

> 
> Change-Id: Icc9c8afaac18821f3eb8a151a49f918f90c068a3
> For: VIZ-1587
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>

Moving move_to_active around is really scary and should be a separate
patch. The reasons it is where it currently is is that move_to_active is
somewhat destructive and can't be undone. Hence why it is past the point
of no return.

Also why can't we just pull this out into generic code?
-Daniel


> ---
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c | 57 ++++++++++++++++++------------
>  drivers/gpu/drm/i915/intel_lrc.c           | 18 +++++++---
>  2 files changed, 47 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index d95d472..988ecd4 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -926,10 +926,7 @@ i915_gem_execbuffer_move_to_gpu(struct drm_i915_gem_request *req,
>  	if (flush_domains & I915_GEM_DOMAIN_GTT)
>  		wmb();
>  
> -	/* Unconditionally invalidate gpu caches and ensure that we do flush
> -	 * any residual writes from the previous batch.
> -	 */
> -	return intel_ring_invalidate_all_caches(req);
> +	return 0;
>  }
>  
>  static bool
> @@ -1253,17 +1250,6 @@ i915_gem_ringbuffer_submission(struct i915_execbuffer_params *params,
>  		}
>  	}
>  
> -	ret = i915_gem_execbuffer_move_to_gpu(params->request, vmas);
> -	if (ret)
> -		goto error;
> -
> -	ret = i915_switch_context(params->request);
> -	if (ret)
> -		goto error;
> -
> -	WARN(params->ctx->ppgtt && params->ctx->ppgtt->pd_dirty_rings & (1<<ring->id),
> -	     "%s didn't clear reload\n", ring->name);
> -
>  	instp_mode = args->flags & I915_EXEC_CONSTANTS_MASK;
>  	instp_mask = I915_EXEC_CONSTANTS_MASK;
>  	switch (instp_mode) {
> @@ -1301,6 +1287,32 @@ i915_gem_ringbuffer_submission(struct i915_execbuffer_params *params,
>  		goto error;
>  	}
>  
> +	ret = i915_gem_execbuffer_move_to_gpu(params->request, vmas);
> +	if (ret)
> +		goto error;
> +
> +	i915_gem_execbuffer_move_to_active(vmas, params->request);
> +
> +	/* To be split into two functions here... */
> +
> +	intel_runtime_pm_get(dev_priv);
> +
> +	/*
> +	 * Unconditionally invalidate gpu caches and ensure that we do flush
> +	 * any residual writes from the previous batch.
> +	 */
> +	ret = intel_ring_invalidate_all_caches(params->request);
> +	if (ret)
> +		goto error;
> +
> +	/* Switch to the correct context for the batch */
> +	ret = i915_switch_context(params->request);
> +	if (ret)
> +		goto error;
> +
> +	WARN(params->ctx->ppgtt && params->ctx->ppgtt->pd_dirty_rings & (1<<ring->id),
> +	     "%s didn't clear reload\n", ring->name);
> +
>  	if (ring == &dev_priv->ring[RCS] &&
>  			instp_mode != dev_priv->relative_constants_mode) {
>  		ret = intel_ring_begin(params->request, 4);
> @@ -1344,15 +1356,20 @@ i915_gem_ringbuffer_submission(struct i915_execbuffer_params *params,
>  						exec_start, exec_len,
>  						params->dispatch_flags);
>  		if (ret)
> -			return ret;
> +			goto error;
>  	}
>  
>  	trace_i915_gem_ring_dispatch(params->request, params->dispatch_flags);
>  
> -	i915_gem_execbuffer_move_to_active(vmas, params->request);
>  	i915_gem_execbuffer_retire_commands(params);
>  
>  error:
> +	/*
> +	 * intel_gpu_busy should also get a ref, so it will free when the device
> +	 * is really idle.
> +	 */
> +	intel_runtime_pm_put(dev_priv);
> +
>  	kfree(cliprects);
>  	return ret;
>  }
> @@ -1563,8 +1580,6 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
>  	}
>  #endif
>  
> -	intel_runtime_pm_get(dev_priv);
> -
>  	ret = i915_mutex_lock_interruptible(dev);
>  	if (ret)
>  		goto pre_mutex_err;
> @@ -1759,10 +1774,6 @@ err:
>  	mutex_unlock(&dev->struct_mutex);
>  
>  pre_mutex_err:
> -	/* intel_gpu_busy should also get a ref, so it will free when the device
> -	 * is really idle. */
> -	intel_runtime_pm_put(dev_priv);
> -
>  	if (fd_fence_complete != -1) {
>  		sys_close(fd_fence_complete);
>  		args->rsvd2 = (__u64) -1;
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 8aa9a18..89f3bcd 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -613,10 +613,7 @@ static int execlists_move_to_gpu(struct drm_i915_gem_request *req,
>  	if (flush_domains & I915_GEM_DOMAIN_GTT)
>  		wmb();
>  
> -	/* Unconditionally invalidate gpu caches and ensure that we do flush
> -	 * any residual writes from the previous batch.
> -	 */
> -	return logical_ring_invalidate_all_caches(req);
> +	return 0;
>  }
>  
>  int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request)
> @@ -889,6 +886,18 @@ int intel_execlists_submission(struct i915_execbuffer_params *params,
>  	if (ret)
>  		return ret;
>  
> +	i915_gem_execbuffer_move_to_active(vmas, params->request);
> +
> +	/* To be split into two functions here... */
> +
> +	/*
> +	 * Unconditionally invalidate gpu caches and ensure that we do flush
> +	 * any residual writes from the previous batch.
> +	 */
> +	ret = logical_ring_invalidate_all_caches(params->request);
> +	if (ret)
> +		return ret;
> +
>  	if (ring == &dev_priv->ring[RCS] &&
>  	    instp_mode != dev_priv->relative_constants_mode) {
>  		ret = intel_logical_ring_begin(params->request, 4);
> @@ -913,7 +922,6 @@ int intel_execlists_submission(struct i915_execbuffer_params *params,
>  
>  	trace_i915_gem_ring_dispatch(params->request, params->dispatch_flags);
>  
> -	i915_gem_execbuffer_move_to_active(vmas, params->request);
>  	i915_gem_execbuffer_retire_commands(params);
>  
>  	return 0;
> -- 
> 1.9.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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