Re: [Intel-gfx] [PATCH v3] drm/i915/display: Use dma_fence interfaces instead of i915_sw_fence

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Oct 30, 2023 at 02:09:15PM +0200, Jouni Högander wrote:
> We are preparing for Xe driver. Xe driver doesn't have i915_sw_fence
> implementation. Lets drop i915_sw_fence usage from display code and
> use dma_fence interfaces directly.
> 
> For this purpose stack dma fences from related objects into new plane
> state. Drm_gem_plane_helper_prepare_fb can be used for fences in new
> fb. Separate local implementation is used for Stacking fences from old fb
> into new plane state. Then wait for these stacked fences during atomic
> commit. There is no be need for separate GPU reset handling in
> intel_atomic_commit_fence_wait as the fences are signaled when GPU hang is
> detected and GPU is being reset.
> 
> v3:
>   - Rename add_fences and it's parameters
>   - Remove signaled check
>   - Remove waiting old_plane_state fences
> v2:
>   - Add fences from old fb into new_plane_state->uapi.fence rather than
>     into old_plane_state->uapi.fence
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: José Roberto de Souza <jose.souza@intel.com>
> 
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_atomic.c   |  3 -
>  .../gpu/drm/i915/display/intel_atomic_plane.c | 86 +++++++++++--------
>  drivers/gpu/drm/i915/display/intel_display.c  | 68 +++------------
>  .../drm/i915/display/intel_display_types.h    |  2 -
>  4 files changed, 64 insertions(+), 95 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
> index 5d18145da279..ec0d5168b503 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic.c
> +++ b/drivers/gpu/drm/i915/display/intel_atomic.c
> @@ -331,9 +331,6 @@ void intel_atomic_state_free(struct drm_atomic_state *_state)
>  
>  	drm_atomic_state_default_release(&state->base);
>  	kfree(state->global_objs);
> -
> -	i915_sw_fence_fini(&state->commit_ready);
> -
>  	kfree(state);
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> index b1074350616c..d7a2d7ff6090 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> +++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> @@ -31,7 +31,10 @@
>   * prepare/check/commit/cleanup steps.
>   */
>  
> +#include <linux/dma-fence-chain.h>
> +
>  #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_gem_atomic_helper.h>
>  #include <drm/drm_blend.h>
>  #include <drm/drm_fourcc.h>
>  
> @@ -1012,6 +1015,44 @@ int intel_plane_check_src_coordinates(struct intel_plane_state *plane_state)
>  	return 0;
>  }
>  
> +static int add_dma_resv_fences_to_new_plane_state(struct dma_resv *resv,
> +						  struct drm_plane_state *new_plane_state)

The 'to_new_plane_state' part in the name seems a bit redundant.

> +{
> +	struct dma_fence *fence = dma_fence_get(new_plane_state->fence);
> +	enum dma_resv_usage usage;
> +	struct dma_fence *new;
> +	int ret;
> +
> +	usage = fence ? DMA_RESV_USAGE_KERNEL : DMA_RESV_USAGE_WRITE;

I believe we want USAGE_WRITE here always. We aren't attempting
to make the regular implicit vs. explicit sync decision here.

Apart from that everything else looks good to me. So with that
sorted this is
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> +
> +	ret = dma_resv_get_singleton(resv, usage, &new);
> +	if (ret)
> +		goto error;
> +
> +	if (new && fence) {
> +		struct dma_fence_chain *chain = dma_fence_chain_alloc();
> +
> +		if (!chain) {
> +			ret = -ENOMEM;
> +			goto error;
> +		}
> +
> +		dma_fence_chain_init(chain, fence, new, 1);
> +		fence = &chain->base;
> +
> +	} else if (new) {
> +		fence = new;
> +	}
> +
> +	dma_fence_put(new_plane_state->fence);
> +	new_plane_state->fence = fence;
> +	return 0;
> +
> +error:
> +	dma_fence_put(fence);
> +	return ret;
> +}
> +
>  /**
>   * intel_prepare_plane_fb - Prepare fb for usage on plane
>   * @_plane: drm plane to prepare for
> @@ -1035,7 +1076,7 @@ intel_prepare_plane_fb(struct drm_plane *_plane,
>  	struct intel_atomic_state *state =
>  		to_intel_atomic_state(new_plane_state->uapi.state);
>  	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
> -	const struct intel_plane_state *old_plane_state =
> +	struct intel_plane_state *old_plane_state =
>  		intel_atomic_get_old_plane_state(state, plane);
>  	struct drm_i915_gem_object *obj = intel_fb_obj(new_plane_state->hw.fb);
>  	struct drm_i915_gem_object *old_obj = intel_fb_obj(old_plane_state->hw.fb);
> @@ -1058,55 +1099,28 @@ intel_prepare_plane_fb(struct drm_plane *_plane,
>  		 * can safely continue.
>  		 */
>  		if (new_crtc_state && intel_crtc_needs_modeset(new_crtc_state)) {
> -			ret = i915_sw_fence_await_reservation(&state->commit_ready,
> -							      old_obj->base.resv,
> -							      false, 0,
> -							      GFP_KERNEL);
> +			ret = add_dma_resv_fences_to_new_plane_state(old_obj->base.resv,
> +								     &new_plane_state->uapi);
>  			if (ret < 0)
>  				return ret;
>  		}
>  	}
>  
> -	if (new_plane_state->uapi.fence) { /* explicit fencing */
> -		i915_gem_fence_wait_priority(new_plane_state->uapi.fence,
> -					     &attr);
> -		ret = i915_sw_fence_await_dma_fence(&state->commit_ready,
> -						    new_plane_state->uapi.fence,
> -						    i915_fence_timeout(dev_priv),
> -						    GFP_KERNEL);
> -		if (ret < 0)
> -			return ret;
> -	}
> -
>  	if (!obj)
>  		return 0;
>  
> -
>  	ret = intel_plane_pin_fb(new_plane_state);
>  	if (ret)
>  		return ret;
>  
> -	i915_gem_object_wait_priority(obj, 0, &attr);
> +	ret = drm_gem_plane_helper_prepare_fb(&plane->base, &new_plane_state->uapi);
> +	if (ret < 0)
> +		goto unpin_fb;
>  
> -	if (!new_plane_state->uapi.fence) { /* implicit fencing */
> -		struct dma_resv_iter cursor;
> -		struct dma_fence *fence;
> -
> -		ret = i915_sw_fence_await_reservation(&state->commit_ready,
> -						      obj->base.resv, false,
> -						      i915_fence_timeout(dev_priv),
> -						      GFP_KERNEL);
> -		if (ret < 0)
> -			goto unpin_fb;
> +	if (new_plane_state->uapi.fence) {
> +		i915_gem_fence_wait_priority(new_plane_state->uapi.fence,
> +					     &attr);
>  
> -		dma_resv_iter_begin(&cursor, obj->base.resv,
> -				    DMA_RESV_USAGE_WRITE);
> -		dma_resv_for_each_fence_unlocked(&cursor, fence) {
> -			intel_display_rps_boost_after_vblank(new_plane_state->hw.crtc,
> -							     fence);
> -		}
> -		dma_resv_iter_end(&cursor);
> -	} else {
>  		intel_display_rps_boost_after_vblank(new_plane_state->hw.crtc,
>  						     new_plane_state->uapi.fence);
>  	}
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 1caf46e3e569..6a37573c3d82 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -48,6 +48,7 @@
>  #include "g4x_dp.h"
>  #include "g4x_hdmi.h"
>  #include "hsw_ips.h"
> +#include "i915_config.h"
>  #include "i915_drv.h"
>  #include "i915_reg.h"
>  #include "i915_utils.h"
> @@ -7056,29 +7057,22 @@ void intel_atomic_helper_free_state_worker(struct work_struct *work)
>  
>  static void intel_atomic_commit_fence_wait(struct intel_atomic_state *intel_state)
>  {
> -	struct wait_queue_entry wait_fence, wait_reset;
> -	struct drm_i915_private *dev_priv = to_i915(intel_state->base.dev);
> -
> -	init_wait_entry(&wait_fence, 0);
> -	init_wait_entry(&wait_reset, 0);
> -	for (;;) {
> -		prepare_to_wait(&intel_state->commit_ready.wait,
> -				&wait_fence, TASK_UNINTERRUPTIBLE);
> -		prepare_to_wait(bit_waitqueue(&to_gt(dev_priv)->reset.flags,
> -					      I915_RESET_MODESET),
> -				&wait_reset, TASK_UNINTERRUPTIBLE);
> -
> +	struct drm_i915_private *i915 = to_i915(intel_state->base.dev);
> +	struct drm_plane *plane;
> +	struct drm_plane_state *new_plane_state;
> +	int ret, i;
>  
> -		if (i915_sw_fence_done(&intel_state->commit_ready) ||
> -		    test_bit(I915_RESET_MODESET, &to_gt(dev_priv)->reset.flags))
> -			break;
> +	for_each_new_plane_in_state(&intel_state->base, plane, new_plane_state, i) {
> +		if (new_plane_state->fence) {
> +			ret = dma_fence_wait_timeout(new_plane_state->fence, false,
> +						     i915_fence_timeout(i915));
> +			if (ret <= 0)
> +				break;
>  
> -		schedule();
> +			dma_fence_put(new_plane_state->fence);
> +			new_plane_state->fence = NULL;
> +		}
>  	}
> -	finish_wait(&intel_state->commit_ready.wait, &wait_fence);
> -	finish_wait(bit_waitqueue(&to_gt(dev_priv)->reset.flags,
> -				  I915_RESET_MODESET),
> -		    &wait_reset);
>  }
>  
>  static void intel_atomic_cleanup_work(struct work_struct *work)
> @@ -7370,32 +7364,6 @@ static void intel_atomic_commit_work(struct work_struct *work)
>  	intel_atomic_commit_tail(state);
>  }
>  
> -static int
> -intel_atomic_commit_ready(struct i915_sw_fence *fence,
> -			  enum i915_sw_fence_notify notify)
> -{
> -	struct intel_atomic_state *state =
> -		container_of(fence, struct intel_atomic_state, commit_ready);
> -
> -	switch (notify) {
> -	case FENCE_COMPLETE:
> -		/* we do blocking waits in the worker, nothing to do here */
> -		break;
> -	case FENCE_FREE:
> -		{
> -			struct drm_i915_private *i915 = to_i915(state->base.dev);
> -			struct intel_atomic_helper *helper =
> -				&i915->display.atomic_helper;
> -
> -			if (llist_add(&state->freed, &helper->free_list))
> -				queue_work(i915->unordered_wq, &helper->free_work);
> -			break;
> -		}
> -	}
> -
> -	return NOTIFY_DONE;
> -}
> -
>  static void intel_atomic_track_fbs(struct intel_atomic_state *state)
>  {
>  	struct intel_plane_state *old_plane_state, *new_plane_state;
> @@ -7418,10 +7386,6 @@ int intel_atomic_commit(struct drm_device *dev, struct drm_atomic_state *_state,
>  
>  	state->wakeref = intel_runtime_pm_get(&dev_priv->runtime_pm);
>  
> -	drm_atomic_state_get(&state->base);
> -	i915_sw_fence_init(&state->commit_ready,
> -			   intel_atomic_commit_ready);
> -
>  	/*
>  	 * The intel_legacy_cursor_update() fast path takes care
>  	 * of avoiding the vblank waits for simple cursor
> @@ -7454,7 +7418,6 @@ int intel_atomic_commit(struct drm_device *dev, struct drm_atomic_state *_state,
>  	if (ret) {
>  		drm_dbg_atomic(&dev_priv->drm,
>  			       "Preparing state failed with %i\n", ret);
> -		i915_sw_fence_commit(&state->commit_ready);
>  		intel_runtime_pm_put(&dev_priv->runtime_pm, state->wakeref);
>  		return ret;
>  	}
> @@ -7470,8 +7433,6 @@ int intel_atomic_commit(struct drm_device *dev, struct drm_atomic_state *_state,
>  		struct intel_crtc *crtc;
>  		int i;
>  
> -		i915_sw_fence_commit(&state->commit_ready);
> -
>  		for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i)
>  			intel_color_cleanup_commit(new_crtc_state);
>  
> @@ -7485,7 +7446,6 @@ int intel_atomic_commit(struct drm_device *dev, struct drm_atomic_state *_state,
>  	drm_atomic_state_get(&state->base);
>  	INIT_WORK(&state->base.commit_work, intel_atomic_commit_work);
>  
> -	i915_sw_fence_commit(&state->commit_ready);
>  	if (nonblock && state->modeset) {
>  		queue_work(dev_priv->display.wq.modeset, &state->base.commit_work);
>  	} else if (nonblock) {
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 65ea37fe8cff..047fe3f8905a 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -676,8 +676,6 @@ struct intel_atomic_state {
>  
>  	bool rps_interactive;
>  
> -	struct i915_sw_fence commit_ready;
> -
>  	struct llist_node freed;
>  };
>  
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel