Re: [PATCH 2/2] drm/i915: Drop reference to plane state wait req in destructor.

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Aug 09, 2016 at 12:15:51PM +0200, Maarten Lankhorst wrote:
> With gem requests reworked to only keep some memory around after
> it's completed it's now mostly harmless to keep a reference to the
> request until the state is destroyed. This makes it easy to hang
> on to the request until the plane state is destroyed since it is
> just a bunch of memory now.
> 
> On my 64-bits system a i915_gem_request is 352 bytes. With all
> 3 crtc's, each 4 planes enabled the total is 4224 bytes,
> low enough not to optimize this case too much.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Keith Packard <keithp@keithp.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: David Airlie <airlied@linux.ie>
> Cc: intel-gfx@lists.freedesktop.org
> Cc: dri-devel@lists.freedesktop.org
> Fixes: 849782575325 ("drm/i915: cleanup_plane_fb: also drop reference to current state wait_req")

Yeah, I think hanging onto requests like that is perfectly fine, and it
simplifies the gymnastics for tracking things if we always allocate
drm_*_state resources in atomic_duplicate, update the refs in atomic_check
(with the various set functions the core has, or our own) and then release
references in atomic_state destroy.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/intel_atomic_plane.c | 5 ++++-
>  drivers/gpu/drm/i915/intel_display.c      | 6 ------
>  2 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_atomic_plane.c b/drivers/gpu/drm/i915/intel_atomic_plane.c
> index 7de7721f65bc..f98071a1dcc0 100644
> --- a/drivers/gpu/drm/i915/intel_atomic_plane.c
> +++ b/drivers/gpu/drm/i915/intel_atomic_plane.c
> @@ -101,7 +101,10 @@ void
>  intel_plane_destroy_state(struct drm_plane *plane,
>  			  struct drm_plane_state *state)
>  {
> -	WARN_ON(state && to_intel_plane_state(state)->wait_req);
> +	struct intel_plane_state *intel_state = to_intel_plane_state(state);
> +
> +	i915_gem_request_assign(&intel_state->wait_req, NULL);
> +
>  	drm_atomic_helper_plane_destroy_state(plane, state);
>  }
>  
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index af45ee206239..774895288bcc 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -14063,17 +14063,11 @@ intel_cleanup_plane_fb(struct drm_plane *plane,
>  		       const struct drm_plane_state *old_state)
>  {
>  	struct drm_device *dev = plane->dev;
> -	struct intel_plane_state *intel_state = to_intel_plane_state(plane->state);
>  	struct drm_i915_gem_object *old_obj = intel_fb_obj(old_state->fb);
> -	struct intel_plane_state *old_intel_state =
> -		to_intel_plane_state(old_state);
>  
>  	if (old_obj && (plane->type != DRM_PLANE_TYPE_CURSOR ||
>  	    !INTEL_INFO(dev)->cursor_needs_physical))
>  		intel_unpin_fb_obj(old_state->fb, old_state->rotation);
> -
> -	i915_gem_request_assign(&intel_state->wait_req, NULL);
> -	i915_gem_request_assign(&old_intel_state->wait_req, NULL);
>  }
>  
>  int
> -- 
> 2.7.4
> 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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