On ti, 2015-03-31 at 13:55 +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> Purpose of this tracking is to know when to flush the cache between
> the CPU and the non-coherent display engine. Prior to:
>
> commit 121920faf2ccce9aa66a7e2588415c9647b66104
> Author: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Date: Mon Mar 23 11:10:37 2015 +0000
>
> drm/i915/skl: Query display address through a wrapper
>
> This worked by a mix of direct flag manipulation and checking for
> existence of a pinned GGTT VMA.
>
> With the introduction of rotated display mappings this approach is
> no longer correct.
>
> New simpler approach is to just keep this count over calls which pin
> and unpin objects to and from display, at the slight cost of extra
> space in every bo.
>
> (Inspired and extracted code from a larger rework by Chris Wilson.)
>
> v2: Remove the limit since it is not well defined. (Chris Wilson, Ville Syrjälä)
> v3: Commit message corrections. (Chris Wilson)
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 3 ++-
> drivers/gpu/drm/i915/i915_gem.c | 30 ++++++------------------------
> 2 files changed, 8 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 4ef320c..37abd58 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1969,7 +1969,6 @@ struct drm_i915_gem_object {
> */
> unsigned int fault_mappable:1;
> unsigned int pin_mappable:1;
> - unsigned int pin_display:1;
>
> /*
> * Is the object to be mapped as read-only to the GPU
> @@ -1983,6 +1982,8 @@ struct drm_i915_gem_object {
>
> unsigned int frontbuffer_bits:INTEL_FRONTBUFFER_BITS;
>
> + unsigned int pin_display;
> +
Here. Comment below.
> struct sg_table *pages;
> int pages_pin_count;
>
How about naming it like the variable just below it (pages_pin_count).
So let it be "display_pin_count", and make it just "int" too, I don't
think the 1 bit reduction in pin count matters really, but having sign
makes it useful for detecting negative pin count errors? At least I'd
make it signed integer and make some of the spots WARN_ON(xxx--- < 0).
Regards, Joonas
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 3a91365..8b75dab 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3849,24 +3849,6 @@ unlock:
> return ret;
> }
>
> -static bool is_pin_display(struct drm_i915_gem_object *obj)
> -{
> - struct i915_vma *vma;
> -
> - vma = i915_gem_obj_to_ggtt(obj);
> - if (!vma)
> - return false;
> -
> - /* There are 2 sources that pin objects:
> - * 1. The display engine (scanouts, sprites, cursors);
> - * 2. Reservations for execbuffer;
> - *
> - * We can ignore reservations as we hold the struct_mutex and
> - * are only called outside of the reservation path.
> - */
> - return vma->pin_count;
> -}
> -
> /*
> * Prepare buffer for display plane (scanout, cursors, etc).
> * Can be called from an uninterruptible phase (modesetting) and allows
> @@ -3879,7 +3861,6 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> const struct i915_ggtt_view *view)
> {
> u32 old_read_domains, old_write_domain;
> - bool was_pin_display;
> int ret;
>
> if (pipelined != i915_gem_request_get_ring(obj->last_read_req)) {
> @@ -3891,8 +3872,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> /* Mark the pin_display early so that we account for the
> * display coherency whilst setting up the cache domains.
> */
> - was_pin_display = obj->pin_display;
> - obj->pin_display = true;
> + obj->pin_display++;
>
> /* The display engine is not coherent with the LLC cache on gen6. As
> * a result, we make sure that the pinning that is about to occur is
> @@ -3936,8 +3916,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> return 0;
>
> err_unpin_display:
> - WARN_ON(was_pin_display != is_pin_display(obj));
> - obj->pin_display = was_pin_display;
> + obj->pin_display--;
> return ret;
> }
>
> @@ -3945,9 +3924,12 @@ void
> i915_gem_object_unpin_from_display_plane(struct drm_i915_gem_object *obj,
> const struct i915_ggtt_view *view)
> {
> + if (WARN_ON(obj->pin_display == 0))
> + return;
> +
> i915_gem_object_ggtt_unpin_view(obj, view);
>
> - obj->pin_display = is_pin_display(obj);
> + obj->pin_display--;
> }
>
> int
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