Re: [PATCH i915 v4 1/2] i915: wait for fences in mmio_flip()

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

On Thu, Nov 19, 2015 at 07:51:25PM -0800, Alex Goins wrote:
> If a buffer is backed by dmabuf, wait on its reservation object's fences
> before flipping.
> 
> Signed-off-by: Alex Goins <agoins@nvidia.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b2270d5..4867ff0 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -44,6 +44,8 @@
>  #include <drm/drm_plane_helper.h>
>  #include <drm/drm_rect.h>
>  #include <linux/dma_remapping.h>
> +#include <linux/reservation.h>
> +#include <linux/dma-buf.h>
>  
>  /* Primary plane formats for gen <= 3 */
>  static const uint32_t i8xx_primary_formats[] = {
> @@ -11088,6 +11090,8 @@ static bool use_mmio_flip(struct intel_engine_cs *ring,
>  		return true;
>  	else if (i915.enable_execlists)
>  		return true;
> +	else if (obj->base.dma_buf && obj->base.dma_buf->resv->fence_excl)
> +		return true;
>  	else
>  		return ring != i915_gem_request_get_ring(obj->last_write_req);
>  }
> @@ -11170,8 +11174,18 @@ static void ilk_do_mmio_flip(struct intel_crtc *intel_crtc)
>  static void intel_do_mmio_flip(struct intel_crtc *intel_crtc)
>  {
>  	struct drm_device *dev = intel_crtc->base.dev;
> +	struct intel_framebuffer *intel_fb =
> +		to_intel_framebuffer(intel_crtc->base.primary->fb);
> +	struct drm_i915_gem_object *obj = intel_fb->obj;
>  	u32 start_vbl_count;
>  
> +	/* For framebuffer backed by dmabuf, wait for fence */
> +	if (obj->base.dma_buf) {
> +		reservation_object_wait_timeout_rcu(
> +			obj->base.dma_buf->resv,
> +			false, true, MAX_SCHEDULE_TIMEOUT);
> +	}
> +

Why is this in do_mmio_flip() rather than next to the normal seqno wait
at the previous level?

>  	intel_mark_page_flip_active(intel_crtc);
>  
>  	intel_pipe_update_start(intel_crtc, &start_vbl_count);
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC
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