[PATCH i915 v3 1/2] i915: wait for fences in mmio_flip()

[Alexander Goins]

Okay, implemented these suggestions. Will send out v4 patch set once the crtc->primary->fb thing is cleared up.

-----Original Message-----
From: Chris Wilson [mailto:chris at chris-wilson.co.uk] 
Sent: Friday, November 13, 2015 2:08 AM
To: Alexander Goins
Cc: dri-devel at lists.freedesktop.org; daniel at fooishbar.org; daniel at ffwll.ch; maarten.lankhorst at linux.intel.com
Subject: Re: [PATCH i915 v3 1/2] i915: wait for fences in mmio_flip()

On Thu, Nov 12, 2015 at 05:49:28PM -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 at nvidia.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c 
> b/drivers/gpu/drm/i915/intel_display.c
> index b2270d5..acec108a 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[] = { @@ -11170,10 +11172,19 @@ 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 drm_i915_gem_object *pending_flip_obj =
> +		intel_crtc->unpin_work->pending_flip_obj;
>  	u32 start_vbl_count;
>  
>  	intel_mark_page_flip_active(intel_crtc);
>  
> +	/* For framebuffer backed by dmabuf, wait for fence */
> +	if (pending_flip_obj->base.dma_buf) {
> +		reservation_object_wait_timeout_rcu(
> +			pending_flip_obj->base.dma_buf->resv,
> +			true, false, msecs_to_jiffies(96));
> +	}

This wait should be prior to marking the flip as waiting for the flip-completion interrupt. My personal preference (aside from putting this next to the other wait) would to have been to use crtc->primary->fb to match the do_mmip_flips funcs (I expect that we will eliminate the pending_flip_obj in the near future).

Also we are missing the addition of
if (obj->base.dma_buf && obj->base.dma_buf->resv->fence_excl)
  return true;
to use_mmio_flip().
-Chris

--
Chris Wilson, Intel Open Source Technology Centre