Re: [PATCH v2 1/3] drm/i915/frontbuffer: Pull frontbuffer_flush out of gem_obj_pin_to_display

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Wed, Mar 07, 2018 at 10:54:28PM +0000, Pandiyan, Dhinakaran wrote:
> 
> 
> 
> On Wed, 2018-03-07 at 14:46 -0800, Rodrigo Vivi wrote:
> > On Tue, Mar 06, 2018 at 07:34:18PM -0800, Dhinakaran Pandiyan wrote:
> > > From: "Pandiyan, Dhinakaran" <dhinakaran.pandiyan@intel.com>
> > > 
> > > i915_gem_obj_pin_to_display() calls frontbuffer_flush with origin set to
> > > DIRTYFB. The callers however are at a vantage point to decide if hardware
> > > frontbuffer tracking can do the flush for us. For example, legacy cursor
> > > updates, like flips, write to MMIO registers, which then triggers PSR flush
> > > by the hardware. Moving frontbuffer_flush out will enable us to skip a
> > > software initiated flush by setting origin to FLIP. Thanks to Chris for the
> > > idea.
> > > 
> > > v2:
> > > Rebased due to Ville adding intel_plane_pin_fb().
> > > Minor code reordering as fb_obj_flush doesn't need struct_mutex (Chris)
> > > 
> > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> > > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_gem.c      | 9 ++++-----
> > >  drivers/gpu/drm/i915/intel_display.c | 9 +++++++--
> > >  drivers/gpu/drm/i915/intel_fbdev.c   | 5 +++--
> > >  drivers/gpu/drm/i915/intel_overlay.c | 1 +
> > >  4 files changed, 15 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > > index a5bd07338b46..e4c5a1a22d8b 100644
> > > --- a/drivers/gpu/drm/i915/i915_gem.c
> > > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > > @@ -4071,9 +4071,10 @@ int i915_gem_set_caching_ioctl(struct drm_device *dev, void *data,
> > >  }
> > >  
> > >  /*
> > > - * Prepare buffer for display plane (scanout, cursors, etc).
> > > - * Can be called from an uninterruptible phase (modesetting) and allows
> > > - * any flushes to be pipelined (for pageflips).
> > > + * Prepare buffer for display plane (scanout, cursors, etc). Can be called from
> > > + * an uninterruptible phase (modesetting) and allows any flushes to be pipelined
> > > + * (for pageflips). We only flush the caches while preparing the buffer for
> > > + * display, the callers are responsible for frontbuffer flush.
> > >   */
> > >  struct i915_vma *
> > >  i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> > > @@ -4129,9 +4130,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> > >  
> > >  	vma->display_alignment = max_t(u64, vma->display_alignment, alignment);
> > >  
> > > -	/* Treat this as an end-of-frame, like intel_user_framebuffer_dirty() */
> > 
> > Although flush by some definition here is invalidate + flush
> > I see flush operations as the operation to be performed at the "end-of-frame".
> > After the operation was done and whatever had to be modified was modified.
> > 
> > I see you patch changing the flush to the creation and begin of the fb handling
> > like on creating and init fb functions. I believe by that time we are not ready
> > to exit PSR yet.
> > 
> > What am I missing?
> 
> 
> The functions that you are referring to call
> i915_gem_object_pin_to_display_plane() which in turn calls frontbuffer
> flush. This patch is just a refactor, doesn't change whether flush() is
> called. I am trying to move it up the call stack so that flush() can be
> selectively removed depending on the call site.

Oh! now it made more sense...

probably this phrase is more clear than the current commit message for a
commit message.

But I checked the code and I agree it is right, so:

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>



> 
> 
> 
> 
> > 
> > >  	__i915_gem_object_flush_for_display(obj);
> > > -	intel_fb_obj_flush(obj, ORIGIN_DIRTYFB);
> > >  
> > >  	/* It should now be out of any other write domains, and we can update
> > >  	 * the domain values for our changes.
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > > index 331084082545..91ce8a0522a3 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -2858,6 +2858,9 @@ intel_find_initial_plane_obj(struct intel_crtc *intel_crtc,
> > >  		return;
> > >  	}
> > >  
> > > +	obj = intel_fb_obj(fb);
> > > +	intel_fb_obj_flush(obj, ORIGIN_DIRTYFB);
> > > +
> > >  	plane_state->src_x = 0;
> > >  	plane_state->src_y = 0;
> > >  	plane_state->src_w = fb->width << 16;
> > > @@ -2871,7 +2874,6 @@ intel_find_initial_plane_obj(struct intel_crtc *intel_crtc,
> > >  	intel_state->base.src = drm_plane_state_src(plane_state);
> > >  	intel_state->base.dst = drm_plane_state_dest(plane_state);
> > >  
> > > -	obj = intel_fb_obj(fb);
> > >  	if (i915_gem_object_is_tiled(obj))
> > >  		dev_priv->preserve_bios_swizzle = true;
> > >  
> > > @@ -12785,6 +12787,8 @@ intel_prepare_plane_fb(struct drm_plane *plane,
> > >  	if (ret)
> > >  		return ret;
> > >  
> > > +	intel_fb_obj_flush(obj, ORIGIN_DIRTYFB);
> > > +
> > >  	if (!new_state->fence) { /* implicit fencing */
> > >  		struct dma_fence *fence;
> > >  
> > > @@ -13172,8 +13176,9 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> > >  	if (ret)
> > >  		goto out_unlock;
> > >  
> > > -	old_fb = old_plane_state->fb;
> > > +	intel_fb_obj_flush(intel_fb_obj(fb), ORIGIN_DIRTYFB);
> > >  
> > > +	old_fb = old_plane_state->fb;
> > >  	i915_gem_track_fb(intel_fb_obj(old_fb), intel_fb_obj(fb),
> > >  			  intel_plane->frontbuffer_bit);
> > >  
> > > diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> > > index 6f12adc06365..65a3313723c9 100644
> > > --- a/drivers/gpu/drm/i915/intel_fbdev.c
> > > +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> > > @@ -221,6 +221,9 @@ static int intelfb_create(struct drm_fb_helper *helper,
> > >  		goto out_unlock;
> > >  	}
> > >  
> > > +	fb = &ifbdev->fb->base;
> > > +	intel_fb_obj_flush(intel_fb_obj(fb), ORIGIN_DIRTYFB);
> > > +
> > >  	info = drm_fb_helper_alloc_fbi(helper);
> > >  	if (IS_ERR(info)) {
> > >  		DRM_ERROR("Failed to allocate fb_info\n");
> > > @@ -230,8 +233,6 @@ static int intelfb_create(struct drm_fb_helper *helper,
> > >  
> > >  	info->par = helper;
> > >  
> > > -	fb = &ifbdev->fb->base;
> > > -
> > >  	ifbdev->helper.fb = fb;
> > >  
> > >  	strcpy(info->fix.id, "inteldrmfb");
> > > diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c
> > > index 36671a937fa4..c2f10d899329 100644
> > > --- a/drivers/gpu/drm/i915/intel_overlay.c
> > > +++ b/drivers/gpu/drm/i915/intel_overlay.c
> > > @@ -807,6 +807,7 @@ static int intel_overlay_do_put_image(struct intel_overlay *overlay,
> > >  		ret = PTR_ERR(vma);
> > >  		goto out_pin_section;
> > >  	}
> > > +	intel_fb_obj_flush(new_bo, ORIGIN_DIRTYFB);
> > >  
> > >  	ret = i915_vma_put_fence(vma);
> > >  	if (ret)
> > > -- 
> > > 2.14.1
> > > 
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