[Intel-gfx] [PATCH 6/6] drm/i915: Wrap the preallocated BIOS framebuffer and preserve for KMS fbcon v12

[Jesse Barnes]

On Wed, 12 Feb 2014 23:07:15 +0000
Chris Wilson <chris at chris-wilson.co.uk> wrote:

> On Wed, Feb 12, 2014 at 12:26:29PM -0800, Jesse Barnes wrote:
> > +	/* Find the largest fb */
> > +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> > +		intel_crtc = to_intel_crtc(crtc);
> > +
> > +		if (!intel_crtc->active || !intel_crtc->plane_config.fb) {
> > +			DRM_DEBUG_KMS("pipe %c not active or no fb, skipping\n",
> > +				      pipe_name(intel_crtc->pipe));
> > +			continue;
> > +		}
> > +
> > +		if (intel_crtc->plane_config.size > max_size) {
> > +			DRM_DEBUG_KMS("found possible fb from plane %c\n",
> > +				      pipe_name(intel_crtc->pipe));
> > +			plane_config = &intel_crtc->plane_config;
> > +			fb = plane_config->fb;
> > +			max_size = plane_config->size;
> > +		}
> > +	}
> 
> I had another idea... Can you select the fb with offset 0 first and see
> if that fits every pipe? That way we reduce the potential fragmentation
> from the permanently pinned in-aperture object.

So if they happen to be the same size we'll prefer the one at 0?  I
guess we can tweak this all sorts of ways...  but we'll generally
probably only have a single buffer from the BIOS, so I'm not sure it'll
make much difference in practice.

> > +
> > +	if (!fb) {
> > +		DRM_DEBUG_KMS("no active fbs found, not using BIOS config\n");
> > +		goto out;
> > +	}
> > +
> > +	/* Now make sure all the pipes will fit into it */
> > +	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
> > +		unsigned int cur_size;
> > +
> > +		intel_crtc = to_intel_crtc(crtc);
> > +
> > +		if (!intel_crtc->active) {
> > +			DRM_DEBUG_KMS("pipe %c not active, skipping\n",
> > +				      pipe_name(intel_crtc->pipe));
> > +			continue;
> > +		}
> > +
> > +		DRM_DEBUG_KMS("checking plane %c for BIOS fb\n",
> > +			      pipe_name(intel_crtc->pipe));
> > +
> > +		/*
> > +		 * See if the plane fb we found above will fit on this
> > +		 * pipe.  Note we need to use the selected fb's bpp rather
> > +		 * than the current pipe's, since they could be different.
> > +		 */
> > +		cur_size = intel_crtc->config.adjusted_mode.crtc_hdisplay *
> > +			intel_crtc->config.adjusted_mode.crtc_vdisplay;
> > +		DRM_DEBUG_KMS("pipe %c area: %d\n", pipe_name(intel_crtc->pipe),
> > +			      cur_size);
> > +		cur_size *= fb->base.bits_per_pixel / 8;
> > +		DRM_DEBUG_KMS("total size %d (bpp %d)\n", cur_size,
> > +			      fb->base.bits_per_pixel / 8);
> 
> But the display hardware will be using the stride from the fb, so the
> end of the last row will still be vdisplay*fb->stride, right? Unless the
> fb pitch itself is recomputed to match?

I think there are two cases:
  1) pipe A re-uses plane A's fb - no changes needed, should match
     nicely
  2) pipe B switches to plane A's fb - we'll end up doing a set_base and
     switching the stride bits and depth over to the plane A fb params,
     so it should work
right?

-- 
Jesse Barnes, Intel Open Source Technology Center