[Intel-gfx] [PATCH 3/3] drm/i915: Use intel_plane_obj_offset from more places

[Chris Wilson]

On Tue, Jun 16, 2015 at 02:32:40PM +0100, Tvrtko Ursulin wrote:
> 
> On 06/16/2015 12:48 PM, Chris Wilson wrote:
> >On Tue, Jun 16, 2015 at 12:31:23PM +0100, Tvrtko Ursulin wrote:
> >>That is partially correct, I do see it as problematic since I
> >>assumed someone will modeset with this fb/object at some point, and
> >>there will be state available then, which won't have the cached
> >>display address at all since the state is not present during fbdev
> >>setup.
> >>
> >>Does that never happens? I mean, the modeset with state using the
> >>fb/object prepared in intefb_alloc?
> >
> >No. The setup in intelfb_alloc is only concerned with generating a GGTT
> >mmapping that is consistent with later use by modesetting. The important
> >detail is to make sure the alignment is correct (or else the modeset
> >will fail as it cannot move the object as it is already pinned).
> >
> >As Ville has extracted the linear alignment, we can export that and all
> >pin_to_display directly so that we can set up the fbdev without the
> >confusion of calling intel_pin_and_fence_fb. Or we can just live with
> >the confustion and comment appropriately.
> 
> Ok, think I get it now. Will send three RFC patches shortly.
> 
> 1/3 looks innocent but it actually a bugfix once display address
> caching come along.
> 
> 2/3 is the caching itself.
> 
> 3/3 is what is not yet needed today, but analogous to 1/3 it fixes a
> bug which will become apparent in the future.
> 
> If this looks more along the lines of what you had in mind I can
> polish the comments or whatnot. 80 char line breaks were especially
> ugly in some of them to very long variable names. :)

Not far enough. It's not actually about caching the display address,
it's about tracking the actual VMA reference allocated for the plane.

What I had in mind and suggested yonks ago is:

http://cgit.freedesktop.org/~ickle/linux-2.6/commit/?h=nightly&id=2112f72b7adb94b0e038bbafe74a3c1ab6c851cf

Ignore the atomic interface changes, they are from a bygone era. The
important part is just in tracking vma and the
simplification/robustification that provides.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre