[Intel-gfx] [PATCH] drm/i915/bdw: Don't allow the FBC base to be 0

[Ben Widawsky]

On Fri, May 02, 2014 at 09:35:20PM +0100, Chris Wilson wrote:
> On Fri, May 02, 2014 at 10:00:01AM -0700, Ben Widawsky wrote:
> > On Fri, May 02, 2014 at 04:00:25PM +0300, Ville Syrjälä wrote:
> > > On Fri, May 02, 2014 at 09:38:11AM +0100, Chris Wilson wrote:
> > > > On Fri, May 02, 2014 at 11:19:27AM +0300, Ville Syrjälä wrote:
> > > > > On Thu, May 01, 2014 at 06:47:54PM -0700, Ben Widawsky wrote:
> > > > > > "Restriction :
> > > > > > The offset must be greater than 4K bytes, avoiding the first 4KB of
> > > > > > stolen memory."
> > > > > 
> > > > > Isn't this a more generic issue that we must avoid the first 4k? If so
> > > > > I think we should just reserve the first 4k permanently at driver init
> > > > > time.
> > 
> > Is anyone opposed to this plan? Realistically it won't make a
> > difference.
> > 
> > > > 
> > > > What? On many machines the vga framebuffer is allocated from offset 0. I
> > > > think some explanation is in order.
> > 
> > The chopped off part of the commit message explained it (if I understood
> > your point).
> 
> How do we handle the inherited fb if it starts at offset 0?
> -Chris
> 

I must be missing something important. The FBC buffer is the only one
requiring a non-zero offset from the base of stolen memory.

-- 
Ben Widawsky, Intel Open Source Technology Center