[Intel-gfx] [PATCH] drm/i915: Shift driver's HWSP usage out of reserved range

[Daniel Vetter]

On Tue, Feb 24, 2015 at 10:20:17AM +0000, Daniel, Thomas wrote:
> > -----Original Message-----
> > From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
> > Sent: Monday, February 23, 2015 11:28 PM
> > To: Gordon, David S
> > Cc: Daniel, Thomas; intel-gfx at lists.freedesktop.org
> > Subject: Re: [Intel-gfx] [PATCH] drm/i915: Shift driver's HWSP usage out of
> > reserved range
> > 
> > On Thu, Feb 19, 2015 at 02:58:48PM +0000, Dave Gordon wrote:
> > > On 18/02/15 11:48, Thomas Daniel wrote:
> > > > As of Gen6, the general purpose area of the hardware status page has shrunk
> > and
> > > > now begins at dword 0x30.  i915 driver uses dword 0x20 to store the seqno
> > which
> > > > is now reserved.  So shift our HWSP dwords up into the general purpose
> > range
> > > > before this bites us.
> > 
> > It would be really interesting to know what exactly the hw does with
> > offsets below 0x30 ... it might explain some of the bugs we've seen. Can
> > you please digg that out so that I can amend the commit message?
> 
> All documentation I've seen just says "Reserved" for current hardware
> including SKL so we can't rely on any particular usage.  That's why I
> just put "Reserved" for these dwords in the comment.

Thanks for the clarification, I've ammended the commit message.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch