Re: [PATCH v3 07/15] drm/i915: Add functions to allocate / release gem obj for GuC

Chris Wilson
2015-04-20T19:52:28Z

On Mon, Apr 20, 2015 at 09:02:20AM -0700, Yu Dai wrote:
>
>
> On 04/18/2015 06:47 AM, Chris Wilson wrote:
> >On Fri, Apr 17, 2015 at 02:21:12PM -0700, yu.dai@intel.com wrote:
> >> From: Alex Dai <yu.dai@intel.com>
> >>
> >> All gem objects used by GuC are pinned to ggtt space out of range
> >> [0, WOPCM size]. In GuC address space mapping, [0, WPOCM size] is
> >> used internally for its Boot ROM, SRAM etc. Currently this WPOCM
> >> size is 512K. This is done by using of PIN_OFFSET_BIAS.
> >
> >If the region is reserved, remove that region from the GGTT drm_mm range
> >manager. Then the restriction is applied to all objects and not in a
> >hodge-podge fashion like this.
> >
> I don't think I have clearly explained this. GTT range [0, WPOCM
> size] can't be used by GuC firmware, but still others can use it
> without any issue. PIN_OFFSET_BIAS is great for such use case.

You mean that the GuC redirects the [0, WOPCM] range to an internal set
of preallocated PTEs?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre