On Wed, Dec 21, 2016 at 04:30:14PM +0100, Michal Wajdeczko wrote:
> On Wed, Dec 21, 2016 at 02:11:26PM +0000, Chris Wilson wrote:
> > The GuC would like to own the upper portion of the GTT for itself, so
> > exclude it from our drm_mm to prevent us using it.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
> > Cc: Arkadiusz Hiler <arkadiusz.hiler@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_gem_gtt.c | 5 +++++
> > drivers/gpu/drm/i915/intel_guc_fwif.h | 3 +++
> > 2 files changed, 8 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > index 6af9311f72f5..96bc0e83286a 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> > @@ -3176,6 +3176,11 @@ int i915_ggtt_probe_hw(struct drm_i915_private *dev_priv)
> > if (ret)
> > return ret;
> >
> > + if (HAS_GUC_SCHED(dev_priv)) {
>
> Btw, shouldn't we also modify HAS_GUC_SCHED macro to look at i915.enable_guc_submission
> instead of .has_guc ? Note that Guc may be present but disabled...
And we don't really know at this point, since i915.enable_guc_submission
is resolved later.
if (HAS_GUC_SCHED(dev_priv) && i915.enable_guc_submission) is
conservative enough.
> > + ggtt->base.total -= GUC_GGTT_RESERVED_TOP;
>
> Hmm, while unlikely, what if RESERVED_TOP is larger than detected base.total ?
Then we are screwed :)
- if (HAS_GUC_SCHED(dev_priv)) {
+ if (HAS_GUC_SCHED(dev_priv) && i915.enable_guc_submission) {
+ if (WARN(ggtt->base.total < GUC_GGTT_RESERVED_TOP,
+ "Only found %lldMiB, but need %dMiB for the GuC",
+ ggtt->base.total >> 20, GUC_GGTT_RESERVED_TOP >> 20))
+ return -ENODEV;
+
ggtt->base.total -= GUC_GGTT_RESERVED_TOP;
ggtt->mappable_end = min(ggtt->mappable_end, ggtt->base.total);
}
> > + ggtt->mappable_end = min(ggtt->mappable_end, ggtt->base.total);
> > + }
> > +
> > if ((ggtt->base.total - 1) >> 32) {
> > DRM_ERROR("We never expected a Global GTT with more than 32bits"
> > " of address space! Found %lldM!\n",
> > diff --git a/drivers/gpu/drm/i915/intel_guc_fwif.h b/drivers/gpu/drm/i915/intel_guc_fwif.h
> > index 3202b32b5638..3361d38ed859 100644
> > --- a/drivers/gpu/drm/i915/intel_guc_fwif.h
> > +++ b/drivers/gpu/drm/i915/intel_guc_fwif.h
> > @@ -23,6 +23,9 @@
> > #ifndef _INTEL_GUC_FWIF_H
> > #define _INTEL_GUC_FWIF_H
> >
> > +/* A small region at the top of the global GTT is reserved for use by the GuC */
> > +#define GUC_GGTT_RESERVED_TOP 0x1200000
>
> Is this region size fixed (part of Guc HW assumptions), or it can change per different FW?
> If former, then maybe this macro should be moved to i915_guc_reg.h?
> If latter, then maybe it is worth to explictly state that in the comment?
This is purely guess work. Feel free to supply the mising details...
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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