On Wed, Dec 21, 2016 at 04:03:30PM +0000, Chris Wilson wrote:
> 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) {
Assuming that in the future HAS_GUC_SCHED will be corrected to take use sanitized
value of .enable_guc_submission, to avoid any mislead, I would rather go with
- if (HAS_GUC_SCHED(dev_priv) && i915.enable_guc_submission) {
+ if (HAS_GUC(dev_priv) && i915.enable_guc_submission) {
> + if (WARN(ggtt->base.total < GUC_GGTT_RESERVED_TOP,
> + "Only found %lldMiB, but need %dMiB for the GuC",
Please update message with "GGTT" or similar to capture context what is missing ;)
> + 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...
If only I knew ;) maybe another day.
With the proposed changes,
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
Thanks,
Michal
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