[Intel-gfx] [PATCH 11/11] drm/i915: Expand subslice mask

[Summers, Stuart]

On Wed, 2019-08-21 at 23:49 +0100, Chris Wilson wrote:
> Quoting Stuart Summers (2019-08-21 00:05:44)
> > Currently, the subslice_mask runtime parameter is stored as an
> > array of subslices per slice. Expand the subslice mask array to
> > better match what is presented to userspace through the
> > I915_QUERY_TOPOLOGY_INFO ioctl. The index into this array is
> > then calculated:
> >   slice * subslice stride + subslice index / 8
> > 
> > v2: Fix 32-bit build
> > v3: Use new helper function in SSEU workaround warning message
> > 
> > Signed-off-by: Stuart Summers <stuart.summers at intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_sseu.c        | 27
> > ++++++++++++++++++++-
> >  drivers/gpu/drm/i915/gt/intel_sseu.h        |  5 +++-
> >  drivers/gpu/drm/i915/gt/intel_workarounds.c |  5 ++--
> >  drivers/gpu/drm/i915/i915_debugfs.c         |  5 +++-
> >  drivers/gpu/drm/i915/intel_device_info.c    |  8 +++---
> >  5 files changed, 40 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_sseu.c
> > b/drivers/gpu/drm/i915/gt/intel_sseu.c
> > index 5d537ec97fcc..eae1c7b20688 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_sseu.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_sseu.c
> > @@ -30,6 +30,31 @@ intel_sseu_subslice_total(const struct
> > sseu_dev_info *sseu)
> >         return total;
> >  }
> >  
> > +u32 intel_sseu_get_subslices(const struct sseu_dev_info *sseu, u8
> > slice)
> > +{
> > +       int i, offset = slice * sseu->ss_stride;
> > +       u32 mask = 0;
> > +
> > +       if (slice >= sseu->max_slices) {
> > +               DRM_ERROR("%s: invalid slice %d, max: %d\n",
> > +                         __func__, slice, sseu->max_slices);
> > +               return 0;
> > +       }
> 
> That's a programmer error, we only need it during development. I am a
> proponent of making it explode as early as possible and make people
> fix
> it rather than ignore it.

I guess this was trigger shyness on my part after bringing some of the
ICL machines down with my first post of this series :) I agree this
seems like the right thing to do though. I'll make the change in the
next revision.

> 
> > +       if (sseu->ss_stride > sizeof(mask)) {
> > +               DRM_ERROR("%s: invalid subslice stride %d, max:
> > %u\n",
> > +                         __func__, sseu->ss_stride,
> > +                        (unsigned int)sizeof(mask));
> > +               return 0;
> > +       }
> 
> Put the assertion in the constructor (set_sseu_info or whatever it
> was
> called)

Makes sense.

> 
> > +
> > +       for (i = 0; i < sseu->ss_stride; i++)
> > +               mask |= (u32)sseu->subslice_mask[offset + i] <<
> > +                       i * BITS_PER_BYTE;
> 
> Otherwise, the actual conversions look fairly straightforward,
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

Thanks!

-Stuart

> -Chris
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