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

[Chris Wilson]

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.

> +       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)

> +
> +       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>
-Chris