Re: [PATCH 5/9] drm/i915: Add function to set subslices

[Chris Wilson <chris@chris-wilson.co.uk>]

Quoting Stuart Summers (2019-08-19 22:49:59)
> Add a new function to set a range of subslices for a
> specified slice based on a given mask.
> 
> v2: Use local variable for subslice_mask on HSW and
>     clean up a few other subslice_mask local variable
>     changes
> 
> Signed-off-by: Stuart Summers <stuart.summers@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_sseu.c     | 10 ++++
>  drivers/gpu/drm/i915/gt/intel_sseu.h     |  3 ++
>  drivers/gpu/drm/i915/intel_device_info.c | 59 +++++++++++++-----------
>  3 files changed, 46 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_sseu.c b/drivers/gpu/drm/i915/gt/intel_sseu.c
> index 3a5c0f7b5a08..f5ee43a034bd 100644
> --- a/drivers/gpu/drm/i915/gt/intel_sseu.c
> +++ b/drivers/gpu/drm/i915/gt/intel_sseu.c
> @@ -30,6 +30,16 @@ intel_sseu_subslice_total(const struct sseu_dev_info *sseu)
>         return total;
>  }
>  
> +void intel_sseu_set_subslices(struct sseu_dev_info *sseu, int slice,
> +                             u32 ss_mask)
> +{
> +       int i, offset = slice * sseu->ss_stride;
> +

Some sort of
	GEM_BUG_ON(sseu->ss_stride > 32);
to detect UB ?

> +       for (i = 0; i < sseu->ss_stride; i++)
> +               sseu->subslice_mask[offset + i] =
> +                       (ss_mask >> (BITS_PER_BYTE * i)) & 0xff;

This is a non-trivial transformation :|
-Chris
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