[Intel-gfx] [PATCH] drm/i915: Initialise subslice prior to potential zero-length loop

[Lionel Landwerlin]

On 29/05/2019 14:24, Chris Wilson wrote:
> Appease static analysers by making sure subslice always have a value.
>
> drivers/gpu/drm/i915//gt/intel_engine_cs.c:971 intel_sseu_fls_subslice() error: uninitialized symbol 'subslice'.
>
> There's also the nagging question of whether that fls() is off-by-one...
>
> Fixes: 1ac159e23c2c ("drm/i915: Expand subslice mask")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> Cc: Stuart Summers <stuart.summers at intel.com>
> Cc: Manasi Navare <manasi.d.navare at intel.com>


Stuart should probably rb this too as he's been looking after this 
topology stuff.

Looks good to me :


Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>


> ---
>   drivers/gpu/drm/i915/gt/intel_engine_cs.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index 158722b50691..fc880424be2f 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -956,12 +956,12 @@ const char *i915_cache_level_str(struct drm_i915_private *i915, int type)
>   static inline u32
>   intel_sseu_fls_subslice(const struct sseu_dev_info *sseu, u32 slice)
>   {
> -	u32 subslice;
> +	const u8 *subslice_mask = sseu->subslice_mask + slice * sseu->ss_stride;
> +	u32 subslice = 0;
>   	int i;
>   
>   	for (i = sseu->ss_stride - 1; i >= 0; i--) {
> -		subslice = fls(sseu->subslice_mask[slice * sseu->ss_stride +
> -						   i]);
> +		subslice = fls(subslice_mask[i]);
>   		if (subslice) {
>   			subslice += i * BITS_PER_BYTE;
>   			break;