drm/i915/pmu: Make PMU sample array two-dimensional

No functional changes but we can remove some unsightly index computation
and read/write functions if we convert the PMU sample array from a
one-dimensional to a two-dimensional array.

v2: Retain read/store helpers (Tvrtko)
Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230524215629.97920-3-ashutosh.dixit@intel.com

drivers/gpu/drm/i915/i915_pmu.c

@@ -191,31 +191,21 @@ static inline s64 ktime_since_raw(const ktime_t kt)
 	return ktime_to_ns(ktime_sub(ktime_get_raw(), kt));
 }
 
-static unsigned int
-__sample_idx(struct i915_pmu *pmu, unsigned int gt_id, int sample)
-{
-	unsigned int idx = gt_id * __I915_NUM_PMU_SAMPLERS + sample;
-
-	GEM_BUG_ON(idx >= ARRAY_SIZE(pmu->sample));
-
-	return idx;
-}
-
 static u64 read_sample(struct i915_pmu *pmu, unsigned int gt_id, int sample)
 {
-	return pmu->sample[__sample_idx(pmu, gt_id, sample)].cur;
+	return pmu->sample[gt_id][sample].cur;
 }
 
 static void
 store_sample(struct i915_pmu *pmu, unsigned int gt_id, int sample, u64 val)
 {
-	pmu->sample[__sample_idx(pmu, gt_id, sample)].cur = val;
+	pmu->sample[gt_id][sample].cur = val;
 }
 
 static void
 add_sample_mult(struct i915_pmu *pmu, unsigned int gt_id, int sample, u32 val, u32 mul)
 {
-	pmu->sample[__sample_idx(pmu, gt_id, sample)].cur += mul_u32_u32(val, mul);
+	pmu->sample[gt_id][sample].cur += mul_u32_u32(val, mul);
 }
 
 static u64 get_rc6(struct intel_gt *gt)

drivers/gpu/drm/i915/i915_pmu.h

@@ -127,7 +127,7 @@ struct i915_pmu {
 	 * Only global counters are held here, while the per-engine ones are in
 	 * struct intel_engine_cs.
 	 */
-	struct i915_pmu_sample sample[I915_PMU_MAX_GTS * __I915_NUM_PMU_SAMPLERS];
+	struct i915_pmu_sample sample[I915_PMU_MAX_GTS][__I915_NUM_PMU_SAMPLERS];
 	/**
 	 * @sleep_last: Last time GT parked for RC6 estimation.
 	 */