[PATCH next] crypto: qat - replace avg_array() with a better function

[david.laight.linux@gmail.com]

From: David Laight <david.laight.linux@gmail.com>

avg_array() is defined as a 'type independant' #define.
However the algorithm is only valid for unsigned types and the
implementation is only valid for u64.
All the callers pass temporary kmalloc() allocated arrays of u64.

Replace with a function that takes a pointer to a u64 array.

Change the implementation to sum the low and high 32bits of each
value separately and then compute the average.
This will be massively faster as it does two divisions rather than
one for each element.

Also removes some very pointless __unqual_scalar_typeof().
They could be 'auto _x = 0 ? x + 0 : 0;' even if the types weren't fixed.

Only compile tested.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
 .../intel/qat/qat_common/adf_tl_debugfs.c     | 38 ++++++++-----------
 1 file changed, 15 insertions(+), 23 deletions(-)

diff --git a/drivers/crypto/intel/qat/qat_common/adf_tl_debugfs.c b/drivers/crypto/intel/qat/qat_common/adf_tl_debugfs.c
index b81f70576683..a084437a2631 100644
--- a/drivers/crypto/intel/qat/qat_common/adf_tl_debugfs.c
+++ b/drivers/crypto/intel/qat/qat_common/adf_tl_debugfs.c
@@ -77,32 +77,24 @@ static int tl_collect_values_u64(struct adf_telemetry *telemetry,
  * @len: Number of elements.
  *
  * This algorithm computes average of an array without running into overflow.
+ * (Provided len is less than 2 << 31.)
  *
  * Return: average of values.
  */
-#define avg_array(array, len) (				\
-{							\
-	typeof(&(array)[0]) _array = (array);		\
-	__unqual_scalar_typeof(_array[0]) _x = 0;	\
-	__unqual_scalar_typeof(_array[0]) _y = 0;	\
-	__unqual_scalar_typeof(_array[0]) _a, _b;	\
-	typeof(len) _len = (len);			\
-	size_t _i;					\
-							\
-	for (_i = 0; _i < _len; _i++) {			\
-		_a = _array[_i];			\
-		_b = do_div(_a, _len);			\
-		_x += _a;				\
-		if (_y >= _len - _b) {			\
-			_x++;				\
-			_y -= _len - _b;		\
-		} else {				\
-			_y += _b;			\
-		}					\
-	}						\
-	do_div(_y, _len);				\
-	(_x + _y);					\
-})
+static u64 avg_array(const u64 *array, size_t len)
+{
+	u64 sum_hi = 0, sum_lo = 0;
+	size_t i;
+
+	for (i = 0; i < len; i++) {
+		sum_hi += array[i] >> 32;
+		sum_lo += (u32)array[i];
+	}
+
+	sum_lo += (u64)do_div(sum_hi, len) << 32;
+
+	return (sum_hi << 32) + div_u64(sum_lo, len);
+}
 
 /* Calculation function for simple counter. */
 static int tl_calc_count(struct adf_telemetry *telemetry,
-- 
2.39.5