[PATCH] net/mlx5: fix Committed Bucket Size calculation

[Alexander Kozyrev]

Committed Bucket Size calculation tries to fit into 8-bit wide
mantissa field by setting 256 as a maximum value for it.
To compensate for this increase in the mantissa value the exponent
value has to be reduced by 8. But it gives a negative exponent
value for CBS less than 128. And negative exponent value is not
supported by the NIC. Adjust CSB calculation only for values
bigger than 128 to allow both small and big bucket sizes.

Fixes: 3bd26b23cef ("net/mlx5: support meter profile operations")
Cc: stable at dpdk.org

Signed-off-by: Alexander Kozyrev <akozyrev at nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
---
 drivers/net/mlx5/mlx5_flow_meter.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_flow_meter.c b/drivers/net/mlx5/mlx5_flow_meter.c
index 0dc7fbfb32..d0f8bcd100 100644
--- a/drivers/net/mlx5/mlx5_flow_meter.c
+++ b/drivers/net/mlx5/mlx5_flow_meter.c
@@ -295,8 +295,10 @@ mlx5_flow_meter_xbs_man_exp_calc(uint64_t xbs, uint8_t *man, uint8_t *exp)
 	}
 	/* xbs = xbs_mantissa * 2^xbs_exponent */
 	_man = frexp(xbs, &_exp);
-	_man = _man * pow(2, MLX5_MAN_WIDTH);
-	_exp = _exp - MLX5_MAN_WIDTH;
+	if (_exp >= MLX5_MAN_WIDTH) {
+		_man = _man * pow(2, MLX5_MAN_WIDTH);
+		_exp = _exp - MLX5_MAN_WIDTH;
+	}
 	*man = (uint8_t)ceil(_man);
 	*exp = _exp;
 }
-- 
2.18.2