[dpdk-dev] [PATCH] net/mlx5: fix the EIR calculation

[Bing Zhao <bingz@nvidia.com>]

Before the yellow color policy was supported, the only supported
profile of metering is RFC2697 and EIR is not part of the profile.
When creating a meter with this profile, the EIR part was always
zero.

After the yellow color policy supported and RFC2698 & 4115 support
was introduced, EIR is relevant and should be calculated. Usually
the EIR could not be zero and the formula for calculating CIR
mantissa & exponent could be reused.

The EIR could be 0 and then only green and red colors will be
supported from the specification. Both the mantissa and exponent
parts should be set to 0. Currently, the formula wrongly sets
non-zero values for the EIR=0 case.

Setting the mantissa and the exponent parts to zeros when EIR is 0
will solve the issue.

Fixes: 33a7493c8df8 ("net/mlx5: support meter for trTCM profiles")

Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>
---
 drivers/net/mlx5/mlx5_flow_meter.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_flow_meter.c b/drivers/net/mlx5/mlx5_flow_meter.c
index 0f51710907..a24bd9c7ae 100644
--- a/drivers/net/mlx5/mlx5_flow_meter.c
+++ b/drivers/net/mlx5/mlx5_flow_meter.c
@@ -245,17 +245,23 @@ mlx5_flow_meter_profile_validate(struct rte_eth_dev *dev,
 static inline void
 mlx5_flow_meter_xir_man_exp_calc(int64_t xir, uint8_t *man, uint8_t *exp)
 {
-	int64_t _cir;
+	int64_t _xir;
 	int64_t delta = INT64_MAX;
 	uint8_t _man = 0;
 	uint8_t _exp = 0;
 	uint64_t m, e;
 
+	/* Special case xir == 0 ? both exp and matissa are 0. */
+	if (xir == 0) {
+		*man = 0;
+		*exp = 0;
+		return;
+	}
 	for (m = 0; m <= 0xFF; m++) { /* man width 8 bit */
 		for (e = 0; e <= 0x1F; e++) { /* exp width 5bit */
-			_cir = (1000000000ULL * m) >> e;
-			if (llabs(xir - _cir) <= delta) {
-				delta = llabs(xir - _cir);
+			_xir = (1000000000ULL * m) >> e;
+			if (llabs(xir - _xir) <= delta) {
+				delta = llabs(xir - _xir);
 				_man = m;
 				_exp = e;
 			}
-- 
2.27.0