[PATCH V2 net-next 3/7] net: hns3: fix shaper parameter algorithm

From: Huazhong Tan
Date: Tue Sep 10 2019 - 22:43:46 EST


From: Yonglong Liu <liuyonglong@xxxxxxxxxx>

Currently when hns3 driver configures the tm shaper to limit
bandwidth below 20Mbit using the parameters calculated by
hclge_shaper_para_calc(), the actual bandwidth limited by tm
hardware module is not accurate enough, for example, 1.28 Mbit
when the user is configuring 1 Mbit.

This patch adjusts the ir_calc to be closer to ir, and
always calculate the ir_b parameter when user is configuring
a small bandwidth. Also, removes an unnecessary parenthesis
when calculating denominator.

Fixes: 848440544b41 ("net: hns3: Add support of TX Scheduler & Shaper to HNS3 driver")
Signed-off-by: Yonglong Liu <liuyonglong@xxxxxxxxxx>
Signed-off-by: Huazhong Tan <tanhuazhong@xxxxxxxxxx>
---
drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c
index e829101..9f0e35f 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hclge_tm.c
@@ -81,16 +81,13 @@ static int hclge_shaper_para_calc(u32 ir, u8 shaper_level,
return 0;
} else if (ir_calc > ir) {
/* Increasing the denominator to select ir_s value */
- while (ir_calc > ir) {
+ while (ir_calc >= ir && ir) {
ir_s_calc++;
ir_calc = DIVISOR_IR_B_126 / (tick * (1 << ir_s_calc));
}

- if (ir_calc == ir)
- *ir_b = 126;
- else
- *ir_b = (ir * tick * (1 << ir_s_calc) +
- (DIVISOR_CLK >> 1)) / DIVISOR_CLK;
+ *ir_b = (ir * tick * (1 << ir_s_calc) + (DIVISOR_CLK >> 1)) /
+ DIVISOR_CLK;
} else {
/* Increasing the numerator to select ir_u value */
u32 numerator;
@@ -104,7 +101,7 @@ static int hclge_shaper_para_calc(u32 ir, u8 shaper_level,
if (ir_calc == ir) {
*ir_b = 126;
} else {
- u32 denominator = (DIVISOR_CLK * (1 << --ir_u_calc));
+ u32 denominator = DIVISOR_CLK * (1 << --ir_u_calc);
*ir_b = (ir * tick + (denominator >> 1)) / denominator;
}
}
--
2.7.4