[PATCH 4.16 52/55] net: phy: sfp: fix the BR,min computation

Greg Kroah-Hartman
2018-05-18T08:15:48Z

From: Antoine Tenart <antoine.tenart@bootlin.com>

[ Upstream commit 52c5cd1bf0cecf4b146ca07dc513cbe2f4583bb5 ]

In an SFP EEPROM values can be read to get information about a given SFP
module. One of those is the bitrate, which can be determined using a
nominal bitrate in addition with min and max values (in %). The SFP code
currently compute both BR,min and BR,max values thanks to this nominal
and min,max values.

This patch fixes the BR,min computation as the min value should be
subtracted to the nominal one, not added.

Fixes: 9962acf7fb8c ("sfp: add support for 1000Base-PX and 1000Base-BX10")
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/phy/sfp-bus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/phy/sfp-bus.c
+++ b/drivers/net/phy/sfp-bus.c
@@ -190,7 +190,7 @@ void sfp_parse_support(struct sfp_bus *b
if (id->base.br_nominal) {
if (id->base.br_nominal != 255) {
br_nom = id->base.br_nominal * 100;
- br_min = br_nom + id->base.br_nominal * id->ext.br_min;
+ br_min = br_nom - id->base.br_nominal * id->ext.br_min;
br_max = br_nom + id->base.br_nominal * id->ext.br_max;
} else if (id->ext.br_max) {
br_nom = 250 * id->ext.br_max;