[PATCH net-next 2/9] lan78xx: disable U1/U2 power state transitions

[John Efstathiades]

Use macro DEFAULT_U1_U2_INIT_ENABLE to configure default behaviour
of U1/U2 link power state transitions (on/off).

Disable U1/U2 link power state transitions by default to reduce
URB processing latency and maximise throughput.

Signed-off-by: John Efstathiades <john.efstathia...@pebblebay.com>
---
 drivers/net/usb/lan78xx.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 1c872edc816a..38664b48329a 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -56,6 +56,8 @@
 #define TX_ALIGNMENT                   (4)
 #define RXW_PADDING                    2
 
+#define DEFAULT_U1_U2_INIT_ENABLE      false
+
 #define MIN_IPV4_DGRAM                 68
 
 #define LAN78XX_USB_VENDOR_ID          (0x0424)
@@ -1351,7 +1353,8 @@ static int lan78xx_link_reset(struct lan78xx_net *dev)
 
                phy_ethtool_ksettings_get(phydev, &ecmd);
 
-               if (dev->udev->speed == USB_SPEED_SUPER) {
+               if (DEFAULT_U1_U2_INIT_ENABLE &&
+                   dev->udev->speed == USB_SPEED_SUPER) {
                        if (ecmd.base.speed == 1000) {
                                /* disable U2 */
                                ret = lan78xx_read_reg(dev, USB_CFG1, &buf);
@@ -1368,6 +1371,11 @@ static int lan78xx_link_reset(struct lan78xx_net *dev)
                                buf |= USB_CFG1_DEV_U1_INIT_EN_;
                                ret = lan78xx_write_reg(dev, USB_CFG1, buf);
                        }
+               } else {
+                       ret = lan78xx_read_reg(dev, USB_CFG1, &buf);
+                       buf &= ~USB_CFG1_DEV_U2_INIT_EN_;
+                       buf &= ~USB_CFG1_DEV_U1_INIT_EN_;
+                       ret = lan78xx_write_reg(dev, USB_CFG1, buf);
                }
 
                ladv = phy_read(phydev, MII_ADVERTISE);
-- 
2.17.1