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

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Message-Id: <20210204113121.29786-3-john.efstathiades@pebblebay.com>
Date:   Thu,  4 Feb 2021 11:31:14 +0000
From:   John Efstathiades <john.efstathiades@...blebay.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     UNGLinuxDriver@...rochip.com, davem@...emloft.net,
        netdev@...r.kernel.org, john.efstathiades@...blebay.com
Subject: [PATCH net-next 2/9] lan78xx: disable U1/U2 power state transitions

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.efstathiades@...blebay.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