smsc95xx: enable power saving mode during system suspend

This patch enables the device to enter its lowest power SUSPEND2
state during system suspend, instead of staying up using full power.

Patch updated to not add two pointers to .suspend & .resume.

Patch updated to replace BUG_ON with WARN_ON_ONCE and return.
Signed-off-by: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/smsc95xx.c

@@ -1018,6 +1018,32 @@ static void smsc95xx_unbind(struct usbnet *dev, struct usb_interface *intf)
 	}
 }
 
+static int smsc95xx_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	struct usbnet *dev = usb_get_intfdata(intf);
+	int ret;
+	u32 val;
+
+	if (WARN_ON_ONCE(!dev))
+		return -EINVAL;
+
+	ret = usbnet_suspend(intf, message);
+	check_warn_return(ret, "usbnet_suspend error");
+
+	netdev_info(dev->net, "entering SUSPEND2 mode");
+
+	ret = smsc95xx_read_reg(dev, PM_CTRL, &val);
+	check_warn_return(ret, "Error reading PM_CTRL");
+
+	val &= ~(PM_CTL_SUS_MODE_ | PM_CTL_WUPS_ | PM_CTL_PHY_RST_);
+	val |= PM_CTL_SUS_MODE_2;
+
+	ret = smsc95xx_write_reg(dev, PM_CTRL, val);
+	check_warn_return(ret, "Error writing PM_CTRL");
+
+	return 0;
+}
+
 static void smsc95xx_rx_csum_offload(struct sk_buff *skb)
 {
 	skb->csum = *(u16 *)(skb_tail_pointer(skb) - 2);
@@ -1280,7 +1306,7 @@ static struct usb_driver smsc95xx_driver = {
 	.name		= "smsc95xx",
 	.id_table	= products,
 	.probe		= usbnet_probe,
-	.suspend	= usbnet_suspend,
+	.suspend	= smsc95xx_suspend,
 	.resume		= usbnet_resume,
 	.reset_resume	= usbnet_resume,
 	.disconnect	= usbnet_disconnect,

drivers/net/usb/smsc95xx.h

@@ -84,12 +84,16 @@
 #define HW_CFG_BCE_			(0x00000002)
 #define HW_CFG_SRST_			(0x00000001)
 
+#define RX_FIFO_INF			(0x18)
+
 #define PM_CTRL				(0x20)
+#define PM_CTL_RES_CLR_WKP_STS		(0x00000200)
 #define PM_CTL_DEV_RDY_			(0x00000080)
 #define PM_CTL_SUS_MODE_		(0x00000060)
 #define PM_CTL_SUS_MODE_0		(0x00000000)
 #define PM_CTL_SUS_MODE_1		(0x00000020)
-#define PM_CTL_SUS_MODE_2		(0x00000060)
+#define PM_CTL_SUS_MODE_2		(0x00000040)
+#define PM_CTL_SUS_MODE_3		(0x00000060)
 #define PM_CTL_PHY_RST_			(0x00000010)
 #define PM_CTL_WOL_EN_			(0x00000008)
 #define PM_CTL_ED_EN_			(0x00000004)