From 44c28420145101c846b445b8ae6159400909f69f Mon Sep 17 00:00:00 2001 From: Joshua Emele Date: Wed, 7 Nov 2018 16:07:40 -0800 Subject: [PATCH 454/454] lan78xx: Debounce link events to minimize poll storm The bInterval is set to 4 (i.e. 8 microframes => 1ms) and the only bit that the driver pays attention to is "link was reset". If there's a flapping status bit in that endpoint data, (such as if PHY negotiation needs a few tries to get a stable link) then polling at a slower rate would act as a de-bounce. See: https://github.com/raspberrypi/linux/issues/2447 --- drivers/net/usb/lan78xx.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/drivers/net/usb/lan78xx.c +++ b/drivers/net/usb/lan78xx.c @@ -425,6 +425,11 @@ static bool enable_tso; module_param(enable_tso, bool, 0644); MODULE_PARM_DESC(enable_tso, "Enables TCP segmentation offload"); +#define INT_URB_MICROFRAMES_PER_MS 8 +static int int_urb_interval_ms = 8; +module_param(int_urb_interval_ms, int, 0); +MODULE_PARM_DESC(int_urb_interval_ms, "Override usb interrupt urb interval"); + static int lan78xx_read_reg(struct lan78xx_net *dev, u32 index, u32 *data) { u32 *buf = kmalloc(sizeof(u32), GFP_KERNEL); @@ -3714,7 +3719,12 @@ static int lan78xx_probe(struct usb_inte dev->pipe_intr = usb_rcvintpipe(dev->udev, dev->ep_intr->desc.bEndpointAddress & USB_ENDPOINT_NUMBER_MASK); - period = dev->ep_intr->desc.bInterval; + if (int_urb_interval_ms <= 0) + period = dev->ep_intr->desc.bInterval; + else + period = int_urb_interval_ms * INT_URB_MICROFRAMES_PER_MS; + + netif_notice(dev, probe, netdev, "int urb period %d\n", period); maxp = usb_maxpacket(dev->udev, dev->pipe_intr, 0); buf = kmalloc(maxp, GFP_KERNEL);