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From 44c28420145101c846b445b8ae6159400909f69f Mon Sep 17 00:00:00 2001
From: Joshua Emele <jemele@acm.org>
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);
@@ -3717,7 +3722,12 @@ 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);
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