rockchip: distribute net interrupts

This adds a hotplug script for distributing interrupts of eth0 and eth1
across different cores. Otherwise the forwarding performance between
eth0 and eth1 is severely affected.

The existing SMP distribution mechanic in OpenWrt can't be used here, as
the actual device IRQ has to be moved to dedicated cores. In case of
eth1, this is in fact the USB3 controller.

Signed-off-by: David Bauer <mail@david-bauer.net>

target/linux/rockchip/armv8/base-files/etc/hotplug.d/net/40-net-smp-affinity

@@ -0,0 +1,30 @@
+#!/bin/sh
+
+[ "$ACTION" = add ] || exit
+
+get_device_irq() {
+	local device="$1"
+
+	local line=$(grep -m 1 "${device}\$" /proc/interrupts)
+	echo $(echo ${line} | sed 's/:.*//')
+}
+
+set_interface_core() {
+	local core_mask="$1"
+	local interface="$2"
+	local device="$3"
+
+	[ -z "${device}" ] && device="$interface"
+
+	local irq=$(get_device_irq "$device")
+
+	echo "${core_mask}" > /proc/irq/${irq}/smp_affinity
+}
+
+case "$(board_name)" in
+friendlyarm,nanopi-r2s)
+	set_interface_core 2 "eth0"
+	set_interface_core 4 "eth1" "xhci-hcd:usb3"
+	;;
+esac
+