1. 下载openwrt最新代码
2. 下载openwrt官方的7621e驱动https://
github.com/openwrt/mtk-wifi-gpl3. 参考https://
code.google.com/p/openwrt-hiwifi/, 打上hc5761的补丁，使用其hc5761的config，并开启mtk-wifi-gpl
4. 编译完成通过ttl，sysupgrade -F -n openwrt-ramips-mt7620a-hiwifi-hc5761-squashfs-sysupgrade.bin刷机
5. 完成重启，2.4G能够开启
dmesg的输出：
[ 21.160000] ip_tables: (C) 2000-2006 Netfilter Core Team
[ 21.190000] xt_time: kernel timezone is -0000
[ 21.190000] cfg80211: Calling CRDA to update world regulatory domain
[ 21.190000] cfg80211: World regulatory domain updated:
[ 21.190000] cfg80211: DFS Master region: unset
[ 21.190000] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp), (dfs_cac_time)
[ 21.190000] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
[ 21.190000] cfg80211: (2457000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
[ 21.190000] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (N/A, 2000 mBm), (N/A)
[ 21.190000] cfg80211: (5170000 KHz - 5250000 KHz @ 160000 KHz), (N/A, 2000 mBm), (N/A)
[ 21.190000] cfg80211: (5250000 KHz - 5330000 KHz @ 160000 KHz), (N/A, 2000 mBm), (0 s)
[ 21.190000] cfg80211: (5490000 KHz - 5730000 KHz @ 160000 KHz), (N/A, 2000 mBm), (0 s)
[ 21.190000] cfg80211: (5735000 KHz - 5835000 KHz @ 80000 KHz), (N/A, 2000 mBm), (N/A)
[ 21.190000] cfg80211: (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 0 mBm), (N/A)
[ 21.190000] PPP generic driver version 2.4.2
[ 21.190000] PPP MPPE Compression module registered
[ 21.190000] NET: Registered protocol family 24
[ 21.530000] l2tp_ppp: PPPoL2TP kernel driver, V2.0
[ 21.560000] ieee80211 phy0: rt2x00_set_rt: Info - RT chipset 5390, rev 0500 detected
[ 21.570000] ieee80211 phy0: rt2x00_set_rf: Info - RF chipset 7620 detected
[ 21.580000] ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'
[ 29.030000] device eth0.1 entered promiscuous mode
[ 29.050000] device eth0 entered promiscuous mode
[ 29.380000] br-lan: port 1(eth0.1) entered forwarding state
[ 29.380000] br-lan: port 1(eth0.1) entered forwarding state
[ 31.380000] br-lan: port 1(eth0.1) entered forwarding state
[ 32.800000] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[ 32.800000] device wlan0 entered promiscuous mode
[ 32.800000] br-lan: port 2(wlan0) entered forwarding state
[ 32.820000] br-lan: port 2(wlan0) entered forwarding state
[ 32.820000] br-lan: port 2(wlan0) entered disabled state
[ 33.310000] br-lan: port 2(wlan0) entered forwarding state
[ 33.310000] br-lan: port 2(wlan0) entered forwarding state
[ 33.320000] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 35.310000] br-lan: port 2(wlan0) entered forwarding state
[ 202.070000] nf_conntrack: automatic helper assignment is deprecated and it will be removed soon. Use the iptables CT target to attach helpers instead.
[ 341.460000] br-lan: port 2(wlan0) entered disabled state
[ 341.460000] br-lan: port 1(eth0.1) entered disabled state
[ 341.470000] device eth0.1 left promiscuous mode
[ 341.480000] device eth0 left promiscuous mode
[ 341.480000] br-lan: port 1(eth0.1) entered disabled state
[ 341.510000] IPv6: ADDRCONF(NETDEV_UP): eth0.1: link is not ready
[ 341.540000] device wlan0 left promiscuous mode
[ 341.540000] br-lan: port 2(wlan0) entered disabled state
[ 341.580000] device eth0.1 entered promiscuous mode
[ 341.580000] device eth0 entered promiscuous mode
[ 341.590000] device wlan0 entered promiscuous mode
[ 341.600000] br-lan: port 2(wlan0) entered forwarding state
[ 341.600000] br-lan: port 2(wlan0) entered forwarding state
[ 341.600000] br-lan: port 1(eth0.1) entered forwarding state
[ 341.620000] br-lan: port 1(eth0.1) entered forwarding state
[ 343.600000] br-lan: port 2(wlan0) entered forwarding state
[ 343.620000] br-lan: port 1(eth0.1) entered forwarding state
[ 450.680000] ralink_soc_eth 10100000.ethernet eth0: port 0 link down
[ 450.700000] br-lan: port 1(eth0.1) entered disabled state
[ 455.570000] ralink_soc_eth 10100000.ethernet eth0: port 0 link up (100Mbps/Full duplex)
[ 455.590000] br-lan: port 1(eth0.1) entered forwarding state
[ 455.590000] br-lan: port 1(eth0.1) entered forwarding state
[ 456.340000] ralink_soc_eth 10100000.ethernet eth0: port 0 link down
[ 456.670000] br-lan: port 1(eth0.1) entered disabled state
[ 467.680000] ralink_soc_eth 10100000.ethernet eth0: port 1 link up (100Mbps/Full duplex)
[ 467.700000] br-lan: port 1(eth0.1) entered forwarding state
[ 467.700000] br-lan: port 1(eth0.1) entered forwarding state
[ 469.770000] br-lan: port 1(eth0.1) entered forwarding state
[ 689.200000] device wlan0 left promiscuous mode
[ 689.200000] br-lan: port 2(wlan0) entered disabled state
[ 690.960000] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[ 690.960000] device wlan0 entered promiscuous mode
[ 690.960000] br-lan: port 2(wlan0) entered forwarding state
[ 690.960000] br-lan: port 2(wlan0) entered forwarding state
[ 690.960000] br-lan: port 2(wlan0) entered disabled state
[ 691.290000] br-lan: port 2(wlan0) entered forwarding state
[ 691.290000] br-lan: port 2(wlan0) entered forwarding state
[ 691.290000] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 693.290000] br-lan: port 2(wlan0) entered forwarding state
[ 694.490000] ralink_soc_eth 10100000.ethernet eth0: port 1 link down
[ 694.500000] br-lan: port 1(eth0.1) entered disabled state
[ 706.690000] ralink_soc_eth 10100000.ethernet eth0: port 0 link up (100Mbps/Full duplex)
[ 706.690000] br-lan: port 1(eth0.1) entered forwarding state
[ 706.690000] br-lan: port 1(eth0.1) entered forwarding state
[ 708.690000] br-lan: port 1(eth0.1) entered forwarding state
ifconfig输出：
br-lan Link encap:Ethernet HWaddr 00:0C:43:76:20:C0
inet addr:192.168.2.1 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::20c:43ff:fe76:20c0/64 Scope:Link
inet6 addr: fdd0:afde:ef81::1/60 Scope:Global
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:22755 errors:0 dropped:0 overruns:0 frame:0
TX packets:20078 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2210682 (2.1 MiB) TX bytes:25968013 (24.7 MiB)
eth0 Link encap:Ethernet HWaddr 00:0C:43:76:20:C0
inet6 addr: fe80::20c:43ff:fe76:20c0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:25451 errors:0 dropped:36 overruns:0 frame:0
TX packets:22782 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:25377192 (24.2 MiB) TX bytes:2979554 (2.8 MiB)
Interrupt:5
eth0.1 Link encap:Ethernet HWaddr 00:0C:43:76:20:C0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1599 errors:0 dropped:0 overruns:0 frame:0
TX packets:1395 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:181428 (177.1 KiB) TX bytes:569380 (556.0 KiB)
eth0.2 Link encap:Ethernet HWaddr 00:0C:43:76:20:C0
inet addr:192.168.1.3 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::20c:43ff:fe76:20c0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:20079 errors:0 dropped:1752 overruns:0 frame:0
TX packets:20261 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:24521127 (23.3 MiB) TX bytes:2186590 (2.0 MiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:2927 errors:0 dropped:0 overruns:0 frame:0
TX packets:2927 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:212201 (207.2 KiB) TX bytes:212201 (207.2 KiB)
wlan0 Link encap:Ethernet HWaddr 00:0C:43:76:20:C0
inet6 addr: fe80::20c:43ff:fe76:20c0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:21169 errors:0 dropped:0 overruns:0 frame:0
TX packets:21692 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2353612 (2.2 MiB) TX bytes:26046717 (24.8 MiB)
从log看，5G已经识别了。