[FS#863] ath9k failure with AP+11s VIFs ("unsupported hw bitrate detected")

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Matthias Schiffer (NeoRaider) 

Attached to Project - LEDE Project
Summary - ath9k failure with AP+11s VIFs ("unsupported hw bitrate detected")
Task Type - Bug Report
Category - Kernel
Status - Assigned
Assigned To - Felix Fietkau
Operating System - All
Severity - Medium
Priority - Medium
Reported Version - lede-17.01
Due in Version - Undecided
Due Date - Undecided
Details - A Gluon user reported the following issue, observed on a TL-WR841N v9 (QCA953x). LEDE version is 17.01.2.

Gluon uses AP+11s VIFs, with multicast_rate set to 12000.

The WLAN became unusable (no connection possible, WLAN LED permantently on) after a few hours of operation. Both VIFs were affected. The system recovered on its own after an hour in this state. Unfortunately, I have no information if beacons were still running in the broken state.

After the recovery, the large number of messages like the following were found in the kernel log:


[40085.953696] ath: phy0: unsupported hw bitrate detected 0x73 using 1 Mbit
[40200.844082] ath: phy0: unsupported hw bitrate detected 0x48 using 1 Mbit
[40281.298039] ------------[ cut here ]------------
[40281.303081] WARNING: CPU: 0 PID: 0 at compat-wireless-2017-01-31/net/mac80211/rx.c:4214 ieee80211_rx_napi+0x130/0x8b0 [mac80211]()
[40281.315230] Rate marked as an HT rate but passed status->rate_idx is not an MCS index [0-76]: 100 (0x64)
[40281.325023] Modules linked in: iptable_nat ath9k nf_nat_ipv4 nf_conntrack_ipv6 nf_conntrack_ipv4 ipt_REJECT ipt_MASQUERADE ebtable_nat ebtable_filter ebtable_broute ath9k_common xt_time xt_tcpudp xt_state xt_quota xt_pkttype xt_physdev xt_owner xt_nat xt_multiport xt_mark xt_mac xt_limit xt_conntrack xt_comment xt_addrtype xt_TCPMSS xt_REDIRECT xt_LOG xt_CT nf_reject_ipv4 nf_nat_redirect nf_nat_masquerade_ipv4 nf_nat nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_rtcache nf_conntrack mac80211 iptable_mangle iptable_filter ip_tables ebtables ebt_vlan ebt_stp ebt_snat ebt_redirect ebt_pkttype ebt_mark_m ebt_mark ebt_limit ebt_ip6 ebt_ip ebt_dnat ebt_arpreply ebt_arp ebt_among ebt_802_3 br_netfilter ath9k_hw ath em_nbyte em_cmp sch_pie em_meta sch_gred sch_teql act_ipt sch_prio em_text sch_codel sch_red sch_fq sch_sfq sch_dsmark act_skbedit act_mirred em_u32 cls_u32 cls_tcindex cls_flow cls_route cls_fw sch_htb sch_hfsc batman_adv libcrc32c cfg80211 compat ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables x_tables dummy veth tun act_police cls_basic sch_tbf sch_ingress gpio_button_hotplug crc16 crc32c_generic crypto_hash
[40281.433128] CPU: 0 PID: 0 Comm: swapper Tainted: G        W       4.4.71 #0
[40281.440330] Stack : 803e32a4 00000000 00000001 80440000 8042d1dc 8042ce63 803c48ac 00000000
[40281.440330]    804a378c 00000004 00000000 8180e918 00000000 800a7664 803c9fa8 80430000
[40281.440330]    00000003 00000004 803c83b4 81809d5c 00000000 800a55e0 00000002 00000000
[40281.440330]    8042bf70 801f5300 00000000 00000000 00000000 00000000 00000000 00000000
[40281.440330]    00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[40281.440330]    ...
[40281.477351] Call Trace:
[40281.479951] [] vprintk_default+0x24/0x30
[40281.484917] [] printk+0x2c/0x38
[40281.489077] [] serial8250_get_mctrl+0x30/0x54
[40281.494512] [] warn_slowpath_common+0xa0/0xd0
[40281.499949] [] dump_stack+0x14/0x28
[40281.504473] [] show_stack+0x50/0x84
[40281.509003] [] warn_slowpath_common+0xa0/0xd0
[40281.514543] [] ieee80211_rx_napi+0x130/0x8b0 [mac80211]
[40281.520918] [] warn_slowpath_fmt+0x2c/0x38
[40281.526158] [] ieee80211_rx_napi+0x130/0x8b0 [mac80211]
[40281.532495] [] __build_skb+0x48/0xc8
[40281.537148] [] __netdev_alloc_skb+0xd0/0x148
[40281.542477] [] handle_int+0x134/0x140
[40281.547181] [] ath9k_cmn_rx_skb_postprocess+0x50/0x168 [ath9k_common]
[40281.554852] [] ath_rx_tasklet+0xee8/0xf4c [ath9k]
[40281.560635] [] __bzero+0xa0/0x164
[40281.565012] [] ath_rx_tasklet+0xeb4/0xf4c [ath9k]
[40281.570828] [] ath9k_tasklet+0x200/0x28c [ath9k]
[40281.576512] [] tasklet_action+0x80/0xc8
[40281.581390] [] __do_softirq+0x250/0x298
[40281.586284] [] generic_handle_irq+0x24/0x3c
[40281.591540] [] plat_irq_dispatch+0xd4/0x10c
[40281.596760] [] handle_int+0x134/0x140
[40281.601447]
[40281.602992] ---[ end trace f41ea26ed5101c02 ]---


Both the numbers in the "unsupported hw bitrate detected" messages and the status->rate_idx values in the WARNINGs are seemingly random.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=863