From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleksij Rempel <linux@rempel-privat.de>
Date: Tue, 17 Dec 2013 19:26:32 +0100
Subject: [ath9k-devel] ath: phy0: unsupported hw bitrate detected 0x1b using
	1 Mbit
Message-ID: <52B09758.9070801@rempel-privat.de>
List-Id: <ath9k-devel.lists.ath9k.org>
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To: ath9k-devel@lists.ath9k.org

Hello all,

my kernel log spammed with this message:
ath: phy0: unsupported hw bitrate detected 0x1b using 1 Mbit

Hardware:
02:00.0 Network controller: Qualcomm Atheros AR9462 Wireless Network
Adapter (rev 01)
	Subsystem: Foxconn International, Inc. Device e052
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 64 bytes
	Interrupt: pin A routed to IRQ 17
	Region 0: Memory at f7c00000 (64-bit, non-prefetchable) [size=512K]
	Expansion ROM@f7c80000 [disabled] [size=64K]
	Capabilities: <access denied>
	Kernel driver in use: ath9k

According to the source it looks like a bug:
        /*
         * No valid hardware bitrate found -- we should not get here
         * because hardware has already validated this frame as OK.
         */
        ath_dbg(common, ANY,
                "unsupported hw bitrate detected 0x%02x using 1 Mbit\n",
                rx_stats->rs_rate);
        RX_STAT_INC(rx_rate_err);

-- 
Regards,
Oleksij