Comment 31 for bug 1016181

Ubuntu 12.04 kernel 3.2.0-29-generic with atheros wireless driver same issue:
it could stay connected for a long time but then all of a sudden the wireless drops.

chipset:
03:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev ff)

syslog extract:
ath: phy0: Unable to set channel
ath: phy0: Failed to stop TX DMA, queues=0x10f!
ath: phy0: DMA failed to stop in 10 ms AR_CR=0xffffffff AR_DIAG_SW=0xffffffff DMADBG_7=0xffffffff
ath: phy0: Could not stop RX, we could be confusing the DMA engine when we start RX up
ath: phy0: Chip reset failed
ath: phy0: Unable to reset channel, reset status -22

all the previous kernel releases since kernel 3.0 had the same issue as far as I can remember.
Installing compat-wireless didn' t resolve the problem