[ath9k-devel] DMA issues with ar9280 cards

[Luis R. Rodriguez <lrodriguez@atheros.com>]

On Wed, Feb 23, 2011 at 12:55:35AM -0800, Bernhard Schmidt wrote:
> Hi,
> 
> I have some issues using any of my AR9280 cards, identified as:
> - Ubiquiti SR71E
> [  172.321483] ieee80211 phy0: Atheros AR9280 Rev:2 mem=0xf9760000, irq=11
> - Sparklan WPEA-110N
> [   58.456404] ieee80211 phy0: Atheros AR9280 Rev:2 mem=0xf8760000, irq=11
> 
> On a recent wireless-testing kernel:
> # uname -a
> % Linux meshnode 2.6.38-rc6-wl-12466-g09f3227 #23 SMP Wed Feb 23 08:48:45 CET 2011 i686 GNU/Linux
> 
> I see this behaviour:
> # hostapd /etc/hostapd.conf
> % scan due to ht40 
> [  289.389379] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  289.397106] ath: Could not stop RX, we could be confusing the DMA engine when we start RX up
> [  289.548409] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  289.700270] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  289.707992] ath: Could not stop RX, we could be confusing the DMA engine when we start RX up
> [  289.728509] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  289.880228] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  289.887952] ath: Could not stop RX, we could be confusing the DMA engine when we start RX up
> [  289.908455] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  290.060168] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  290.067926] ath: Could not stop RX, we could be confusing the DMA engine when we start RX up
> ..

This should not be fatal but we do want to fix it, it was just hard to reproduce.
Can you paste your hostapd.conf ?

> % scan done, setting up the BSS
> [  296.060536] ath: Failed to stop TX DMA in 100 msec after killing last frame
> [  296.075985] ath: Failed to stop TX DMA in 100 msec after killing last frame
> [  296.083032] ath: Failed to stop TX DMA!
> [  296.099187] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  296.106884] ath: Could not stop RX, we could be confusing the DMA engine when we start RX up
> [  296.127247] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  297.163998] ath: Failed to stop TX DMA in 100 msec after killing last frame
> [  297.182977] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  297.190677] ath: Could not stop RX, we could be confusing the DMA engine when we start RX up
> [  297.211004] ath: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x42000020
> [  298.247659] ath: Failed to stop TX DMA in 100 msec after killing last frame
> % ..

If its so easy to reproduce we can likely fix this for good!

Do you see the same issue if you just have one card plugged in or
is this happening on two separate boxes?

  Luis