Re: [PATCH 2.6.39 v2] ath9k_hw: fix stopping rx DMA during resets

["John W. Linville" <linville@tuxdriver.com>]

On Fri, Apr 08, 2011 at 02:06:55PM +0200, Felix Fietkau wrote:
> During PHY errors, the MAC can sometimes fail to enter an idle state on older
> hardware (before AR9380) after an rx stop has been requested.
> 
> This typically shows up in the kernel log with messages like these:
> 
> ath: Could not stop RX, we could be confusing the DMA engine when we start RX up
> ------------[ cut here ]------------
> WARNING: at drivers/net/wireless/ath/ath9k/recv.c:504 ath_stoprecv+0xcc/0xf0 [ath9k]()
> Call Trace:
> [<8023f0e8>] dump_stack+0x8/0x34
> [<80075050>] warn_slowpath_common+0x78/0xa4
> [<80075094>] warn_slowpath_null+0x18/0x24
> [<80d66d60>] ath_stoprecv+0xcc/0xf0 [ath9k]
> [<80d642cc>] ath_set_channel+0xbc/0x270 [ath9k]
> [<80d65254>] ath_radio_disable+0x4a4/0x7fc [ath9k]
> 
> When this happens, the state that the MAC enters is easy to identify and
> does not result in bogus DMA traffic, however to ensure a working state
> after a channel change, the hardware should still be reset.
> 
> This patch adds detection for this specific MAC state, after which the above
> warnings completely disappear in my tests.
> 
> Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> Cc: stable@kernel.org
> Cc: Kyungwan Nam <Kyungwan.Nam@Atheros.com>
> 
> ---
> v2: remove a redundant ath9k_hw_stopdmarecv call, print the MAC DMA state when the error still occurs
> 
>  drivers/net/wireless/ath/ath9k/hw.c   |    9 ---------
>  drivers/net/wireless/ath/ath9k/mac.c  |   25 ++++++++++++++++++++++---
>  drivers/net/wireless/ath/ath9k/mac.h  |    2 +-
>  drivers/net/wireless/ath/ath9k/recv.c |    6 +++---
>  4 files changed, 26 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
> index 1b5bd13..c8a2d0d 100644
> --- a/drivers/net/wireless/ath/ath9k/hw.c
> +++ b/drivers/net/wireless/ath/ath9k/hw.c
> @@ -1249,15 +1249,6 @@ int ath9k_hw_reset(struct ath_hw *ah, struct ath9k_channel *chan,
>  	ah->txchainmask = common->tx_chainmask;
>  	ah->rxchainmask = common->rx_chainmask;
>  -	if ((common->bus_ops->ath_bus_type != ATH_USB) && !ah->chip_fullsleep) {

This patch seems a bit busted...?  I tried to fix it up manually but
the errors just keep coming...

-- 
John W. Linville		Someday the world will need a hero, and you
linville@tuxdriver.com			might be all we have.  Be ready.