carl9170: monitor mode hangs due to channel changes

carl9170: monitor mode hangs due to channel changes

[Marco Fonseca]

Hello,

I'm seeing a problem with the carl driver.  If I change channels
repeatedly on the 2.4ghz band, monitoring (e.g. tcpdump) will
eventually halt.  I've seen this on various versions of the carl
driver/firmware (both from 1.9.4 to 1.9.7)

After monitoring has hung, changing to a 5ghz channel, causes
monitoring to resume.  Bouncing the interface (ip link set mon0
down/up) also fixes it.


Here are some steps to reproduce:

    # setup interface
    iw wlan0 interface add mon0 type monitor
    ip link set mon0 up


    # start channging channels
    while true ; do for i in 1 6 11 ; do iw mon0 set channel $i ; \
    sleep .250 ; done ; done


In a second terminal:
    tcpdump -i mon0


Wait until tcpdump stops printing.  I've seen the failure rate vary
greatly, sometime minutes, sometime hours, but usually less then an
hour.

Regards,

Marco Fonseca

Re: carl9170: monitor mode hangs due to channel changes

[Christian Lamparter]

Hello,

On Wednesday, March 20, 2013 09:50:13 PM Marco Fonseca wrote:
> I'm seeing a problem with the carl driver. If I change channels
> repeatedly on the 2.4ghz band, monitoring (e.g. tcpdump) will
> eventually halt.  I've seen this on various versions of the carl
> driver/firmware (both from 1.9.4 to 1.9.7)
thanks for reporting this. You could try either of the attached
patch and test if it alleviate the issue. If the patches do help
then the problem is caused by rf/phy (code) [which is a problem
since the rf/phy parts are taken from the vendor driver as we
have no docs or specs for it].

Regards,
	Chr
--

Patch 1: just reinitialize AGC_CONTROL
(can also be moved behind CMD_FREQ_START)
---
diff --git a/drivers/net/wireless/ath/carl9170/phy.c b/drivers/net/wireless/ath/carl9170/phy.c
index b72c09c..7fffee6 100644
--- a/drivers/net/wireless/ath/carl9170/phy.c
+++ b/drivers/net/wireless/ath/carl9170/phy.c
@@ -1638,6 +1638,13 @@ int carl9170_set_channel(struct ar9170 *ar, struct ieee80211_channel *channel,
 		cmd = CARL9170_CMD_FREQUENCY;
 	}
 
+	err = carl9170_write_reg(ar, AR9170_PHY_REG_AGC_CONTROL,
+		carl9170_def_val(AR9170_PHY_REG_AGC_CONTROL,
+				 channel->band == IEEE80211_BAND_2GHZ,
+				 conf_is_ht40(&ar->hw->conf)));
+	if (err)
+		return err;
+
 	err = carl9170_exec_cmd(ar, CARL9170_CMD_FREQ_START, 0, NULL, 0, NULL);
 	if (err)
 		return err;
---


Patch 2: always do warm reset when changing channels
---
diff --git a/drivers/net/wireless/ath/carl9170/phy.c b/drivers/net/wireless/ath/carl9170/phy.c
index b72c09c..643cc57 100644
--- a/drivers/net/wireless/ath/carl9170/phy.c
+++ b/drivers/net/wireless/ath/carl9170/phy.c
@@ -1578,7 +1578,7 @@ int carl9170_set_channel(struct ar9170 *ar, struct ieee80211_channel *channel,
 	u32 cmd, tmp, offs = 0, new_ht = 0;
 	int err;
 	enum carl9170_bw bw;
-	bool warm_reset;
+	bool warm_reset = true;
 	struct ieee80211_channel *old_channel = NULL;
 
 	bw = nl80211_to_carl(_bw);
@@ -1592,14 +1592,7 @@ int carl9170_set_channel(struct ar9170 *ar, struct ieee80211_channel *channel,
 	/* may be NULL at first setup */
 	if (ar->channel) {
 		old_channel = ar->channel;
-		warm_reset = (old_channel->band != channel->band) ||
-			     (old_channel->center_freq ==
-			      channel->center_freq) ||
-			     (ar->ht_settings != new_ht);
-
 		ar->channel = NULL;
-	} else {
-		warm_reset = true;
 	}
 
 	/* HW workaround */
---

Re: carl9170: monitor mode hangs due to channel changes

[Marco Fonseca]

As far as I can tell those patches fixed it.  I wasn't paying
attention and applied both patches though.  My environment
is a little different today and I will test some more on Monday.

If you think it would help, I can test the patches individually.

Thanks!

Marco

On Wed, Mar 20, 2013 at 11:09:47PM +0100, Christian Lamparter wrote:
> Hello,
> 
> On Wednesday, March 20, 2013 09:50:13 PM Marco Fonseca wrote:
> > I'm seeing a problem with the carl driver. If I change channels
> > repeatedly on the 2.4ghz band, monitoring (e.g. tcpdump) will
> > eventually halt.  I've seen this on various versions of the carl
> > driver/firmware (both from 1.9.4 to 1.9.7)
> thanks for reporting this. You could try either of the attached
> patch and test if it alleviate the issue. If the patches do help
> then the problem is caused by rf/phy (code) [which is a problem
> since the rf/phy parts are taken from the vendor driver as we
> have no docs or specs for it].
> 
> Regards,
> 	Chr

Re: carl9170: monitor mode hangs due to channel changes

[Christian Lamparter]

On Saturday 23 March 2013 21:00:38 you wrote:
> As far as I can tell those patches fixed it.  I wasn't paying
> attention and applied both patches though.  My environment is
> a little different today and I will test some more on Monday.
No worries. I can wait for the test results on Monday.
 
> If you think it would help, I can test the patches individually.
Yes. The second patch disables the "fast channel change" feature.
And this should be avoided, unless of course it is absolutely
necessary.

Regards,
	Chr