[PATCH] ath10k: Prevent active scans on potential unusable channels

From: Sven Eckelmann <sven.eckelmann@openmesh.com>
To: ath10k@lists.infradead.org
Cc: Marek Puzyniak <marek.puzyniak@tieto.com>,
	Simon Wunderlich <simon.wunderlich@openmesh.com>,
	Sven Eckelmann <sven.eckelmann@openmesh.com>
Subject: [PATCH] ath10k: Prevent active scans on potential unusable channels
Date: Tue, 10 Jul 2018 11:44:48 +0200	[thread overview]
Message-ID: <20180710094448.13201-1-sven.eckelmann@openmesh.com> (raw)

The QCA4019 hw1.0 firmware 10.4-3.2.1-00050 and 10.4-3.5.3-00053 (and most
likely all other) seem to ignore the WMI_CHAN_FLAG_DFS flag during the
scan. This results in transmission (probe requests) on channels which are
not "available" for transmissions.

Since the firmware is closed source and nothing can be done from our side
to fix the problem in it, the driver has to work around this problem. The
WMI_CHAN_FLAG_PASSIVE seems to be interpreted by the firmware to not
scan actively on a channel unless an AP was detected on it. Simple probe
requests will then be transmitted by the STA on the channel.

ath10k must therefore also use this flag when it queues a radar channel for
scanning. This should reduce the chance of an active scan when the channel
might be "unusable" for transmissions.

Fixes: e8a50f8ba44b ("ath10k: introduce DFS implementation")
Signed-off-by: Sven Eckelmann <sven.eckelmann@openmesh.com>
---
Cc: Simon Wunderlich <simon.wunderlich@openmesh.com>
Cc: Marek Puzyniak <marek.puzyniak@tieto.com>
---
 drivers/net/wireless/ath/ath10k/mac.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 541bc1c4b2f7..ad975beae6dc 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -3085,6 +3085,13 @@ static int ath10k_update_channel_list(struct ath10k *ar)
 			passive = channel->flags & IEEE80211_CHAN_NO_IR;
 			ch->passive = passive;
 
+			/* the firmware is ignoring the "radar" flag of the
+			 * channel and is scanning actively using Probe Requests
+			 * on "Radar detection"/DFS channels which are not
+			 * marked as "available"
+			 */
+			ch->passive |= ch->chan_radar;
+
 			ch->freq = channel->center_freq;
 			ch->band_center_freq1 = channel->center_freq;
 			ch->min_power = 0;
-- 
2.11.0


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