During mac80211 software scan, carl9170_set_channel() can return -EIO
if the firmware is busy (TX queue draining, AGC calibration timeout).
This error propagates back to mac80211 via carl9170_op_config(), which
then aborts the entire scan rather than advancing to the next channel.

Add sw_scan_start/sw_scan_complete callbacks to track the scanning
state in a new 'bool scanning' field in struct ar9170.  When a channel
change fails during an active scan, log the failure at wiphy_dbg level
and return 0 so mac80211 advances to the next scan channel instead of
aborting.  Channel-change failures outside of a scan continue to
propagate the error normally.

Signed-off-by: Masi Osmani <mas-i@hotmail.de>
---
 drivers/net/wireless/ath/carl9170/carl9170.h |  1 +
 drivers/net/wireless/ath/carl9170/main.c     | 35 +++++++++++++++++++
 2 files changed, 36 insertions(+)

--- a/drivers/net/wireless/ath/carl9170/carl9170.h
+++ b/drivers/net/wireless/ath/carl9170/carl9170.h
@@ -335,6 +335,7 @@
 	/* PHY */
 	struct ieee80211_channel *channel;
 	unsigned int num_channels;
+	bool scanning;
 	int noise[4];
 	unsigned int chan_fail;
 	unsigned int total_chan_fail;
--- a/drivers/net/wireless/ath/carl9170/main.c
+++ b/drivers/net/wireless/ath/carl9170/main.c
@@ -989,8 +989,16 @@

 		err = carl9170_set_channel(ar, hw->conf.chandef.chan,
 					   channel_type);
-		if (err)
+		if (err) {
+			if (ar->scanning) {
+				wiphy_dbg(ar->hw->wiphy,
+					  "scan: skip channel %d MHz, change failed (%d)\n",
+					  hw->conf.chandef.chan->center_freq,
+					  err);
+				err = 0;
+			}
 			goto out;
+		}

 		err = carl9170_update_survey(ar, false, true);
 		if (err)
@@ -1016,6 +1024,27 @@
 	return err;
 }

+static void carl9170_op_sw_scan_start(struct ieee80211_hw *hw,
+				      struct ieee80211_vif *vif,
+				      const u8 *mac_addr)
+{
+	struct ar9170 *ar = hw->priv;
+
+	mutex_lock(&ar->mutex);
+	ar->scanning = true;
+	mutex_unlock(&ar->mutex);
+}
+
+static void carl9170_op_sw_scan_complete(struct ieee80211_hw *hw,
+					 struct ieee80211_vif *vif)
+{
+	struct ar9170 *ar = hw->priv;
+
+	mutex_lock(&ar->mutex);
+	ar->scanning = false;
+	mutex_unlock(&ar->mutex);
+}
+
 static u64 carl9170_op_prepare_multicast(struct ieee80211_hw *hw,
 					 struct netdev_hw_addr_list *mc_list)
 {
@@ -1836,6 +1865,8 @@
 	.add_interface		= carl9170_op_add_interface,
 	.remove_interface	= carl9170_op_remove_interface,
 	.config			= carl9170_op_config,
+	.sw_scan_start		= carl9170_op_sw_scan_start,
+	.sw_scan_complete	= carl9170_op_sw_scan_complete,
 	.prepare_multicast	= carl9170_op_prepare_multicast,
 	.configure_filter	= carl9170_op_configure_filter,
 	.conf_tx		= carl9170_op_conf_tx,

--
Regards,
Masi Osmani