[PATCH wireless 1/2] wifi: rtw88: program the channel when the device is started

[Jeremy Fareau]

The chip is reset by power_off()/power_on(), but mac80211 only calls
ieee80211_ops::config() when its own channel state changes.  After a
stop/start cycle, such as

    ip link set <dev> down
    ip link set <dev> up

the channel is unchanged from mac80211's point of view, so the radio is
never reprogrammed.  The device then listens on whatever channel the
hardware came up on while iw reports the configured one, and receives
almost nothing.

Observed with an RTL8814AU (ALFA AWUS1900) in monitor mode on an
aarch64 host.  A 25 s capture on channel 6 after a down/up cycle yields
3 frames, and 431 frames as soon as any real channel change is
requested.  An RTL8812AU (Linksys WUSB6300) on the same host, the same
channel and the same second yields 2438 frames.

Program the channel in rtw_ops_start(), like rtw_ips_pwr_up() already
does when leaving IPS.

Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
Assisted-by: LLM
Signed-off-by: Jeremy Fareau <jeremy.fareau@xxxxxxxxx>
---
 drivers/net/wireless/realtek/rtw88/mac80211.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw88/mac80211.c b/drivers/net/wireless/realtek/rtw88/mac80211.c
index b01b98d24b0a..827f38390969 100644
--- a/drivers/net/wireless/realtek/rtw88/mac80211.c
+++ b/drivers/net/wireless/realtek/rtw88/mac80211.c
@@ -57,6 +57,17 @@ static int rtw_ops_start(struct ieee80211_hw *hw)
 
 	mutex_lock(&rtwdev->mutex);
 	ret = rtw_core_start(rtwdev);
+
+	/* The chip is reset by power_off()/power_on(), but mac80211 only calls
+	 * ieee80211_ops::config() when its own channel state changes. After a
+	 * stop/start cycle the channel is unchanged from mac80211's point of
+	 * view, so the radio would never be reprogrammed and the device would
+	 * receive nothing. Program it here, like rtw_ips_pwr_up() already does
+	 * when leaving IPS.
+	 */
+	if (!ret && hw->conf.chandef.chan)
+		rtw_set_channel(rtwdev);
+
 	mutex_unlock(&rtwdev->mutex);
 
 	return ret;
-- 
2.43.0