[PATCH 2/2] wifi: ath11k: apply the initial regdomain before registering the wiphy

[Nikolay Bryskin <nbryskin@gmail.com>]

ath11k marks its wiphy REGULATORY_WIPHY_SELF_MANAGED in
ath11k_reg_init(), but applies the regdomain received from the firmware
only after ieee80211_register_hw(), and asynchronously:
regulatory_set_wiphy_regd() just stores the request and schedules
reg_work. Userspace is told about the new wiphy from wiphy_register(), so
it can query the regdomain before there is one. iwd does exactly that as
soon as the wiphy appears, which triggers the WARN_ON() in
nl80211_get_reg_do():

  !regdom && self_managed
  WARNING: net/wireless/nl80211.c:10576 at nl80211_get_reg_do+0x229/0x270 [cfg80211], CPU#4: iwd/716
  Call Trace:
   genl_family_rcv_msg_doit+0x144/0x1a0
   genl_rcv_msg+0x1cc/0x300
   netlink_rcv_skb+0xcd/0x150
   genl_rcv+0x28/0x40
   netlink_unicast+0x2fb/0x4a0
   netlink_sendmsg+0x219/0x480
   __sys_sendto+0x226/0x230
   ...

The regdomain is already known at that point (ab->default_regd[], or
ab->new_regd[] if an update arrived meanwhile), so apply it before
ieee80211_register_hw(). wiphy_register() then installs the pending
regdomain itself, via wiphy_regulatory_register() ->
reg_process_self_managed_hints(). That happens under the same RTNL hold
as the NL80211_CMD_NEW_WIPHY notification, and nl80211_get_reg_do() takes
the RTNL as well, so userspace can no longer see the wiphy without its
regdomain.

The window matters beyond the warning. With an msleep(2000) inserted
after ieee80211_register_hw() for testing, iwd associated before the
regdomain was applied; the late regdomain then went through
ath11k_reg_notifier() ("driver initiated regd update") and the channel
list update to the firmware while associated, and from then on TX was
badly degraded while RX stayed fine (QCA6390, 5 GHz DFS channel, signal
-33 dBm, no beacon loss):

  tx packets: 2012, tx failed: 1678, tx retries: 0
  tx bitrate: 48.0 MBit/s
  rx bitrate: 648.5 MBit/s 80MHz HE-MCS 6 HE-NSS 2

ping showed 39% loss. Without the delay, the WARN_ON() shows up at boot
only occasionally. With this patch and the same delay neither the
warning nor the TX degradation occurred.

Tested-on: QCA6390 hw2.0 PCI WLAN.HST.1.0.1-05266-QCAHSTSWPLZ_V2_TO_X86-1

Fixes: d5c65159f289 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Link: https://lore.kernel.org/all/16aa99921c4e92e8d4da3c84aacbec2e673666aa.camel@sipsolutions.net/
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Nikolay Bryskin <nbryskin@gmail.com>
---
 drivers/net/wireless/ath/ath11k/mac.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
index 3dfd24d7b5a6..4ebdde872213 100644
--- a/drivers/net/wireless/ath/ath11k/mac.c
+++ b/drivers/net/wireless/ath/ath11k/mac.c
@@ -10648,6 +10648,16 @@ static int __ath11k_mac_register(struct ath11k *ar)
 	    ab->hw_params.bios_sar_capa)
 		ar->hw->wiphy->sar_capa = ab->hw_params.bios_sar_capa;
 
+	/* Apply the regd received during initialization. Do it before
+	 * registering so that cfg80211 installs it while registering the
+	 * wiphy, before userspace can query a self-managed wiphy without one.
+	 */
+	ret = ath11k_regd_update(ar);
+	if (ret) {
+		ath11k_err(ar->ab, "ath11k regd update failed: %d\n", ret);
+		goto err_free_if_combs;
+	}
+
 	ret = ieee80211_register_hw(ar->hw);
 	if (ret) {
 		ath11k_err(ar->ab, "ieee80211 registration failed: %d\n", ret);
@@ -10662,13 +10672,6 @@ static int __ath11k_mac_register(struct ath11k *ar)
 		 */
 		ar->hw->wiphy->interface_modes &= ~BIT(NL80211_IFTYPE_MONITOR);
 
-	/* Apply the regd received during initialization */
-	ret = ath11k_regd_update(ar);
-	if (ret) {
-		ath11k_err(ar->ab, "ath11k regd update failed: %d\n", ret);
-		goto err_unregister_hw;
-	}
-
 	if (ab->hw_params.current_cc_support && ab->new_alpha2[0]) {
 		memcpy(&ar->alpha2, ab->new_alpha2, 2);
 		ret = ath11k_reg_set_cc(ar);
-- 
2.56.0