[PATCH] wifi: ath12k: Add fallback regulatory domain for WCN7850 without SMBIOS

[Saikiran <bjsaikiran@gmail.com>]

When SMBIOS doesn't provide country code data (common on some Lenovo
X Elite laptops), initialize with world domain (00) and skip sending
it to firmware to let firmware use its default regulatory settings.

Without this, new_alpha2 remains uninitialized and firmware receives
invalid country code, causing repeated regulatory update failures.

Note: This workaround doesn't fully resolve the regulatory failures
seen on WCN7850 hw2.0 with firmware WLAN.HMT.1.1.c5-00302. The firmware
still rejects regulatory settings during early initialization, keeping
the device in passive-scan-only mode for 5GHz channels. Further firmware
debugging is needed to resolve the root cause.

Link: https://bugs.launchpad.net/ubuntu-concept/+bug/2138308
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00302 (Lenovo Yoga Slim 7x)

Signed-off-by: Saikiran <bjsaikiran@gmail.com>
---
 drivers/net/wireless/ath/ath12k/core.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/net/wireless/ath/ath12k/core.c b/drivers/net/wireless/ath/ath12k/core.c
index cc352eef1939..4121dd14bbcc 100644
--- a/drivers/net/wireless/ath/ath12k/core.c
+++ b/drivers/net/wireless/ath/ath12k/core.c
@@ -800,6 +800,18 @@ int ath12k_core_check_smbios(struct ath12k_base *ab)
 	ab->qmi.target.bdf_ext[0] = '\0';
 	dmi_walk(ath12k_core_check_cc_code_bdfext, ab);
 
+	/* If SMBIOS doesn't provide country code, initialize with world domain (00)
+	 * to let firmware use its default regulatory settings
+	 */
+	spin_lock_bh(&ab->base_lock);
+	if (ab->new_alpha2[0] == 0 && ab->new_alpha2[1] == 0) {
+		/* Use world domain - let firmware decide */
+		ab->new_alpha2[0] = '0';
+		ab->new_alpha2[1] = '0';
+		ath12k_info(ab, "No SMBIOS country code, using world regulatory domain\n");
+	}
+	spin_unlock_bh(&ab->base_lock);
+
 	if (ab->qmi.target.bdf_ext[0] == '\0')
 		return -ENODATA;
 
@@ -1522,6 +1534,12 @@ static void ath12k_update_11d(struct work_struct *work)
 	memcpy(&arg.alpha2, &ab->new_alpha2, 2);
 	spin_unlock_bh(&ab->base_lock);
 
+	/* Skip setting country code if it's world domain (00) - let firmware use defaults */
+	if (arg.alpha2[0] == '0' && arg.alpha2[1] == '0') {
+		ath12k_dbg(ab, ATH12K_DBG_WMI, "skip sending world domain to firmware\n");
+		return;
+	}
+
 	ath12k_dbg(ab, ATH12K_DBG_WMI, "update 11d new cc %c%c\n",
 		   arg.alpha2[0], arg.alpha2[1]);
 
-- 
2.51.0