[PATCH v5 3/3] wifi: mwifiex: add dt flag to ignore incorrect ROM regulatory hint

[Georgi Valkov <gvalkov@gmail.com>]

WRT3200ACM and WRT32x routers always report a fixed US regulatory domain
from the mwifiex ROM, which conflicts with the platform regulatory
configuration on units sold outside the US market. For example:
- phy0 mwlwifi 5 GHz, hard-coded region 98 EU mapped to FR
- phy1 mwlwifi 2.4 GHz, hard-coded region 98 EU mapped to FR
- phy2 mwifiex 2.4 and 5 GHz, hard-coded region US

When the system boots, it detects a conflict between the user selected
region and the radios, e.g. BG FR US, and applies extreme restrictions,
preventing use of 5 GHz and DFS channels. This also affects phy0.

Implement a device-tree flag, which allows affected platforms to ignore
an incorrect regulatory hint from ROM, so userspace can set the correct
platform regulatory domain. This avoids the region conflict and allows
the 5 GHz radios to be used.

The change affects only platforms which explicitly define this flag, and
helps overcome the incorrect behaviour of proprietary radio firmware.

[1] https://github.com/kaloz/mwlwifi/issues/173#issuecomment-307879699
[2] https://github.com/openwrt/openwrt/issues/9956

Tested-on WRT3200ACM, OpenWrt
iw reg get: no longer reports region for phy2

Cc: stable@vger.kernel.org
Signed-off-by: Georgi Valkov <gvalkov@gmail.com>
---
 drivers/net/wireless/marvell/mwifiex/cfg80211.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/wireless/marvell/mwifiex/cfg80211.c b/drivers/net/wireless/marvell/mwifiex/cfg80211.c
index abc703441c5d..26978158a0ad 100644
--- a/drivers/net/wireless/marvell/mwifiex/cfg80211.c
+++ b/drivers/net/wireless/marvell/mwifiex/cfg80211.c
@@ -4899,7 +4899,14 @@ int mwifiex_register_cfg80211(struct mwifiex_adapter *adapter)
 				country_code =
 					mwifiex_11d_code_2_region(
 						adapter->region_code);
+
+				/* Allow platforms to ignore an incorrect
+				 * regulatory hint from ROM, so userspace
+				 * can set the correct regulatory domain.
+				 */
 				if (country_code &&
+				    !device_property_read_bool(adapter->dev,
+							       "marvell,ignore-regulatory-hint") &&
 				    regulatory_hint(wiphy, country_code))
 					mwifiex_dbg(priv->adapter, ERROR,
 						    "regulatory_hint() failed\n");
-- 
2.55.0