[PATCH v7 3/3] ARM: dts: armada: WRT3200ACM: add marvell,invalid-reg-hint-in-rom

[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 phy0 from starting on any DFS channel. phy2 works.

Add node wifi@1 with a flag marvell,invalid-reg-hint-in-rom to the
WRT3200ACM device-tree, which signals mwifiex that its regulatory
hint from ROM conflicts with the platform and should be ignored, so the
platform regulatory domain can be used. This does not allow the user to
change the regulatory config of any radio. It only allows phy0 to start
and operate according to its certified configuration. All radios in
WRT3200ACM/WRT32x are locked to the hard-coded configuration for which
they are certified.

On WRT3200ACM, the platform configuration is stored on the devinfo mtd3
partition, which is read-only: cert_region=EU modelNumber=WRT3200ACM-EU

The Linux kernel sources do not have support for WRT32x. An equivalent
patch for these routers has to be sent to OpenWrt.

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

Cc: stable@vger.kernel.org
Signed-off-by: Georgi Valkov <gvalkov@gmail.com>
---
 arch/arm/boot/dts/marvell/armada-385-linksys-rango.dts | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm/boot/dts/marvell/armada-385-linksys-rango.dts b/arch/arm/boot/dts/marvell/armada-385-linksys-rango.dts
index 4ab45f294de2..2bf29981a031 100644
--- a/arch/arm/boot/dts/marvell/armada-385-linksys-rango.dts
+++ b/arch/arm/boot/dts/marvell/armada-385-linksys-rango.dts
@@ -165,6 +165,15 @@ &sdhci {
 	wp-inverted;
 	bus-width = <8>;
 	status = "okay";
+
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	wifi@1 {
+		compatible = "marvell,sd8897";
+		reg = <1>;
+		marvell,invalid-reg-hint-in-rom;
+	};
 };
 
 &usb3_1_vbus {
-- 
2.55.0