[PATCH] mac80211: rt2x00: fix MT7620 low RSSI issue

[Shiji Yang]

From: Shiji Yang <yangshiji66 at qq.com>

Introducing SoC specific RSSI base value to fix the low RSSI issue
on MT7620. With this fix[1], the RSSI value reported by MT7620 will
increase by 10 dB.

[1] https://lore.kernel.org/linux-wireless/TYAP286MB031571CDB146C414A908A66DBCFEA@TYAP286MB0315.JPNP286.PROD.OUTLOOK.COM/

Fixes: https://github.com/openwrt/openwrt/issues/11036
Signed-off-by: Shiji Yang <yangshiji66 at qq.com>
---

The relevant code can be found here. It's not a permanent link so I
don't want to add it to the commit message.
https://github.com/hanwckf/rt-n56u/blob/23387b278a7cf728748af606760758f5d59d1451/trunk/proprietary/rt_wifi/rtsoc/2.7.X.X/rt2860v2/common/cmm_sync.c#L470

 ...ifi-rt2x00-fix-MT7620-low-RSSI-issue.patch | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 package/kernel/mac80211/patches/rt2x00/999-wifi-rt2x00-fix-MT7620-low-RSSI-issue.patch

diff --git a/package/kernel/mac80211/patches/rt2x00/999-wifi-rt2x00-fix-MT7620-low-RSSI-issue.patch b/package/kernel/mac80211/patches/rt2x00/999-wifi-rt2x00-fix-MT7620-low-RSSI-issue.patch
new file mode 100644
index 0000000000..8f7343d14e
--- /dev/null
+++ b/package/kernel/mac80211/patches/rt2x00/999-wifi-rt2x00-fix-MT7620-low-RSSI-issue.patch
@@ -0,0 +1,39 @@
+From: Shiji Yang <yangshiji66 at outlook.com>
+Date: Sat, 23 Sep 2023 07:51:39 +0800
+Subject: [PATCH] wifi: rt2x00: fix MT7620 low RSSI issue
+
+On Mediatek vendor driver[1], MT7620 (RT6352) uses different RSSI
+base value '-2' compared to the other RT2x00 chips. This patch
+introduces the SoC specific base value to fix the low RSSI value
+reports on MT7620.
+
+[1] Found on MT76x2E_MT7620_LinuxAP_V3.0.4.0_P3 ConvertToRssi().
+
+Signed-off-by: Shiji Yang <yangshiji66 at outlook.com>
+---
+ drivers/net/wireless/ralink/rt2x00/rt2800lib.c | 7 ++++---
+ 1 file changed, 4 insertions(+), 3 deletions(-)
+
+--- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
++++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
+@@ -875,6 +875,7 @@ static int rt2800_agc_to_rssi(struct rt2
+ 	s8 rssi0 = rt2x00_get_field32(rxwi_w2, RXWI_W2_RSSI0);
+ 	s8 rssi1 = rt2x00_get_field32(rxwi_w2, RXWI_W2_RSSI1);
+ 	s8 rssi2 = rt2x00_get_field32(rxwi_w2, RXWI_W2_RSSI2);
++	s8 base_val = rt2x00_rt(rt2x00dev, RT6352) ? -2 : -12;
+ 	u16 eeprom;
+ 	u8 offset0;
+ 	u8 offset1;
+@@ -899,9 +900,9 @@ static int rt2800_agc_to_rssi(struct rt2
+ 	 * If the value in the descriptor is 0, it is considered invalid
+ 	 * and the default (extremely low) rssi value is assumed
+ 	 */
+-	rssi0 = (rssi0) ? (-12 - offset0 - rt2x00dev->lna_gain - rssi0) : -128;
+-	rssi1 = (rssi1) ? (-12 - offset1 - rt2x00dev->lna_gain - rssi1) : -128;
+-	rssi2 = (rssi2) ? (-12 - offset2 - rt2x00dev->lna_gain - rssi2) : -128;
++	rssi0 = (rssi0) ? (base_val - offset0 - rt2x00dev->lna_gain - rssi0) : -128;
++	rssi1 = (rssi1) ? (base_val - offset1 - rt2x00dev->lna_gain - rssi1) : -128;
++	rssi2 = (rssi2) ? (base_val - offset2 - rt2x00dev->lna_gain - rssi2) : -128;
+ 
+ 	/*
+ 	 * mac80211 only accepts a single RSSI value. Calculating the
-- 
2.39.2