wifi: mt76: mt7996: Use tx_power from default fw if EEPROM contains 0s

Some Banana Pi BPI-R4-NIC-BE14 WiFi modules are sold with zeros instead
of usable tx_power values in EEPROM for 2.4 GHz and 5 GHz bands.

This patch replaces tx_power zeros with default values from firmware
files while keeping the rest of the EEPROM data intact (including valid
6 GHz tx_power table).

Signed-off-by: Ivan Mironov <mironov.ivan@gmail.com>
Cc: stable@vger.kernel.org
Fixes: 98686cd21624 ("wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices")
Closes: openwrt/openwrt#17489
Link: openwrt#954

Author: im-0

mt7996/eeprom.c

@@ -95,6 +95,36 @@ mt7996_eeprom_parse_stream(const u8 *eeprom, u8 band_idx, u8 *path,
 	}
 }
 
+static void
+mt7996_eeprom_fixup_tx_power(struct mt7996_dev *dev, const u8 *def)
+{
+	u8 *eeprom = dev->mt76.eeprom.data;
+	int i;
+	bool zeros_detected = false;
+
+	if (!eeprom[MT_EE_TX0_POWER_2G]) {
+		eeprom[MT_EE_TX0_POWER_2G] = def[MT_EE_TX0_POWER_2G];
+		zeros_detected = true;
+	}
+
+	for (i = MT_EE_TX0_POWER_5G; i < MT_EE_TX0_POWER_5G + 5; ++i) {
+		if (!eeprom[i]) {
+			eeprom[i] = def[i];
+			zeros_detected = true;
+		}
+	}
+
+	for (i = MT_EE_TX0_POWER_6G; i < MT_EE_TX0_POWER_6G + 8; ++i) {
+		if (!eeprom[i]) {
+			eeprom[i] = def[i];
+			zeros_detected = true;
+		}
+	}
+
+	if (zeros_detected)
+		dev_warn(dev->mt76.dev, "eeprom tx_power zeros detected, using defaults\n");
+}
+
 static bool mt7996_eeprom_variant_valid(struct mt7996_dev *dev, const u8 *def)
 {
 #define FEM_INT	0
@@ -150,6 +180,8 @@ mt7996_eeprom_check_or_use_default(struct mt7996_dev *dev, bool use_default)
 		goto out;
 	}
 
+	mt7996_eeprom_fixup_tx_power(dev, fw->data);
+
 	if (!use_default && mt7996_eeprom_variant_valid(dev, fw->data))
 		goto out;