mac80211: limit MT7620 TX power based on eeprom calibration

This patch adds basic TX power control for the MT7620 and limits its
maximum TX power. This can avoid the link speed decrease caused by
chip overheating.

Signed-off-by: Shiji Yang <[email protected]>

package/kernel/mac80211/patches/rt2x00/997-wifi-rt2x00-limit-MT7620-TX-power-based-on-eeprom-ca.patch

@@ -0,0 +1,106 @@
+From: Shiji Yang <[email protected]>
+Date: Sat, 22 Jul 2023 21:56:30 +0800
+Subject: [PATCH] wifi: rt2x00: limit MT7620 TX power based on eeprom
+ calibration
+
+In the vendor driver, the current channel power is queried from
+EEPROM_TXPOWER_BG1 and EEPROM_TXPOWER_BG2. And then the mixed value
+will be written into the low half-word of the TX_ALC_CFG_0 register.
+The high half-word of the TX_ALC_CFG_0 is a fixed value 0x2f2f.
+
+We can't get the accurate TX power. Based on my tests and the new
+MediaTek mt76 driver source code, the real TX power is approximately
+equal to channel_power + (max) rate_power. Usually max rate_power is
+the gain of the OFDM 6M rate, which can be readed from the offset
+EEPROM_TXPOWER_BYRATE +1.
+
+Based on these eeprom values, this patch adds basic TX power control
+for the MT7620 and limits its maximum TX power. This can avoid the
+link speed decrease caused by chip overheating. rt2800_config_alc()
+function has also been renamed to rt2800_config_alc_rt6352() because
+it's only used by RT6352(MT7620).
+
+Notice:
+It's still need some work to sync the max channel power to the user
+interface. This part is missing from the rt2x00 driver structure. If
+we set the power exceed the calibration value, it won't take effect.
+
+Signed-off-by: Shiji Yang <[email protected]>
+---
+ .../net/wireless/ralink/rt2x00/rt2800lib.c    | 49 +++++++++++++------
+ 1 file changed, 34 insertions(+), 15 deletions(-)
+
+--- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
++++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
+@@ -3891,28 +3891,47 @@ static void rt2800_config_channel_rf7620
+ 	}
+ }
+ 
+-static void rt2800_config_alc(struct rt2x00_dev *rt2x00dev,
++static void rt2800_config_alc_rt6352(struct rt2x00_dev *rt2x00dev,
+ 			      struct ieee80211_channel *chan,
+ 			      int power_level) {
+-	u16 eeprom, target_power, max_power;
++	u16 eeprom, chan_power, rate_power, target_power;
++	u16 tx_power[2];
++	s8 *power_group[2];
+ 	u32 mac_sys_ctrl;
+-	u32 reg;
++	u32 cnt, reg;
+ 	u8 bbp;
+ 
+-	/* hardware unit is 0.5dBm, limited to 23.5dBm */
+-	power_level *= 2;
+-	if (power_level > 0x2f)
+-		power_level = 0x2f;
+-
+-	max_power = chan->max_power * 2;
+-	if (max_power > 0x2f)
+-		max_power = 0x2f;
++	/* get per channel power, 2 channels in total, unit is 0.5dBm */
++	power_level = (power_level - 3) * 2;
++	/*
++	 * We can't get the accurate TX power. Based on some tests, the real
++	 * TX power is approximately equal to channel_power + (max)rate_power.
++	 * Usually max rate_power is the gain of the OFDM 6M rate. The antenna
++	 * gain and externel PA gain are not included as we are unable to
++	 * obtain these values.
++	 */
++	rate_power = rt2800_eeprom_read_from_array(rt2x00dev,
++				EEPROM_TXPOWER_BYRATE, 1) & 0x3f;
++	power_level -= rate_power;
++	if (power_level < 1)
++		power_level = 1;
++	if (power_level > chan->max_power * 2)
++		power_level = chan->max_power * 2;
++
++	power_group[0] = rt2800_eeprom_addr(rt2x00dev, EEPROM_TXPOWER_BG1);
++	power_group[1] = rt2800_eeprom_addr(rt2x00dev, EEPROM_TXPOWER_BG2);
++	for (cnt = 0; cnt < 2; cnt++) {
++		chan_power = power_group[cnt][rt2x00dev->rf_channel - 1];
++		if (chan_power >= 0x20 || chan_power == 0)
++			chan_power = 0x10;
++		tx_power[cnt] = power_level < chan_power ? power_level : chan_power;
++	}
+ 
+ 	reg = rt2800_register_read(rt2x00dev, TX_ALC_CFG_0);
+-	rt2x00_set_field32(&reg, TX_ALC_CFG_0_CH_INIT_0, power_level);
+-	rt2x00_set_field32(&reg, TX_ALC_CFG_0_CH_INIT_1, power_level);
+-	rt2x00_set_field32(&reg, TX_ALC_CFG_0_LIMIT_0, max_power);
+-	rt2x00_set_field32(&reg, TX_ALC_CFG_0_LIMIT_1, max_power);
++	rt2x00_set_field32(&reg, TX_ALC_CFG_0_CH_INIT_0, tx_power[0]);
++	rt2x00_set_field32(&reg, TX_ALC_CFG_0_CH_INIT_1, tx_power[1]);
++	rt2x00_set_field32(&reg, TX_ALC_CFG_0_LIMIT_0, 0x2f);
++	rt2x00_set_field32(&reg, TX_ALC_CFG_0_LIMIT_1, 0x2f);
+ 
+ 	eeprom = rt2800_eeprom_read(rt2x00dev, EEPROM_NIC_CONF1);
+ 	if (rt2x00_get_field16(eeprom, EEPROM_NIC_CONF1_INTERNAL_TX_ALC)) {
+@@ -5321,7 +5340,7 @@ static void rt2800_config_txpower_rt6352
+ 	rt2x00_set_field32(&pwreg, TX_PWR_CFG_9B_STBC_MCS7, t);
+ 	rt2800_register_write(rt2x00dev, TX_PWR_CFG_9, pwreg);
+ 
+-	rt2800_config_alc(rt2x00dev, chan, power_level);
++	rt2800_config_alc_rt6352(rt2x00dev, chan, power_level);
+ 
+ 	/* TODO: temperature compensation code! */
+ }