wifi: rt2x00: improve MT7620 register initialization

1. Do not hard reset the BBP. We can use soft reset instead. This
change has some help to the calibration failure issue.
2. Enable falling back to legacy rate from the HT/RTS rate by
setting the HT_FBK_TO_LEGACY register.
3. Implement MCS rate specific maximum PSDU size. It can improve
the transmission quality under the low RSSI condition.
4. Set BBP_84 register value to 0x19. This is used for extension
channel overlapping IOT.

Signed-off-by: Shiji Yang <[e-mail]>
Acked-by: Stanislaw Gruszka <[e-mail]>
Signed-off-by: Kalle Valo <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/net/wireless/ralink/rt2x00/rt2800.h

···
 #define LED_CFG_LED_POLAR		FIELD32(0x40000000)
 
 /*
+ * AMPDU_MAX_LEN_20M1S: Per MCS max A-MPDU length, 20 MHz, MCS 0-7
+ * AMPDU_MAX_LEN_20M2S: Per MCS max A-MPDU length, 20 MHz, MCS 8-15
+ * AMPDU_MAX_LEN_40M1S: Per MCS max A-MPDU length, 40 MHz, MCS 0-7
+ * AMPDU_MAX_LEN_40M2S: Per MCS max A-MPDU length, 40 MHz, MCS 8-15
+ * Maximum A-MPDU length = 2^(AMPDU_MAX - 5) kilobytes
+ */
+#define AMPDU_MAX_LEN_20M1S		0x1030
+#define AMPDU_MAX_LEN_20M2S		0x1034
+#define AMPDU_MAX_LEN_40M1S		0x1038
+#define AMPDU_MAX_LEN_40M2S		0x103C
+
+/*
  * AMPDU_BA_WINSIZE: Force BlockAck window size
  * FORCE_WINSIZE_ENABLE:
  *   0: Disable forcing of BlockAck window size
···
  * EXP_ACK_TIME:
  */
 #define EXP_ACK_TIME			0x1380
+
+/*
+ * HT_FBK_TO_LEGACY: Enable/Disable HT/RTS fallback to OFDM/CCK rate
+ * Not available for legacy SoCs
+ */
+#define HT_FBK_TO_LEGACY		0x1384
 
 /* TX_PWR_CFG_5 */
 #define TX_PWR_CFG_5			0x1384

drivers/net/wireless/ralink/rt2x00/rt2800lib.c

···
 	struct rt2800_drv_data *drv_data = rt2x00dev->drv_data;
 	u32 reg;
 	u16 eeprom;
+	u8 bbp;
 	unsigned int i;
 	int ret;
 
···
 	ret = rt2800_drv_init_registers(rt2x00dev);
 	if (ret)
 		return ret;
+
+	if (rt2x00_rt(rt2x00dev, RT6352)) {
+		rt2800_register_write(rt2x00dev, MAC_SYS_CTRL, 0x01);
+
+		bbp = rt2800_bbp_read(rt2x00dev, 21);
+		bbp |= 0x01;
+		rt2800_bbp_write(rt2x00dev, 21, bbp);
+		bbp = rt2800_bbp_read(rt2x00dev, 21);
+		bbp &= (~0x01);
+		rt2800_bbp_write(rt2x00dev, 21, bbp);
+
+		rt2800_register_write(rt2x00dev, MAC_SYS_CTRL, 0x00);
+	}
 
 	rt2800_register_write(rt2x00dev, LEGACY_BASIC_RATE, 0x0000013f);
 	rt2800_register_write(rt2x00dev, HT_BASIC_RATE, 0x00008003);
···
 		reg = rt2800_register_read(rt2x00dev, TX_ALC_CFG_1);
 		rt2x00_set_field32(&reg, TX_ALC_CFG_1_ROS_BUSY_EN, 0);
 		rt2800_register_write(rt2x00dev, TX_ALC_CFG_1, reg);
+
+		rt2800_register_write(rt2x00dev, AMPDU_MAX_LEN_20M1S, 0x77754433);
+		rt2800_register_write(rt2x00dev, AMPDU_MAX_LEN_20M2S, 0x77765543);
+		rt2800_register_write(rt2x00dev, AMPDU_MAX_LEN_40M1S, 0x77765544);
+		rt2800_register_write(rt2x00dev, AMPDU_MAX_LEN_40M2S, 0x77765544);
+
+		rt2800_register_write(rt2x00dev, HT_FBK_TO_LEGACY, 0x1010);
+
 	} else {
 		rt2800_register_write(rt2x00dev, TX_SW_CFG0, 0x00000000);
 		rt2800_register_write(rt2x00dev, TX_SW_CFG1, 0x00080606);
···
 	rt2800_bbp_dcoc_write(rt2x00dev, 159, 0x64);
 
 	rt2800_bbp4_mac_if_ctrl(rt2x00dev);
+
+	rt2800_bbp_write(rt2x00dev, 84, 0x19);
 }
 
 static void rt2800_init_bbp(struct rt2x00_dev *rt2x00dev)

drivers/net/wireless/ralink/rt2x00/rt2800mmio.c

···
 
 	rt2x00mmio_register_write(rt2x00dev, PWR_PIN_CFG, 0x00000003);
 
+	if (rt2x00_rt(rt2x00dev, RT6352))
+		return 0;
+
 	reg = 0;
 	rt2x00_set_field32(&reg, MAC_SYS_CTRL_RESET_CSR, 1);
 	rt2x00_set_field32(&reg, MAC_SYS_CTRL_RESET_BBP, 1);