wifi: rtw88: 8821cu: Fix firmware upload fail

RTL8822CU, RTL8822BU, and RTL8821CU need an extra register write after
reading and writing certain addresses.

Without this, the firmware upload fails approximately more than 50% of
the time.

Tested with RTL8811CU (Tenda U9 V2.0) which is the same as RTL8821CU
but without Bluetooth.

Fixes: a82dfd33 ("wifi: rtw88: Add common USB chip support")
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/f12ed39d-28e8-4b8b-8d22-447bcf295afc@gmail.com

drivers/net/wireless/realtek/rtw88/usb.c

@@ -33,6 +33,36 @@ static void rtw_usb_fill_tx_checksum(struct rtw_usb *rtwusb,
 	rtw_tx_fill_txdesc_checksum(rtwdev, &pkt_info, skb->data);
 }
 
+static void rtw_usb_reg_sec(struct rtw_dev *rtwdev, u32 addr, __le32 *data)
+{
+	struct rtw_usb *rtwusb = rtw_get_usb_priv(rtwdev);
+	struct usb_device *udev = rtwusb->udev;
+	bool reg_on_section = false;
+	u16 t_reg = 0x4e0;
+	u8 t_len = 1;
+	int status;
+
+	/* There are three sections:
+	 * 1. on (0x00~0xFF; 0x1000~0x10FF): this section is always powered on
+	 * 2. off (< 0xFE00, excluding "on" section): this section could be
+	 *    powered off
+	 * 3. local (>= 0xFE00): usb specific registers section
+	 */
+	if (addr <= 0xff || (addr >= 0x1000 && addr <= 0x10ff))
+		reg_on_section = true;
+
+	if (!reg_on_section)
+		return;
+
+	status = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+				 RTW_USB_CMD_REQ, RTW_USB_CMD_WRITE,
+				 t_reg, 0, data, t_len, 500);
+
+	if (status != t_len && status != -ENODEV)
+		rtw_err(rtwdev, "%s: reg 0x%x, usb write %u fail, status: %d\n",
+			__func__, t_reg, t_len, status);
+}
+
 static u32 rtw_usb_read(struct rtw_dev *rtwdev, u32 addr, u16 len)
 {
 	struct rtw_usb *rtwusb = rtw_get_usb_priv(rtwdev);
@@ -58,6 +88,11 @@ static u32 rtw_usb_read(struct rtw_dev *rtwdev, u32 addr, u16 len)
 		rtw_err(rtwdev, "read register 0x%x failed with %d\n",
 			addr, ret);
 
+	if (rtwdev->chip->id == RTW_CHIP_TYPE_8822C ||
+	    rtwdev->chip->id == RTW_CHIP_TYPE_8822B ||
+	    rtwdev->chip->id == RTW_CHIP_TYPE_8821C)
+		rtw_usb_reg_sec(rtwdev, addr, data);
+
 	return le32_to_cpu(*data);
 }
 
@@ -102,6 +137,11 @@ static void rtw_usb_write(struct rtw_dev *rtwdev, u32 addr, u32 val, int len)
 	if (ret < 0 && ret != -ENODEV && count++ < 4)
 		rtw_err(rtwdev, "write register 0x%x failed with %d\n",
 			addr, ret);
+
+	if (rtwdev->chip->id == RTW_CHIP_TYPE_8822C ||
+	    rtwdev->chip->id == RTW_CHIP_TYPE_8822B ||
+	    rtwdev->chip->id == RTW_CHIP_TYPE_8821C)
+		rtw_usb_reg_sec(rtwdev, addr, data);
 }
 
 static void rtw_usb_write8(struct rtw_dev *rtwdev, u32 addr, u8 val)