[PATCH rtw-next v2 1/1] wifi: rtw89: usb: Support switching to USB 3 mode

[Devin Wittmayer <lucid_duck@justthetip.ca>]

From: Bitterblue Smith <rtl8821cerfe2@gmail.com>

The Realtek wifi 6/7 devices which support USB 3 are weird: when first
plugged in, they pretend to be USB 2. The driver needs to send some
commands to the device, which make it disappear and come back as a
USB 3 device.

Implement the required commands in rtw89.

When a USB 3 device is plugged into a USB 2 port, rtw89 will try to
switch it to USB 3 mode only once. The device will disappear and come
back still in USB 2 mode, of course.

Some people experience heavy interference in the 2.4 GHz band in
USB 3 mode, so add a module parameter switch_usb_mode with the
default value 1 to let people disable the switching.

Tested with RTL8832BU and RTL8832CU.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Signed-off-by: Devin Wittmayer <lucid_duck@justthetip.ca>
Tested-by: Devin Wittmayer <lucid_duck@justthetip.ca>
---
 drivers/net/wireless/realtek/rtw89/reg.h |  4 +++
 drivers/net/wireless/realtek/rtw89/usb.c | 41 ++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw89/reg.h b/drivers/net/wireless/realtek/rtw89/reg.h
index 42ffe83931a3..7d4c085d9fb2 100644
--- a/drivers/net/wireless/realtek/rtw89/reg.h
+++ b/drivers/net/wireless/realtek/rtw89/reg.h
@@ -164,6 +164,10 @@
 #define R_AX_DBG_PORT_SEL 0x00C0
 #define B_AX_DEBUG_ST_MASK GENMASK(31, 0)
 
+#define R_AX_PAD_CTRL2 0x00C4
+#define U2SWITCHU3 0xB
+#define USB_SWITCH_DELAY 0xF
+
 #define R_AX_PMC_DBG_CTRL2 0x00CC
 #define B_AX_SYSON_DIS_PMCR_AX_WRMSK BIT(2)
 
diff --git a/drivers/net/wireless/realtek/rtw89/usb.c b/drivers/net/wireless/realtek/rtw89/usb.c
index 767a95f759b1..4fb25791d118 100644
--- a/drivers/net/wireless/realtek/rtw89/usb.c
+++ b/drivers/net/wireless/realtek/rtw89/usb.c
@@ -9,6 +9,11 @@
 #include "txrx.h"
 #include "usb.h"
 
+static bool rtw89_switch_usb_mode = true;
+module_param_named(switch_usb_mode, rtw89_switch_usb_mode, bool, 0644);
+MODULE_PARM_DESC(switch_usb_mode,
+		 "Set to N to disable switching to USB 3 mode to avoid potential interference in the 2.4 GHz band (default: Y)");
+
 static void rtw89_usb_read_port_complete(struct urb *urb);
 
 static void rtw89_usb_vendorreq(struct rtw89_dev *rtwdev, u32 addr,
@@ -1027,6 +1032,35 @@ static void rtw89_usb_intf_deinit(struct rtw89_dev *rtwdev,
 	usb_set_intfdata(intf, NULL);
 }
 
+static int rtw89_usb_switch_mode(struct rtw89_dev *rtwdev)
+{
+	struct rtw89_usb *rtwusb = rtw89_usb_priv(rtwdev);
+
+	if (!rtw89_switch_usb_mode)
+		return 0;
+
+	/* No known USB 3 devices with this chip. */
+	if (rtwdev->chip->chip_id == RTL8851B)
+		return 0;
+
+	if (rtwusb->udev->speed == USB_SPEED_SUPER)
+		return 0;
+
+	rtw89_debug(rtwdev, RTW89_DBG_HCI, "%s: pad_ctrl2: %#x %#x\n",
+		    __func__,
+		    rtw89_read8(rtwdev, R_AX_PAD_CTRL2 + 1),
+		    rtw89_read8(rtwdev, R_AX_PAD_CTRL2 + 2));
+
+	/* Already tried to switch but it's a USB 2 port. */
+	if (rtw89_read8(rtwdev, R_AX_PAD_CTRL2 + 1) == USB_SWITCH_DELAY)
+		return 0;
+
+	rtw89_write8(rtwdev, R_AX_PAD_CTRL2 + 1, USB_SWITCH_DELAY);
+	rtw89_write8(rtwdev, R_AX_PAD_CTRL2 + 2, U2SWITCHU3);
+
+	return 1;
+}
+
 int rtw89_usb_probe(struct usb_interface *intf,
 		    const struct usb_device_id *id)
 {
@@ -1059,6 +1093,13 @@ int rtw89_usb_probe(struct usb_interface *intf,
 		goto err_free_hw;
 	}
 
+	ret = rtw89_usb_switch_mode(rtwdev);
+	if (ret) {
+		/* Not a fail, but we do need to skip rtw89_core_register. */
+		ret = 0;
+		goto err_intf_deinit;
+	}
+
 	if (rtwusb->udev->speed == USB_SPEED_SUPER)
 		rtwdev->hci.dle_type = RTW89_HCI_DLE_TYPE_USB3;
 	else
-- 
2.53.0