[PATCH] rtw88: usb: retry control message on -EPROTO error

[VolcomIlluminated <volcomilluminated@tuta.com>]

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From: VolcomIlluminated <volcomilluminated@tuta.com>
Date: Wed, 28 May 2026 00:00:00 +0000
Subject: [PATCH] rtw88: usb: retry control message on -EPROTO error

USB control messages can transiently fail with -EPROTO (-71) during
device probe on some USB host controllers. This manifests as repeated
"write register failed with -71" errors during driver initialization.

Add a retry loop of up to 3 attempts with 10ms delay when -EPROTO is
returned from usb_control_msg. This recovers the transient error and
allows the driver to initialize cleanly.

Tested on RTL8822BU (Edimax EW-7822ULC) with clean boot and zero
probe errors.

Signed-off-by: VolcomIlluminated <volcomilluminated@tuta.com>
---
--- /tmp/linux-6.18/drivers/net/wireless/realtek/rtw88/usb.c	2025-11-30 17:42:10.000000000 -0500
+++ /home/ptpx86mm1/kernelbuild/linux-6.18/drivers/net/wireless/realtek/rtw88/usb.c	2026-05-24 20:06:27.798337237 -0400
@@ -140,6 +140,16 @@
 	ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
 			      RTW_USB_CMD_REQ, RTW_USB_CMD_WRITE,
 			      addr, 0, data, len, 500);
+	if (ret == -EPROTO) {
+		int retry;
+
+		for (retry = 0; retry < 3 && ret == -EPROTO; retry++) {
+			msleep(10);
+			ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+					      RTW_USB_CMD_REQ, RTW_USB_CMD_WRITE,
+					      addr, 0, data, len, 500);
+		}
+	}
 	if (ret < 0 && ret != -ENODEV && count++ < 4)
 		rtw_err(rtwdev, "write register 0x%x failed with %d\n",
 			addr, ret);