usb: mtu3: add debugfs interface files

This adds more debugfs consumers. The debugfs entries read some
important registers, fifo status, QMU ring, endpoint status, and
IPPC probe interface to get internal status.
With these entries, users can check the registers, endpoint and
GPD used during run time.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/mtu3/Makefile

@@ -17,3 +17,7 @@ endif
 ifneq ($(CONFIG_USB_MTU3_DUAL_ROLE),)
 	mtu3-y	+= mtu3_dr.o
 endif
+
+ifneq ($(CONFIG_DEBUG_FS),)
+	mtu3-y	+= mtu3_debugfs.o
+endif

drivers/usb/mtu3/mtu3_core.c

@@ -16,6 +16,7 @@
 #include <linux/platform_device.h>
 
 #include "mtu3.h"
+#include "mtu3_debug.h"
 
 static int ep_fifo_alloc(struct mtu3_ep *mep, u32 seg_size)
 {
@@ -900,6 +901,8 @@ int ssusb_gadget_init(struct ssusb_mtk *ssusb)
 	if (mtu->ssusb->dr_mode == USB_DR_MODE_OTG)
 		mtu3_stop(mtu);
 
+	ssusb_dev_debugfs_init(ssusb);
+
 	dev_dbg(dev, " %s() done...\n", __func__);
 
 	return 0;

drivers/usb/mtu3/mtu3_debug.h

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * mtu3_debug.h - debug header
+ *
+ * Copyright (C) 2019 MediaTek Inc.
+ *
+ * Author: Chunfeng Yun <chunfeng.yun@mediatek.com>
+ */
+
+#ifndef __MTU3_DEBUG_H__
+#define __MTU3_DEBUG_H__
+
+#include <linux/debugfs.h>
+
+#define MTU3_DEBUGFS_NAME_LEN 32
+
+struct mtu3_regset {
+	char name[MTU3_DEBUGFS_NAME_LEN];
+	struct debugfs_regset32 regset;
+	size_t nregs;
+};
+
+struct mtu3_file_map {
+	const char *name;
+	int (*show)(struct seq_file *s, void *unused);
+};
+
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+void ssusb_dev_debugfs_init(struct ssusb_mtk *ssusb);
+void ssusb_debugfs_create_root(struct ssusb_mtk *ssusb);
+void ssusb_debugfs_remove_root(struct ssusb_mtk *ssusb);
+
+#else
+static inline void ssusb_dev_debugfs_init(struct ssusb_mtk *ssusb) {}
+static inline void ssusb_debugfs_create_root(struct ssusb_mtk *ssusb) {}
+static inline void ssusb_debugfs_remove_root(struct ssusb_mtk *ssusb) {}
+
+#endif /* CONFIG_DEBUG_FS */
+
+#endif /* __MTU3_DEBUG_H__ */