USB: Debug: Add centralized debug buffer for USB drivers

Add a centralized debug buffer which can log events from all USB
drivers in gadget directory. This will help in debugging issue
from first instance rather than enabling dynamic debug log and
reproducing again.

Change-Id: Id0285d30bf640a63d904f1dd02dcd061f1819359
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>

drivers/usb/gadget/Makefile

@@ -10,3 +10,4 @@ libcomposite-y			:= usbstring.o config.o epautoconf.o
 libcomposite-y			+= composite.o functions.o configfs.o u_f.o
 
 obj-$(CONFIG_USB_GADGET)	+= udc/ function/ legacy/
+obj-y				+= debug.o

drivers/usb/gadget/configfs.c

@@ -8,6 +8,7 @@
 #include "configfs.h"
 #include "u_f.h"
 #include "u_os_desc.h"
+#include "debug.h"
 
 #ifdef CONFIG_USB_CONFIGFS_UEVENT
 #include <linux/platform_device.h>
@@ -1747,6 +1748,8 @@ static int __init gadget_cfs_init(void)
 
 	config_group_init(&gadget_subsys.su_group);
 
+	debug_debugfs_init();
+
 	ret = configfs_register_subsystem(&gadget_subsys);
 
 #ifdef CONFIG_USB_CONFIGFS_UEVENT
@@ -1761,6 +1764,7 @@ module_init(gadget_cfs_init);
 
 static void __exit gadget_cfs_exit(void)
 {
+	debug_debugfs_exit();
 	configfs_unregister_subsystem(&gadget_subsys);
 #ifdef CONFIG_USB_CONFIGFS_UEVENT
 	if (!IS_ERR(android_class))

drivers/usb/gadget/debug.c

@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2015, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/rwlock.h>
+#include <linux/debugfs.h>
+
+#include "debug.h"
+
+#define dbg_inc(i) ((i+1) % DBG_MAX_MSG)
+
+#define ENABLE_EVENT_LOG 1
+unsigned int enable_event_log = ENABLE_EVENT_LOG;
+module_param(enable_event_log, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(enable_event_log, "enable event logging in debug buffer");
+
+static struct {
+	char buf[DBG_MAX_MSG][DBG_MSG_LEN];   /* buffer */
+	unsigned idx;   /* index */
+	rwlock_t lck;   /* lock */
+	struct dentry *root;
+} __maybe_unused dbg_buffer = {
+	.idx = 0,
+	.lck = __RW_LOCK_UNLOCKED(lck),
+	.root = NULL
+};
+
+void __maybe_unused put_timestamp(char *tbuf)
+{
+	unsigned long long t;
+	unsigned long nanosec_rem;
+	unsigned long flags;
+
+	write_lock_irqsave(&dbg_buffer.lck, flags);
+	t = cpu_clock(smp_processor_id());
+	write_unlock_irqrestore(&dbg_buffer.lck, flags);
+	nanosec_rem = do_div(t, 1000000000)/1000;
+	snprintf(tbuf, TIME_BUF_LEN, "[%5lu.%06lu]: ", (unsigned long)t,
+		nanosec_rem);
+}
+
+void __maybe_unused add_event_to_buf(char *tbuf)
+{
+	unsigned long flags;
+	char *buf;
+	write_lock_irqsave(&dbg_buffer.lck, flags);
+	buf = dbg_buffer.buf[dbg_buffer.idx];
+	memcpy(buf, tbuf, DBG_MSG_LEN);
+	dbg_buffer.idx = (dbg_buffer.idx + 1) % DBG_MAX_MSG;
+	write_unlock_irqrestore(&dbg_buffer.lck, flags);
+}
+
+static int dbg_read_buf_show(struct seq_file *s, void *unused)
+{
+	unsigned long	flags;
+	unsigned	i;
+
+	read_lock_irqsave(&dbg_buffer.lck, flags);
+
+	i = dbg_buffer.idx;
+	if (strnlen(dbg_buffer.buf[i], DBG_MSG_LEN))
+		seq_printf(s, "%s\n", dbg_buffer.buf[i]);
+	for (i = dbg_inc(i); i != dbg_buffer.idx;  i = dbg_inc(i)) {
+		if (!strnlen(dbg_buffer.buf[i], DBG_MSG_LEN))
+			continue;
+		seq_printf(s, "%s\n", dbg_buffer.buf[i]);
+	}
+
+	read_unlock_irqrestore(&dbg_buffer.lck, flags);
+
+	return 0;
+}
+
+static int dbg_read_buf_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, dbg_read_buf_show, inode->i_private);
+}
+
+const struct file_operations dbg_read_buf_fops = {
+	.open			= dbg_read_buf_open,
+	.read			= seq_read,
+	.llseek			= seq_lseek,
+	.release		= single_release,
+};
+
+int debug_debugfs_init(void)
+{
+	struct dentry		*root;
+	struct dentry		*file;
+	int			ret;
+
+	root = debugfs_create_dir("debug", NULL);
+	if (!root) {
+		ret = -ENOMEM;
+		goto err0;
+	}
+
+	dbg_buffer.root = root;
+
+	file = debugfs_create_file("read_buf", S_IRUGO, root,
+			NULL, &dbg_read_buf_fops);
+	if (!file) {
+		ret = -ENOMEM;
+		goto err1;
+	}
+
+	return 0;
+
+err1:
+	debugfs_remove_recursive(root);
+
+err0:
+	return ret;
+}
+
+void debug_debugfs_exit(void)
+{
+	debugfs_remove_recursive(dbg_buffer.root);
+	dbg_buffer.root = NULL;
+}

drivers/usb/gadget/debug.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2015-2016, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __DEBUG_H_
+#define __DEBUG_H_
+
+#define DBG_MAX_MSG   1024UL
+#define DBG_MSG_LEN   80UL
+#define TIME_BUF_LEN  17
+#define DBG_EVENT_LEN  (DBG_MSG_LEN - TIME_BUF_LEN)
+
+extern unsigned int enable_event_log;
+extern void put_timestamp(char *tbuf);
+extern void add_event_to_buf(char *tbuf);
+extern int debug_debugfs_init(void);
+extern void debug_debugfs_exit(void);
+
+#define LOGLEVEL_NONE 8
+#define LOGLEVEL_DEBUG 7
+#define LOGLEVEL_INFO 6
+#define LOGLEVEL_ERR 3
+
+#define log_event(log_level, x...)					\
+do {									\
+	char buf[DBG_MSG_LEN];						\
+	if (log_level == LOGLEVEL_DEBUG)				\
+		pr_debug(x);						\
+	else if (log_level == LOGLEVEL_ERR)				\
+		pr_err(x);						\
+	else if (log_level == LOGLEVEL_INFO)				\
+		pr_info(x);						\
+	if (enable_event_log) {						\
+		put_timestamp(buf);					\
+		snprintf(&buf[TIME_BUF_LEN - 1], DBG_EVENT_LEN, x);	\
+		add_event_to_buf(buf);					\
+	}								\
+} while (0)
+
+#define log_event_none(x, ...) log_event(LOGLEVEL_NONE, x, ##__VA_ARGS__)
+#define log_event_dbg(x, ...) log_event(LOGLEVEL_DEBUG, x, ##__VA_ARGS__)
+#define log_event_err(x, ...) log_event(LOGLEVEL_ERR, x, ##__VA_ARGS__)
+#define log_event_info(x, ...) log_event(LOGLEVEL_INFO, x, ##__VA_ARGS__)
+
+#endif	/* __DEBUG_H_ */