/* Copyright (c) 2010-2011, 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/debugfs.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/types.h>

#include <asm/uaccess.h>

#include <mach/msm_iomap.h>

#include "rpm_log.h"

/* registers in MSM_RPM_LOG_PAGE_INDICES */
enum {
	MSM_RPM_LOG_TAIL,
	MSM_RPM_LOG_HEAD
};

/* used to 4 byte align message lengths */
#define PADDED_LENGTH(x) (0xFFFFFFFC & ((x) + 3))

/* calculates the character string length of a message of byte length x */
#define PRINTED_LENGTH(x) ((x) * 6 + 3)

/* number of ms to wait between checking for new messages in the RPM log */
#define RECHECK_TIME (50)

struct msm_rpm_log_buffer {
	char *data;
	u32 len;
	u32 pos;
	u32 max_len;
	u32 read_idx;
	struct msm_rpm_log_platform_data *pdata;
};

/******************************************************************************
 * Internal functions
 *****************************************************************************/

static inline u32
msm_rpm_log_read(const struct msm_rpm_log_platform_data *pdata, u32 page,
		 u32 reg)
{
	return readl_relaxed(pdata->reg_base + pdata->reg_offsets[page]
				+ reg * 4);
}

/*
 * msm_rpm_log_copy() - Copies messages from a volatile circular buffer in
 *			the RPM's shared memory into a private local buffer
 * msg_buffer:		pointer to local buffer (string)
 * buf_len:		length of local buffer in bytes
 * read_start_idx:	index into shared memory buffer
 *
 * Return value:	number of bytes written to the local buffer
 *
 * Copies messages stored in a circular buffer in the RPM Message Memory into
 * a specified local buffer.  The RPM processor is unaware of these reading
 * efforts, so care is taken to make sure that messages are valid both before
 * and after reading.  The RPM processor utilizes a ULog driver to write the
 * log.  The RPM processor maintains tail and head indices.  These correspond
 * to the next byte to write into, and the first valid byte, respectively.
 * Both indices increase monotonically (except for rollover).
 *
 * Messages take the form of [(u32)length] [(char)data0,1,...] in which the
 * length specifies the number of payload bytes.  Messages must be 4 byte
 * aligned, so padding is added at the end of a message as needed.
 *
 * Print format:
 * - 0xXX, 0xXX, 0xXX
 * - 0xXX
 * etc...
 */
static u32 msm_rpm_log_copy(const struct msm_rpm_log_platform_data *pdata,
			    char *msg_buffer, u32 buf_len, u32 *read_idx)
{
	u32 head_idx, tail_idx;
	u32 pos = 0;
	u32 i = 0;
	u32 msg_len;
	u32 pos_start;
	char temp[4];

	tail_idx = msm_rpm_log_read(pdata, MSM_RPM_LOG_PAGE_INDICES,
				    MSM_RPM_LOG_TAIL);
	head_idx = msm_rpm_log_read(pdata, MSM_RPM_LOG_PAGE_INDICES,
				    MSM_RPM_LOG_HEAD);

	/* loop while the remote buffer has valid messages left to read */
	while (tail_idx - head_idx > 0 && tail_idx - *read_idx > 0) {
		head_idx = msm_rpm_log_read(pdata, MSM_RPM_LOG_PAGE_INDICES,
					    MSM_RPM_LOG_HEAD);
		/* check if the message to be read is valid */
		if (tail_idx - *read_idx > tail_idx - head_idx) {
			*read_idx = head_idx;
			continue;
		}
		/*
		 * Ensure that all indices are 4 byte aligned.
		 * This conditions is required to interact with a ULog buffer
		 * properly.
		 */
		if (!IS_ALIGNED((tail_idx | head_idx | *read_idx), 4))
			break;

		msg_len = msm_rpm_log_read(pdata, MSM_RPM_LOG_PAGE_BUFFER,
					(*read_idx >> 2) & pdata->log_len_mask);

		/* handle messages that claim to be longer than the log */
		if (PADDED_LENGTH(msg_len) > tail_idx - *read_idx - 4)
			msg_len = tail_idx - *read_idx - 4;

		/* check that the local buffer has enough space for this msg */
		if (pos + PRINTED_LENGTH(msg_len) > buf_len)
			break;

		pos_start = pos;
		pos += scnprintf(msg_buffer + pos, buf_len - pos, "- ");

		/* copy message payload to local buffer */
		for (i = 0; i < msg_len; i++) {
			/* read from shared memory 4 bytes at a time */
			if (IS_ALIGNED(i, 4))
				*((u32 *)temp) = msm_rpm_log_read(pdata,
						MSM_RPM_LOG_PAGE_BUFFER,
						((*read_idx + 4 + i) >> 2) &
							pdata->log_len_mask);

			pos += scnprintf(msg_buffer + pos, buf_len - pos,
					 "0x%02X, ", temp[i & 0x03]);
		}

		pos += scnprintf(msg_buffer + pos, buf_len - pos, "\n");

		head_idx = msm_rpm_log_read(pdata, MSM_RPM_LOG_PAGE_INDICES,
					    MSM_RPM_LOG_HEAD);

		/* roll back if message that was read is not still valid */
		if (tail_idx - *read_idx > tail_idx - head_idx)
			pos = pos_start;

		*read_idx += PADDED_LENGTH(msg_len) + 4;
	}

	return pos;
}


/*
 * msm_rpm_log_file_read() - Reads in log buffer messages then outputs them to a
 *			     user buffer
 *
 * Return value:
 *	0:	 success
 *	-ENOMEM: no memory available
 *	-EINVAL: user buffer null or requested bytes 0
 *	-EFAULT: user buffer not writeable
 *	-EAGAIN: no bytes available at the moment
 */
static ssize_t msm_rpm_log_file_read(struct file *file, char __user *bufu,
				     size_t count, loff_t *ppos)
{
	u32 out_len, remaining;
	struct msm_rpm_log_platform_data *pdata;
	struct msm_rpm_log_buffer *buf;

	buf = file->private_data;
	pdata = buf->pdata;
	if (!pdata)
		return -EINVAL;
	if (!buf)
		return -ENOMEM;
	if (!buf->data)
		return -ENOMEM;
	if (!bufu || count < 0)
		return -EINVAL;
	if (!access_ok(VERIFY_WRITE, bufu, count))
		return -EFAULT;

	/* check for more messages if local buffer empty */
	if (buf->pos == buf->len) {
		buf->pos = 0;
		buf->len = msm_rpm_log_copy(pdata, buf->data, buf->max_len,
						&(buf->read_idx));
	}

	if ((file->f_flags & O_NONBLOCK) && buf->len == 0)
		return -EAGAIN;

	/* loop until new messages arrive */
	while (buf->len == 0) {
		cond_resched();
		if (msleep_interruptible(RECHECK_TIME))
			break;
		buf->len = msm_rpm_log_copy(pdata, buf->data, buf->max_len,
						&(buf->read_idx));
	}

	out_len = ((buf->len - buf->pos) < count ? buf->len - buf->pos : count);

	remaining = __copy_to_user(bufu, &(buf->data[buf->pos]), out_len);
	buf->pos += out_len - remaining;

	return out_len - remaining;
}


/*
 * msm_rpm_log_file_open() - Allows a new reader to open the RPM log virtual
 *                           file
 *
 * One local buffer is kmalloc'ed for each reader, so no resource sharing has
 * to take place (besides the read only access to the RPM log buffer).
 *
 * Return value:
 *	0:	 success
 *	-ENOMEM: no memory available
 */
static int msm_rpm_log_file_open(struct inode *inode, struct file *file)
{
	struct msm_rpm_log_buffer *buf;
	struct msm_rpm_log_platform_data *pdata;

	pdata = inode->i_private;
	if (!pdata)
		return -EINVAL;

	file->private_data =
		   kmalloc(sizeof(struct msm_rpm_log_buffer), GFP_KERNEL);
	if (!file->private_data) {
		pr_err("%s: ERROR kmalloc failed to allocate %d bytes\n",
			__func__, sizeof(struct msm_rpm_log_buffer));
		return -ENOMEM;
	}
	buf = file->private_data;

	buf->data = kmalloc(PRINTED_LENGTH(pdata->log_len), GFP_KERNEL);
	if (!buf->data) {
		kfree(file->private_data);
		file->private_data = NULL;
		pr_err("%s: ERROR kmalloc failed to allocate %d bytes\n",
			__func__, PRINTED_LENGTH(pdata->log_len));
		return -ENOMEM;
	}

	buf->pdata = pdata;
	buf->len = 0;
	buf->pos = 0;
	buf->max_len = PRINTED_LENGTH(pdata->log_len);
	buf->read_idx = msm_rpm_log_read(pdata, MSM_RPM_LOG_PAGE_INDICES,
					 MSM_RPM_LOG_HEAD);
	return 0;
}

static int msm_rpm_log_file_close(struct inode *inode, struct file *file)
{
	kfree(((struct msm_rpm_log_buffer *)file->private_data)->data);
	kfree(file->private_data);
	return 0;
}


static const struct file_operations msm_rpm_log_file_fops = {
	.owner   = THIS_MODULE,
	.open    = msm_rpm_log_file_open,
	.read    = msm_rpm_log_file_read,
	.release = msm_rpm_log_file_close,
};

static int msm_rpm_log_probe(struct platform_device *pdev)
{
	struct dentry *dent;
	struct msm_rpm_log_platform_data *pdata;

	pdata = pdev->dev.platform_data;
	if (!pdata)
		return -EINVAL;

	pdata->reg_base = ioremap(pdata->phys_addr_base, pdata->phys_size);
	if (!pdata->reg_base) {
		pr_err("%s: ERROR could not ioremap: start=%p, len=%u\n",
			__func__, (void *) pdata->phys_addr_base,
			pdata->phys_size);
		return -EBUSY;
	}

	dent = debugfs_create_file("rpm_log", S_IRUGO, NULL,
			pdev->dev.platform_data, &msm_rpm_log_file_fops);
	if (!dent) {
		pr_err("%s: ERROR debugfs_create_file failed\n", __func__);
		return -ENOMEM;
	}

	platform_set_drvdata(pdev, dent);

	pr_notice("%s: OK\n", __func__);
	return 0;
}

static int msm_rpm_log_remove(struct platform_device *pdev)
{
	struct dentry *dent;
	struct msm_rpm_log_platform_data *pdata;

	pdata = pdev->dev.platform_data;

	iounmap(pdata->reg_base);

	dent = platform_get_drvdata(pdev);
	debugfs_remove(dent);
	platform_set_drvdata(pdev, NULL);

	pr_notice("%s: OK\n", __func__);
	return 0;
}

static struct platform_driver msm_rpm_log_driver = {
	.probe		= msm_rpm_log_probe,
	.remove		= msm_rpm_log_remove,
	.driver		= {
		.name = "msm_rpm_log",
		.owner = THIS_MODULE,
	},
};

static int __init msm_rpm_log_init(void)
{
	return platform_driver_register(&msm_rpm_log_driver);
}

static void __exit msm_rpm_log_exit(void)
{
	platform_driver_unregister(&msm_rpm_log_driver);
}

module_init(msm_rpm_log_init);
module_exit(msm_rpm_log_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MSM RPM Log driver");
MODULE_VERSION("1.0");
MODULE_ALIAS("platform:msm_rpm_log");