/*
 *  c 2001 PPC 64 Team, IBM Corp
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 * scan-log-data driver for PPC64  Todd Inglett <tinglett@vnet.ibm.com>
 *
 * When ppc64 hardware fails the service processor dumps internal state
 * of the system.  After a reboot the operating system can access a dump
 * of this data using this driver.  A dump exists if the device-tree
 * /chosen/ibm,scan-log-data property exists.
 *
 * This driver exports /proc/ppc64/scan-log-dump which can be read.
 * The driver supports only sequential reads.
 *
 * The driver looks at a write to the driver for the single word "reset".
 * If given, the driver will reset the scanlog so the platform can free it.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <asm/rtas.h>
#include <asm/prom.h>

#define MODULE_VERS "1.0"
#define MODULE_NAME "scanlog"

/* Status returns from ibm,scan-log-dump */
#define SCANLOG_COMPLETE 0
#define SCANLOG_HWERROR -1
#define SCANLOG_CONTINUE 1

#define DEBUG(A...) do { if (scanlog_debug) printk(KERN_ERR "scanlog: " A); } while (0)

static int scanlog_debug;
static unsigned int ibm_scan_log_dump;                  /* RTAS token */
static struct proc_dir_entry *proc_ppc64_scan_log_dump; /* The proc file */

static ssize_t scanlog_read(struct file *file, char *buf,
                            size_t count, loff_t *ppos)
{
        struct inode * inode = file->f_dentry->d_inode;
        struct proc_dir_entry *dp;
        unsigned int *data;
        int status;
        unsigned long len, off;
        unsigned int wait_time;

        dp = PDE(inode);
        data = (unsigned int *)dp->data;

        if (!data) {
                printk(KERN_ERR "scanlog: read failed no data\n");
                return -EIO;
        }

        if (count > RTAS_DATA_BUF_SIZE)
                count = RTAS_DATA_BUF_SIZE;

        if (count < 1024) {
                /* This is the min supported by this RTAS call.  Rather
                 * than do all the buffering we insist the user code handle
                 * larger reads.  As long as cp works... :)
                 */
                printk(KERN_ERR "scanlog: cannot perform a small read (%ld)\n", count);
                return -EINVAL;
        }

        if (verify_area(VERIFY_WRITE, buf, count))
                return -EFAULT;

        for (;;) {
                wait_time = HZ/2;       /* default wait if no data */
                spin_lock(&rtas_data_buf_lock);
                memcpy(rtas_data_buf, data, RTAS_DATA_BUF_SIZE);
                status = rtas_call(ibm_scan_log_dump, 2, 1, NULL,
                                   (u32) __pa(rtas_data_buf), (u32) count);
                memcpy(data, rtas_data_buf, RTAS_DATA_BUF_SIZE);
                spin_unlock(&rtas_data_buf_lock);

                DEBUG("status=%d, data[0]=%x, data[1]=%x, data[2]=%x\n",
                      status, data[0], data[1], data[2]);
                switch (status) {
                    case SCANLOG_COMPLETE:
                        DEBUG("hit eof\n");
                        return 0;
                    case SCANLOG_HWERROR:
                        DEBUG("hardware error reading scan log data\n");
                        return -EIO;
                    case SCANLOG_CONTINUE:
                        /* We may or may not have data yet */
                        len = data[1];
                        off = data[2];
                        if (len > 0) {
                                if (copy_to_user(buf, ((char *)data)+off, len))
                                        return -EFAULT;
                                return len;
                        }
                        /* Break to sleep default time */
                        break;
                    default:
                        if (status > 9900 && status <= 9905) {
                                /* No data.  RTAS is hinting at a delay required
                                 * between 1-100000 milliseconds
                                 */
                                int ms = 1;
                                for (; status > 9900; status--)
                                        ms = ms * 10;
                                /* Use microseconds for reasonable accuracy */
                                ms *= 1000;
                                wait_time = ms / (1000000/HZ); /* round down is fine */
                                /* Fall through to sleep */
                        } else {
                                printk(KERN_ERR "scanlog: unknown error from rtas: %d\n", status);
                                return -EIO;
                        }
                }
                /* Apparently no data yet.  Wait and try again. */
                set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(wait_time);
        }
        /*NOTREACHED*/
}

static ssize_t scanlog_write(struct file * file, const char * buf,
                             size_t count, loff_t *ppos)
{
        char stkbuf[20];
        int status;

        if (count > 19) count = 19;
        if (copy_from_user (stkbuf, buf, count)) {
                return -EFAULT;
        }
        stkbuf[count] = 0;

        if (buf) {
                if (strncmp(stkbuf, "reset", 5) == 0) {
                        DEBUG("reset scanlog\n");
                        status = rtas_call(ibm_scan_log_dump, 2, 1, NULL, 0, 0);
                        DEBUG("rtas returns %d\n", status);
                } else if (strncmp(stkbuf, "debugon", 7) == 0) {
                        printk(KERN_ERR "scanlog: debug on\n");
                        scanlog_debug = 1;
                } else if (strncmp(stkbuf, "debugoff", 8) == 0) {
                        printk(KERN_ERR "scanlog: debug off\n");
                        scanlog_debug = 0;
                }
        }
        return count;
}

static int scanlog_open(struct inode * inode, struct file * file)
{
        struct proc_dir_entry *dp = PDE(inode);
        unsigned int *data = (unsigned int *)dp->data;

        if (!data) {
                printk(KERN_ERR "scanlog: open failed no data\n");
                return -EIO;
        }

        if (data[0] != 0) {
                /* This imperfect test stops a second copy of the
                 * data (or a reset while data is being copied)
                 */
                return -EBUSY;
        }

        data[0] = 0;    /* re-init so we restart the scan */

        return 0;
}

static int scanlog_release(struct inode * inode, struct file * file)
{
        struct proc_dir_entry *dp = PDE(inode);
        unsigned int *data = (unsigned int *)dp->data;

        if (!data) {
                printk(KERN_ERR "scanlog: release failed no data\n");
                return -EIO;
        }
        data[0] = 0;

        return 0;
}

struct file_operations scanlog_fops = {
        .owner          = THIS_MODULE,
        .read           = scanlog_read,
        .write          = scanlog_write,
        .open           = scanlog_open,
        .release        = scanlog_release,
};

int __init scanlog_init(void)
{
        struct proc_dir_entry *ent;

        ibm_scan_log_dump = rtas_token("ibm,scan-log-dump");
        if (ibm_scan_log_dump == RTAS_UNKNOWN_SERVICE) {
                printk(KERN_ERR "scan-log-dump not implemented on this system\n");
                return -EIO;
        }

        ent = create_proc_entry("ppc64/rtas/scan-log-dump",  S_IRUSR, NULL);
        if (ent) {
                ent->proc_fops = &scanlog_fops;
                /* Ideally we could allocate a buffer < 4G */
                ent->data = kmalloc(RTAS_DATA_BUF_SIZE, GFP_KERNEL);
                if (!ent->data) {
                        printk(KERN_ERR "Failed to allocate a buffer\n");
                        remove_proc_entry("scan-log-dump", ent->parent);
                        return -ENOMEM;
                }
                ((unsigned int *)ent->data)[0] = 0;
        } else {
                printk(KERN_ERR "Failed to create ppc64/scan-log-dump proc entry\n");
                return -EIO;
        }
        proc_ppc64_scan_log_dump = ent;

        return 0;
}

void __exit scanlog_cleanup(void)
{
        if (proc_ppc64_scan_log_dump) {
                if (proc_ppc64_scan_log_dump->data)
                        kfree(proc_ppc64_scan_log_dump->data);
                remove_proc_entry("scan-log-dump", proc_ppc64_scan_log_dump->parent);
        }
}

module_init(scanlog_init);
module_exit(scanlog_cleanup);
MODULE_LICENSE("GPL");