/*
 * Virtual Processor Dispatch Trace Log
 *
 * (C) Copyright IBM Corporation 2009
 *
 * Author: Jeremy Kerr <jk@ozlabs.org>
 *
 * 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, or (at your option)
 * any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/init.h>
#include <linux/debugfs.h>
#include <asm/smp.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/firmware.h>

#include "plpar_wrappers.h"

/*
 * Layout of entries in the hypervisor's DTL buffer. Although we don't
 * actually access the internals of an entry (we only need to know the size),
 * we might as well define it here for reference.
 */
struct dtl_entry {
        u8      dispatch_reason;
        u8      preempt_reason;
        u16     processor_id;
        u32     enqueue_to_dispatch_time;
        u32     ready_to_enqueue_time;
        u32     waiting_to_ready_time;
        u64     timebase;
        u64     fault_addr;
        u64     srr0;
        u64     srr1;
};

struct dtl {
        struct dtl_entry        *buf;
        struct dentry           *file;
        int                     cpu;
        int                     buf_entries;
        u64                     last_idx;
};
static DEFINE_PER_CPU(struct dtl, dtl);

/*
 * Dispatch trace log event mask:
 * 0x7: 0x1: voluntary virtual processor waits
 *      0x2: time-slice preempts
 *      0x4: virtual partition memory page faults
 */
static u8 dtl_event_mask = 0x7;


/*
 * Size of per-cpu log buffers. Default is just under 16 pages worth.
 */
static int dtl_buf_entries = (16 * 85);


static int dtl_enable(struct dtl *dtl)
{
        unsigned long addr;
        int ret, hwcpu;

        /* only allow one reader */
        if (dtl->buf)
                return -EBUSY;

        /* we need to store the original allocation size for use during read */
        dtl->buf_entries = dtl_buf_entries;

        dtl->buf = kmalloc_node(dtl->buf_entries * sizeof(struct dtl_entry),
                        GFP_KERNEL, cpu_to_node(dtl->cpu));
        if (!dtl->buf) {
                printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
                                __func__, dtl->cpu);
                return -ENOMEM;
        }

        /* Register our dtl buffer with the hypervisor. The HV expects the
         * buffer size to be passed in the second word of the buffer */
        ((u32 *)dtl->buf)[1] = dtl->buf_entries * sizeof(struct dtl_entry);

        hwcpu = get_hard_smp_processor_id(dtl->cpu);
        addr = __pa(dtl->buf);
        ret = register_dtl(hwcpu, addr);
        if (ret) {
                printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
                       "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
                kfree(dtl->buf);
                return -EIO;
        }

        /* set our initial buffer indices */
        dtl->last_idx = lppaca[dtl->cpu].dtl_idx = 0;

        /* ensure that our updates to the lppaca fields have occurred before
         * we actually enable the logging */
        smp_wmb();

        /* enable event logging */
        lppaca[dtl->cpu].dtl_enable_mask = dtl_event_mask;

        return 0;
}

static void dtl_disable(struct dtl *dtl)
{
        int hwcpu = get_hard_smp_processor_id(dtl->cpu);

        lppaca[dtl->cpu].dtl_enable_mask = 0x0;

        unregister_dtl(hwcpu, __pa(dtl->buf));

        kfree(dtl->buf);
        dtl->buf = NULL;
        dtl->buf_entries = 0;
}

/* file interface */

static int dtl_file_open(struct inode *inode, struct file *filp)
{
        struct dtl *dtl = inode->i_private;
        int rc;

        rc = dtl_enable(dtl);
        if (rc)
                return rc;

        filp->private_data = dtl;
        return 0;
}

static int dtl_file_release(struct inode *inode, struct file *filp)
{
        struct dtl *dtl = inode->i_private;
        dtl_disable(dtl);
        return 0;
}

static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
                loff_t *pos)
{
        int rc, cur_idx, last_idx, n_read, n_req, read_size;
        struct dtl *dtl;

        if ((len % sizeof(struct dtl_entry)) != 0)
                return -EINVAL;

        dtl = filp->private_data;

        /* requested number of entries to read */
        n_req = len / sizeof(struct dtl_entry);

        /* actual number of entries read */
        n_read = 0;

        cur_idx = lppaca[dtl->cpu].dtl_idx;
        last_idx = dtl->last_idx;

        if (cur_idx - last_idx > dtl->buf_entries) {
                pr_debug("%s: hv buffer overflow for cpu %d, samples lost\n",
                                __func__, dtl->cpu);
        }

        cur_idx  %= dtl->buf_entries;
        last_idx %= dtl->buf_entries;

        /* read the tail of the buffer if we've wrapped */
        if (last_idx > cur_idx) {
                read_size = min(n_req, dtl->buf_entries - last_idx);

                rc = copy_to_user(buf, &dtl->buf[last_idx],
                                read_size * sizeof(struct dtl_entry));
                if (rc)
                        return -EFAULT;

                last_idx = 0;
                n_req -= read_size;
                n_read += read_size;
                buf += read_size * sizeof(struct dtl_entry);
        }

        /* .. and now the head */
        read_size = min(n_req, cur_idx - last_idx);
        rc = copy_to_user(buf, &dtl->buf[last_idx],
                        read_size * sizeof(struct dtl_entry));
        if (rc)
                return -EFAULT;

        n_read += read_size;
        dtl->last_idx += n_read;

        return n_read * sizeof(struct dtl_entry);
}

static const struct file_operations dtl_fops = {
        .open           = dtl_file_open,
        .release        = dtl_file_release,
        .read           = dtl_file_read,
        .llseek         = no_llseek,
};

static struct dentry *dtl_dir;

static int dtl_setup_file(struct dtl *dtl)
{
        char name[10];

        sprintf(name, "cpu-%d", dtl->cpu);

        dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
        if (!dtl->file)
                return -ENOMEM;

        return 0;
}

static int dtl_init(void)
{
        struct dentry *event_mask_file, *buf_entries_file;
        int rc, i;

        if (!firmware_has_feature(FW_FEATURE_SPLPAR))
                return -ENODEV;

        /* set up common debugfs structure */

        rc = -ENOMEM;
        dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
        if (!dtl_dir) {
                printk(KERN_WARNING "%s: can't create dtl root dir\n",
                                __func__);
                goto err;
        }

        event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
                                dtl_dir, &dtl_event_mask);
        buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0600,
                                dtl_dir, &dtl_buf_entries);

        if (!event_mask_file || !buf_entries_file) {
                printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
                goto err_remove_dir;
        }

        /* set up the per-cpu log structures */
        for_each_possible_cpu(i) {
                struct dtl *dtl = &per_cpu(dtl, i);
                dtl->cpu = i;

                rc = dtl_setup_file(dtl);
                if (rc)
                        goto err_remove_dir;
        }

        return 0;

err_remove_dir:
        debugfs_remove_recursive(dtl_dir);
err:
        return rc;
}
arch_initcall(dtl_init);