tile-srom.c

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/*
 * Copyright 2011 Tilera Corporation. 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
 *   as published by the Free Software Foundation, version 2.
 *
 *   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, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 *
 * SPI Flash ROM driver
 *
 * This source code is derived from code provided in "Linux Device
 * Drivers, Third Edition", by Jonathan Corbet, Alessandro Rubini, and
 * Greg Kroah-Hartman, published by O'Reilly Media, Inc.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h>   /* printk() */
#include <linux/slab.h>     /* kmalloc() */
#include <linux/fs.h>       /* everything... */
#include <linux/errno.h>    /* error codes */
#include <linux/types.h>    /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h>    /* O_ACCMODE */
#include <linux/aio.h>
#include <linux/pagemap.h>
#include <linux/hugetlb.h>
#include <linux/uaccess.h>
#include <linux/platform_device.h>
#include <hv/hypervisor.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/delay.h>
#include <hv/drv_srom_intf.h>

/*
 * Size of our hypervisor I/O requests.  We break up large transfers
 * so that we don't spend large uninterrupted spans of time in the
 * hypervisor.  Erasing an SROM sector takes a significant fraction of
 * a second, so if we allowed the user to, say, do one I/O to write the
 * entire ROM, we'd get soft lockup timeouts, or worse.
 */
#define SROM_CHUNK_SIZE ((size_t)4096)

/*
 * When hypervisor is busy (e.g. erasing), poll the status periodically.
 */

/*
 * Interval to poll the state in msec
 */
#define SROM_WAIT_TRY_INTERVAL 20

/*
 * Maximum times to poll the state
 */
#define SROM_MAX_WAIT_TRY_TIMES 1000

struct srom_dev {
    int hv_devhdl;          /* Handle for hypervisor device */
    u32 total_size;         /* Size of this device */
    u32 sector_size;        /* Size of a sector */
    u32 page_size;          /* Size of a page */
    struct mutex lock;      /* Allow only one accessor at a time */
};

static int srom_major;          /* Dynamic major by default */
module_param(srom_major, int, 0);
MODULE_AUTHOR("Tilera Corporation");
MODULE_LICENSE("GPL");

static int srom_devs;           /* Number of SROM partitions */
static struct cdev srom_cdev;
static struct class *srom_class;
static struct srom_dev *srom_devices;

/*
 * Handle calling the hypervisor and managing EAGAIN/EBUSY.
 */

static ssize_t _srom_read(int hv_devhdl, void *buf,
              loff_t off, size_t count)
{
    int retval, retries = SROM_MAX_WAIT_TRY_TIMES;
    for (;;) {
        retval = hv_dev_pread(hv_devhdl, 0, (HV_VirtAddr)buf,
                      count, off);
        if (retval >= 0)
            return retval;
        if (retval == HV_EAGAIN)
            continue;
        if (retval == HV_EBUSY && --retries > 0) {
            msleep(SROM_WAIT_TRY_INTERVAL);
            continue;
        }
        pr_err("_srom_read: error %d\n", retval);
        return -EIO;
    }
}

static ssize_t _srom_write(int hv_devhdl, const void *buf,
               loff_t off, size_t count)
{
    int retval, retries = SROM_MAX_WAIT_TRY_TIMES;
    for (;;) {
        retval = hv_dev_pwrite(hv_devhdl, 0, (HV_VirtAddr)buf,
                       count, off);
        if (retval >= 0)
            return retval;
        if (retval == HV_EAGAIN)
            continue;
        if (retval == HV_EBUSY && --retries > 0) {
            msleep(SROM_WAIT_TRY_INTERVAL);
            continue;
        }
        pr_err("_srom_write: error %d\n", retval);
        return -EIO;
    }
}

static int srom_open(struct inode *inode, struct file *filp)
{
    filp->private_data = &srom_devices[iminor(inode)];
    return 0;
}


static int srom_release(struct inode *inode, struct file *filp)
{
    struct srom_dev *srom = filp->private_data;
    char dummy;

    /* Make sure we've flushed anything written to the ROM. */
    mutex_lock(&srom->lock);
    if (srom->hv_devhdl >= 0)
        _srom_write(srom->hv_devhdl, &dummy, SROM_FLUSH_OFF, 1);
    mutex_unlock(&srom->lock);

    filp->private_data = NULL;

    return 0;
}


static ssize_t srom_read(struct file *filp, char __user *buf,
             size_t count, loff_t *f_pos)
{
    int retval = 0;
    void *kernbuf;
    struct srom_dev *srom = filp->private_data;

    kernbuf = kmalloc(SROM_CHUNK_SIZE, GFP_KERNEL);
    if (!kernbuf)
        return -ENOMEM;

    if (mutex_lock_interruptible(&srom->lock)) {
        retval = -ERESTARTSYS;
        kfree(kernbuf);
        return retval;
    }

    while (count) {
        int hv_retval;
        int bytes_this_pass = min(count, SROM_CHUNK_SIZE);

        hv_retval = _srom_read(srom->hv_devhdl, kernbuf,
                       *f_pos, bytes_this_pass);
        if (hv_retval <= 0) {
            if (retval == 0)
                retval = hv_retval;
            break;
        }

        if (copy_to_user(buf, kernbuf, hv_retval) != 0) {
            retval = -EFAULT;
            break;
        }

        retval += hv_retval;
        *f_pos += hv_retval;
        buf += hv_retval;
        count -= hv_retval;
    }

    mutex_unlock(&srom->lock);
    kfree(kernbuf);

    return retval;
}

static ssize_t srom_write(struct file *filp, const char __user *buf,
              size_t count, loff_t *f_pos)
{
    int retval = 0;
    void *kernbuf;
    struct srom_dev *srom = filp->private_data;

    kernbuf = kmalloc(SROM_CHUNK_SIZE, GFP_KERNEL);
    if (!kernbuf)
        return -ENOMEM;

    if (mutex_lock_interruptible(&srom->lock)) {
        retval = -ERESTARTSYS;
        kfree(kernbuf);
        return retval;
    }

    while (count) {
        int hv_retval;
        int bytes_this_pass = min(count, SROM_CHUNK_SIZE);

        if (copy_from_user(kernbuf, buf, bytes_this_pass) != 0) {
            retval = -EFAULT;
            break;
        }

        hv_retval = _srom_write(srom->hv_devhdl, kernbuf,
                    *f_pos, bytes_this_pass);
        if (hv_retval <= 0) {
            if (retval == 0)
                retval = hv_retval;
            break;
        }

        retval += hv_retval;
        *f_pos += hv_retval;
        buf += hv_retval;
        count -= hv_retval;
    }

    mutex_unlock(&srom->lock);
    kfree(kernbuf);

    return retval;
}

/* Provide our own implementation so we can use srom->total_size. */
loff_t srom_llseek(struct file *filp, loff_t offset, int origin)
{
    struct srom_dev *srom = filp->private_data;

    if (mutex_lock_interruptible(&srom->lock))
        return -ERESTARTSYS;

    switch (origin) {
    case SEEK_END:
        offset += srom->total_size;
        break;
    case SEEK_CUR:
        offset += filp->f_pos;
        break;
    }

    if (offset < 0 || offset > srom->total_size) {
        offset = -EINVAL;
    } else {
        filp->f_pos = offset;
        filp->f_version = 0;
    }

    mutex_unlock(&srom->lock);

    return offset;
}

static ssize_t total_show(struct device *dev,
              struct device_attribute *attr, char *buf)
{
    struct srom_dev *srom = dev_get_drvdata(dev);
    return sprintf(buf, "%u\n", srom->total_size);
}

static ssize_t sector_show(struct device *dev,
               struct device_attribute *attr, char *buf)
{
    struct srom_dev *srom = dev_get_drvdata(dev);
    return sprintf(buf, "%u\n", srom->sector_size);
}

static ssize_t page_show(struct device *dev,
             struct device_attribute *attr, char *buf)
{
    struct srom_dev *srom = dev_get_drvdata(dev);
    return sprintf(buf, "%u\n", srom->page_size);
}

static struct device_attribute srom_dev_attrs[] = {
    __ATTR(total_size, S_IRUGO, total_show, NULL),
    __ATTR(sector_size, S_IRUGO, sector_show, NULL),
    __ATTR(page_size, S_IRUGO, page_show, NULL),
    __ATTR_NULL
};

static char *srom_devnode(struct device *dev, umode_t *mode)
{
    *mode = S_IRUGO | S_IWUSR;
    return kasprintf(GFP_KERNEL, "srom/%s", dev_name(dev));
}

/*
 * The fops
 */
static const struct file_operations srom_fops = {
    .owner =     THIS_MODULE,
    .llseek =    srom_llseek,
    .read =      srom_read,
    .write =     srom_write,
    .open =      srom_open,
    .release =   srom_release,
};

static int srom_setup_minor(struct srom_dev *srom, int index)
{
    struct device *dev;
    int devhdl = srom->hv_devhdl;

    mutex_init(&srom->lock);

    if (_srom_read(devhdl, &srom->total_size,
               SROM_TOTAL_SIZE_OFF, sizeof(srom->total_size)) < 0)
        return -EIO;
    if (_srom_read(devhdl, &srom->sector_size,
               SROM_SECTOR_SIZE_OFF, sizeof(srom->sector_size)) < 0)
        return -EIO;
    if (_srom_read(devhdl, &srom->page_size,
               SROM_PAGE_SIZE_OFF, sizeof(srom->page_size)) < 0)
        return -EIO;

    dev = device_create(srom_class, &platform_bus,
                MKDEV(srom_major, index), srom, "%d", index);
    return IS_ERR(dev) ? PTR_ERR(dev) : 0;
}

static int srom_init(void)
{
    int result, i;
    dev_t dev = MKDEV(srom_major, 0);

    /*
     * Start with a plausible number of partitions; the krealloc() call
     * below will yield about log(srom_devs) additional allocations.
     */
    srom_devices = kzalloc(4 * sizeof(struct srom_dev), GFP_KERNEL);

    /* Discover the number of srom partitions. */
    for (i = 0; ; i++) {
        int devhdl;
        char buf[20];
        struct srom_dev *new_srom_devices =
            krealloc(srom_devices, (i+1) * sizeof(struct srom_dev),
                 GFP_KERNEL | __GFP_ZERO);
        if (!new_srom_devices) {
            result = -ENOMEM;
            goto fail_mem;
        }
        srom_devices = new_srom_devices;
        sprintf(buf, "srom/0/%d", i);
        devhdl = hv_dev_open((HV_VirtAddr)buf, 0);
        if (devhdl < 0) {
            if (devhdl != HV_ENODEV)
                pr_notice("srom/%d: hv_dev_open failed: %d.\n",
                      i, devhdl);
            break;
        }
        srom_devices[i].hv_devhdl = devhdl;
    }
    srom_devs = i;

    /* Bail out early if we have no partitions at all. */
    if (srom_devs == 0) {
        result = -ENODEV;
        goto fail_mem;
    }

    /* Register our major, and accept a dynamic number. */
    if (srom_major)
        result = register_chrdev_region(dev, srom_devs, "srom");
    else {
        result = alloc_chrdev_region(&dev, 0, srom_devs, "srom");
        srom_major = MAJOR(dev);
    }
    if (result < 0)
        goto fail_mem;

    /* Register a character device. */
    cdev_init(&srom_cdev, &srom_fops);
    srom_cdev.owner = THIS_MODULE;
    srom_cdev.ops = &srom_fops;
    result = cdev_add(&srom_cdev, dev, srom_devs);
    if (result < 0)
        goto fail_chrdev;

    /* Create a sysfs class. */
    srom_class = class_create(THIS_MODULE, "srom");
    if (IS_ERR(srom_class)) {
        result = PTR_ERR(srom_class);
        goto fail_cdev;
    }
    srom_class->dev_attrs = srom_dev_attrs;
    srom_class->devnode = srom_devnode;

    /* Do per-partition initialization */
    for (i = 0; i < srom_devs; i++) {
        result = srom_setup_minor(srom_devices + i, i);
        if (result < 0)
            goto fail_class;
    }

    return 0;

fail_class:
    for (i = 0; i < srom_devs; i++)
        device_destroy(srom_class, MKDEV(srom_major, i));
    class_destroy(srom_class);
fail_cdev:
    cdev_del(&srom_cdev);
fail_chrdev:
    unregister_chrdev_region(dev, srom_devs);
fail_mem:
    kfree(srom_devices);
    return result;
}

static void srom_cleanup(void)
{
    int i;
    for (i = 0; i < srom_devs; i++)
        device_destroy(srom_class, MKDEV(srom_major, i));
    class_destroy(srom_class);
    cdev_del(&srom_cdev);
    unregister_chrdev_region(MKDEV(srom_major, 0), srom_devs);
    kfree(srom_devices);
}

module_init(srom_init);
module_exit(srom_cleanup);