olpc-ec.c

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/*
 * Generic driver for the OLPC Embedded Controller.
 *
 * Copyright (C) 2011-2012 One Laptop per Child Foundation.
 *
 * Licensed under the GPL v2 or later.
 */
#include <linux/completion.h>
#include <linux/debugfs.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/olpc-ec.h>
#include <asm/olpc.h>

struct ec_cmd_desc {
    u8 cmd;
    u8 *inbuf, *outbuf;
    size_t inlen, outlen;

    int err;
    struct completion finished;
    struct list_head node;

    void *priv;
};

struct olpc_ec_priv {
    struct olpc_ec_driver *drv;
    struct work_struct worker;
    struct mutex cmd_lock;

    /* Pending EC commands */
    struct list_head cmd_q;
    spinlock_t cmd_q_lock;

    struct dentry *dbgfs_dir;

    /*
     * Running an EC command while suspending means we don't always finish
     * the command before the machine suspends.  This means that the EC
     * is expecting the command protocol to finish, but we after a period
     * of time (while the OS is asleep) the EC times out and restarts its
     * idle loop.  Meanwhile, the OS wakes up, thinks it's still in the
     * middle of the command protocol, starts throwing random things at
     * the EC... and everyone's uphappy.
     */
    bool suspended;
};

static struct olpc_ec_driver *ec_driver;
static struct olpc_ec_priv *ec_priv;
static void *ec_cb_arg;

void olpc_ec_driver_register(struct olpc_ec_driver *drv, void *arg)
{
    ec_driver = drv;
    ec_cb_arg = arg;
}
EXPORT_SYMBOL_GPL(olpc_ec_driver_register);

static void olpc_ec_worker(struct work_struct *w)
{
    struct olpc_ec_priv *ec = container_of(w, struct olpc_ec_priv, worker);
    struct ec_cmd_desc *desc = NULL;
    unsigned long flags;

    /* Grab the first pending command from the queue */
    spin_lock_irqsave(&ec->cmd_q_lock, flags);
    if (!list_empty(&ec->cmd_q)) {
        desc = list_first_entry(&ec->cmd_q, struct ec_cmd_desc, node);
        list_del(&desc->node);
    }
    spin_unlock_irqrestore(&ec->cmd_q_lock, flags);

    /* Do we actually have anything to do? */
    if (!desc)
        return;

    /* Protect the EC hw with a mutex; only run one cmd at a time */
    mutex_lock(&ec->cmd_lock);
    desc->err = ec_driver->ec_cmd(desc->cmd, desc->inbuf, desc->inlen,
            desc->outbuf, desc->outlen, ec_cb_arg);
    mutex_unlock(&ec->cmd_lock);

    /* Finished, wake up olpc_ec_cmd() */
    complete(&desc->finished);

    /* Run the worker thread again in case there are more cmds pending */
    schedule_work(&ec->worker);
}

/*
 * Throw a cmd descripter onto the list.  We now have SMP OLPC machines, so
 * locking is pretty critical.
 */
static void queue_ec_descriptor(struct ec_cmd_desc *desc,
        struct olpc_ec_priv *ec)
{
    unsigned long flags;

    INIT_LIST_HEAD(&desc->node);

    spin_lock_irqsave(&ec->cmd_q_lock, flags);
    list_add_tail(&desc->node, &ec->cmd_q);
    spin_unlock_irqrestore(&ec->cmd_q_lock, flags);

    schedule_work(&ec->worker);
}

int olpc_ec_cmd(u8 cmd, u8 *inbuf, size_t inlen, u8 *outbuf, size_t outlen)
{
    struct olpc_ec_priv *ec = ec_priv;
    struct ec_cmd_desc desc;

    /* Ensure a driver and ec hook have been registered */
    if (WARN_ON(!ec_driver || !ec_driver->ec_cmd))
        return -ENODEV;

    if (!ec)
        return -ENOMEM;

    /* Suspending in the middle of a command hoses things really badly */
    if (WARN_ON(ec->suspended))
        return -EBUSY;

    might_sleep();

    desc.cmd = cmd;
    desc.inbuf = inbuf;
    desc.outbuf = outbuf;
    desc.inlen = inlen;
    desc.outlen = outlen;
    desc.err = 0;
    init_completion(&desc.finished);

    queue_ec_descriptor(&desc, ec);

    /* Timeouts must be handled in the platform-specific EC hook */
    wait_for_completion(&desc.finished);

    /* The worker thread dequeues the cmd; no need to do anything here */
    return desc.err;
}
EXPORT_SYMBOL_GPL(olpc_ec_cmd);

#ifdef CONFIG_DEBUG_FS

/*
 * debugfs support for "generic commands", to allow sending
 * arbitrary EC commands from userspace.
 */

#define EC_MAX_CMD_ARGS (5 + 1)     /* cmd byte + 5 args */
#define EC_MAX_CMD_REPLY (8)

static DEFINE_MUTEX(ec_dbgfs_lock);
static unsigned char ec_dbgfs_resp[EC_MAX_CMD_REPLY];
static unsigned int ec_dbgfs_resp_bytes;

static ssize_t ec_dbgfs_cmd_write(struct file *file, const char __user *buf,
        size_t size, loff_t *ppos)
{
    int i, m;
    unsigned char ec_cmd[EC_MAX_CMD_ARGS];
    unsigned int ec_cmd_int[EC_MAX_CMD_ARGS];
    char cmdbuf[64];
    int ec_cmd_bytes;

    mutex_lock(&ec_dbgfs_lock);

    size = simple_write_to_buffer(cmdbuf, sizeof(cmdbuf), ppos, buf, size);

    m = sscanf(cmdbuf, "%x:%u %x %x %x %x %x", &ec_cmd_int[0],
            &ec_dbgfs_resp_bytes, &ec_cmd_int[1], &ec_cmd_int[2],
            &ec_cmd_int[3], &ec_cmd_int[4], &ec_cmd_int[5]);
    if (m < 2 || ec_dbgfs_resp_bytes > EC_MAX_CMD_REPLY) {
        /* reset to prevent overflow on read */
        ec_dbgfs_resp_bytes = 0;

        pr_debug("olpc-ec: bad ec cmd:  cmd:response-count [arg1 [arg2 ...]]\n");
        size = -EINVAL;
        goto out;
    }

    /* convert scanf'd ints to char */
    ec_cmd_bytes = m - 2;
    for (i = 0; i <= ec_cmd_bytes; i++)
        ec_cmd[i] = ec_cmd_int[i];

    pr_debug("olpc-ec: debugfs cmd 0x%02x with %d args %02x %02x %02x %02x %02x, want %d returns\n",
            ec_cmd[0], ec_cmd_bytes, ec_cmd[1], ec_cmd[2],
            ec_cmd[3], ec_cmd[4], ec_cmd[5], ec_dbgfs_resp_bytes);

    olpc_ec_cmd(ec_cmd[0], (ec_cmd_bytes == 0) ? NULL : &ec_cmd[1],
            ec_cmd_bytes, ec_dbgfs_resp, ec_dbgfs_resp_bytes);

    pr_debug("olpc-ec: response %02x %02x %02x %02x %02x %02x %02x %02x (%d bytes expected)\n",
            ec_dbgfs_resp[0], ec_dbgfs_resp[1], ec_dbgfs_resp[2],
            ec_dbgfs_resp[3], ec_dbgfs_resp[4], ec_dbgfs_resp[5],
            ec_dbgfs_resp[6], ec_dbgfs_resp[7],
            ec_dbgfs_resp_bytes);

out:
    mutex_unlock(&ec_dbgfs_lock);
    return size;
}

static ssize_t ec_dbgfs_cmd_read(struct file *file, char __user *buf,
        size_t size, loff_t *ppos)
{
    unsigned int i, r;
    char *rp;
    char respbuf[64];

    mutex_lock(&ec_dbgfs_lock);
    rp = respbuf;
    rp += sprintf(rp, "%02x", ec_dbgfs_resp[0]);
    for (i = 1; i < ec_dbgfs_resp_bytes; i++)
        rp += sprintf(rp, ", %02x", ec_dbgfs_resp[i]);
    mutex_unlock(&ec_dbgfs_lock);
    rp += sprintf(rp, "\n");

    r = rp - respbuf;
    return simple_read_from_buffer(buf, size, ppos, respbuf, r);
}

static const struct file_operations ec_dbgfs_ops = {
    .write = ec_dbgfs_cmd_write,
    .read = ec_dbgfs_cmd_read,
};

static struct dentry *olpc_ec_setup_debugfs(void)
{
    struct dentry *dbgfs_dir;

    dbgfs_dir = debugfs_create_dir("olpc-ec", NULL);
    if (IS_ERR_OR_NULL(dbgfs_dir))
        return NULL;

    debugfs_create_file("cmd", 0600, dbgfs_dir, NULL, &ec_dbgfs_ops);

    return dbgfs_dir;
}

#else

static struct dentry *olpc_ec_setup_debugfs(void)
{
    return NULL;
}

#endif /* CONFIG_DEBUG_FS */

static int olpc_ec_probe(struct platform_device *pdev)
{
    struct olpc_ec_priv *ec;
    int err;

    if (!ec_driver)
        return -ENODEV;

    ec = kzalloc(sizeof(*ec), GFP_KERNEL);
    if (!ec)
        return -ENOMEM;

    ec->drv = ec_driver;
    INIT_WORK(&ec->worker, olpc_ec_worker);
    mutex_init(&ec->cmd_lock);

    INIT_LIST_HEAD(&ec->cmd_q);
    spin_lock_init(&ec->cmd_q_lock);

    ec_priv = ec;
    platform_set_drvdata(pdev, ec);

    err = ec_driver->probe ? ec_driver->probe(pdev) : 0;
    if (err) {
        ec_priv = NULL;
        kfree(ec);
    } else {
        ec->dbgfs_dir = olpc_ec_setup_debugfs();
    }

    return err;
}

static int olpc_ec_suspend(struct device *dev)
{
    struct platform_device *pdev = to_platform_device(dev);
    struct olpc_ec_priv *ec = platform_get_drvdata(pdev);
    int err = 0;

    if (ec_driver->suspend)
        err = ec_driver->suspend(pdev);
    if (!err)
        ec->suspended = true;

    return err;
}

static int olpc_ec_resume(struct device *dev)
{
    struct platform_device *pdev = to_platform_device(dev);
    struct olpc_ec_priv *ec = platform_get_drvdata(pdev);

    ec->suspended = false;
    return ec_driver->resume ? ec_driver->resume(pdev) : 0;
}

static const struct dev_pm_ops olpc_ec_pm_ops = {
    .suspend_late = olpc_ec_suspend,
    .resume_early = olpc_ec_resume,
};

static struct platform_driver olpc_ec_plat_driver = {
    .probe = olpc_ec_probe,
    .driver = {
        .name = "olpc-ec",
        .pm = &olpc_ec_pm_ops,
    },
};

static int __init olpc_ec_init_module(void)
{
    return platform_driver_register(&olpc_ec_plat_driver);
}

module_init(olpc_ec_init_module);

MODULE_AUTHOR("Andres Salomon <[email protected]>");
MODULE_LICENSE("GPL");