host.c

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/*
 *  linux/drivers/mmc/core/host.c
 *
 *  Copyright (C) 2003 Russell King, All Rights Reserved.
 *  Copyright (C) 2007-2008 Pierre Ossman
 *  Copyright (C) 2010 Linus Walleij
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  MMC host class device management
 */

#include <linux/device.h>
#include <linux/err.h>
#include <linux/idr.h>
#include <linux/pagemap.h>
#include <linux/export.h>
#include <linux/leds.h>
#include <linux/slab.h>
#include <linux/suspend.h>

#include <linux/mmc/host.h>
#include <linux/mmc/card.h>

#include "core.h"
#include "host.h"

#define cls_dev_to_mmc_host(d)  container_of(d, struct mmc_host, class_dev)

static void mmc_host_classdev_release(struct device *dev)
{
    struct mmc_host *host = cls_dev_to_mmc_host(dev);
    mutex_destroy(&host->slot.lock);
    kfree(host);
}

static struct class mmc_host_class = {
    .name       = "mmc_host",
    .dev_release    = mmc_host_classdev_release,
};

int mmc_register_host_class(void)
{
    return class_register(&mmc_host_class);
}

void mmc_unregister_host_class(void)
{
    class_unregister(&mmc_host_class);
}

static DEFINE_IDR(mmc_host_idr);
static DEFINE_SPINLOCK(mmc_host_lock);

#ifdef CONFIG_MMC_CLKGATE
static ssize_t clkgate_delay_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct mmc_host *host = cls_dev_to_mmc_host(dev);
    return snprintf(buf, PAGE_SIZE, "%lu\n", host->clkgate_delay);
}

static ssize_t clkgate_delay_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t count)
{
    struct mmc_host *host = cls_dev_to_mmc_host(dev);
    unsigned long flags, value;

    if (kstrtoul(buf, 0, &value))
        return -EINVAL;

    spin_lock_irqsave(&host->clk_lock, flags);
    host->clkgate_delay = value;
    spin_unlock_irqrestore(&host->clk_lock, flags);
    return count;
}

/*
 * Enabling clock gating will make the core call out to the host
 * once up and once down when it performs a request or card operation
 * intermingled in any fashion. The driver will see this through
 * set_ios() operations with ios.clock field set to 0 to gate (disable)
 * the block clock, and to the old frequency to enable it again.
 */
static void mmc_host_clk_gate_delayed(struct mmc_host *host)
{
    unsigned long tick_ns;
    unsigned long freq = host->ios.clock;
    unsigned long flags;

    if (!freq) {
        pr_debug("%s: frequency set to 0 in disable function, "
             "this means the clock is already disabled.\n",
             mmc_hostname(host));
        return;
    }
    /*
     * New requests may have appeared while we were scheduling,
     * then there is no reason to delay the check before
     * clk_disable().
     */
    spin_lock_irqsave(&host->clk_lock, flags);

    /*
     * Delay n bus cycles (at least 8 from MMC spec) before attempting
     * to disable the MCI block clock. The reference count may have
     * gone up again after this delay due to rescheduling!
     */
    if (!host->clk_requests) {
        spin_unlock_irqrestore(&host->clk_lock, flags);
        tick_ns = DIV_ROUND_UP(1000000000, freq);
        ndelay(host->clk_delay * tick_ns);
    } else {
        /* New users appeared while waiting for this work */
        spin_unlock_irqrestore(&host->clk_lock, flags);
        return;
    }
    mutex_lock(&host->clk_gate_mutex);
    spin_lock_irqsave(&host->clk_lock, flags);
    if (!host->clk_requests) {
        spin_unlock_irqrestore(&host->clk_lock, flags);
        /* This will set host->ios.clock to 0 */
        mmc_gate_clock(host);
        spin_lock_irqsave(&host->clk_lock, flags);
        pr_debug("%s: gated MCI clock\n", mmc_hostname(host));
    }
    spin_unlock_irqrestore(&host->clk_lock, flags);
    mutex_unlock(&host->clk_gate_mutex);
}

/*
 * Internal work. Work to disable the clock at some later point.
 */
static void mmc_host_clk_gate_work(struct work_struct *work)
{
    struct mmc_host *host = container_of(work, struct mmc_host,
                          clk_gate_work.work);

    mmc_host_clk_gate_delayed(host);
}

void mmc_host_clk_hold(struct mmc_host *host)
{
    unsigned long flags;

    /* cancel any clock gating work scheduled by mmc_host_clk_release() */
    cancel_delayed_work_sync(&host->clk_gate_work);
    mutex_lock(&host->clk_gate_mutex);
    spin_lock_irqsave(&host->clk_lock, flags);
    if (host->clk_gated) {
        spin_unlock_irqrestore(&host->clk_lock, flags);
        mmc_ungate_clock(host);
        spin_lock_irqsave(&host->clk_lock, flags);
        pr_debug("%s: ungated MCI clock\n", mmc_hostname(host));
    }
    host->clk_requests++;
    spin_unlock_irqrestore(&host->clk_lock, flags);
    mutex_unlock(&host->clk_gate_mutex);
}

static bool mmc_host_may_gate_card(struct mmc_card *card)
{
    /* If there is no card we may gate it */
    if (!card)
        return true;
    /*
     * Don't gate SDIO cards! These need to be clocked at all times
     * since they may be independent systems generating interrupts
     * and other events. The clock requests counter from the core will
     * go down to zero since the core does not need it, but we will not
     * gate the clock, because there is somebody out there that may still
     * be using it.
     */
    return !(card->quirks & MMC_QUIRK_BROKEN_CLK_GATING);
}

void mmc_host_clk_release(struct mmc_host *host)
{
    unsigned long flags;

    spin_lock_irqsave(&host->clk_lock, flags);
    host->clk_requests--;
    if (mmc_host_may_gate_card(host->card) &&
        !host->clk_requests)
        schedule_delayed_work(&host->clk_gate_work,
                      msecs_to_jiffies(host->clkgate_delay));
    spin_unlock_irqrestore(&host->clk_lock, flags);
}

unsigned int mmc_host_clk_rate(struct mmc_host *host)
{
    unsigned long freq;
    unsigned long flags;

    spin_lock_irqsave(&host->clk_lock, flags);
    if (host->clk_gated)
        freq = host->clk_old;
    else
        freq = host->ios.clock;
    spin_unlock_irqrestore(&host->clk_lock, flags);
    return freq;
}

static inline void mmc_host_clk_init(struct mmc_host *host)
{
    host->clk_requests = 0;
    /* Hold MCI clock for 8 cycles by default */
    host->clk_delay = 8;
    /*
     * Default clock gating delay is 0ms to avoid wasting power.
     * This value can be tuned by writing into sysfs entry.
     */
    host->clkgate_delay = 0;
    host->clk_gated = false;
    INIT_DELAYED_WORK(&host->clk_gate_work, mmc_host_clk_gate_work);
    spin_lock_init(&host->clk_lock);
    mutex_init(&host->clk_gate_mutex);
}

static inline void mmc_host_clk_exit(struct mmc_host *host)
{
    /*
     * Wait for any outstanding gate and then make sure we're
     * ungated before exiting.
     */
    if (cancel_delayed_work_sync(&host->clk_gate_work))
        mmc_host_clk_gate_delayed(host);
    if (host->clk_gated)
        mmc_host_clk_hold(host);
    /* There should be only one user now */
    WARN_ON(host->clk_requests > 1);
}

static inline void mmc_host_clk_sysfs_init(struct mmc_host *host)
{
    host->clkgate_delay_attr.show = clkgate_delay_show;
    host->clkgate_delay_attr.store = clkgate_delay_store;
    sysfs_attr_init(&host->clkgate_delay_attr.attr);
    host->clkgate_delay_attr.attr.name = "clkgate_delay";
    host->clkgate_delay_attr.attr.mode = S_IRUGO | S_IWUSR;
    if (device_create_file(&host->class_dev, &host->clkgate_delay_attr))
        pr_err("%s: Failed to create clkgate_delay sysfs entry\n",
                mmc_hostname(host));
}
#else

static inline void mmc_host_clk_init(struct mmc_host *host)
{
}

static inline void mmc_host_clk_exit(struct mmc_host *host)
{
}

static inline void mmc_host_clk_sysfs_init(struct mmc_host *host)
{
}

#endif

struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
{
    int err;
    struct mmc_host *host;

    if (!idr_pre_get(&mmc_host_idr, GFP_KERNEL))
        return NULL;

    host = kzalloc(sizeof(struct mmc_host) + extra, GFP_KERNEL);
    if (!host)
        return NULL;

    /* scanning will be enabled when we're ready */
    host->rescan_disable = 1;
    spin_lock(&mmc_host_lock);
    err = idr_get_new(&mmc_host_idr, host, &host->index);
    spin_unlock(&mmc_host_lock);
    if (err)
        goto free;

    dev_set_name(&host->class_dev, "mmc%d", host->index);

    host->parent = dev;
    host->class_dev.parent = dev;
    host->class_dev.class = &mmc_host_class;
    device_initialize(&host->class_dev);

    mmc_host_clk_init(host);

    mutex_init(&host->slot.lock);
    host->slot.cd_irq = -EINVAL;

    spin_lock_init(&host->lock);
    init_waitqueue_head(&host->wq);
    INIT_DELAYED_WORK(&host->detect, mmc_rescan);
#ifdef CONFIG_PM
    host->pm_notify.notifier_call = mmc_pm_notify;
#endif

    /*
     * By default, hosts do not support SGIO or large requests.
     * They have to set these according to their abilities.
     */
    host->max_segs = 1;
    host->max_seg_size = PAGE_CACHE_SIZE;

    host->max_req_size = PAGE_CACHE_SIZE;
    host->max_blk_size = 512;
    host->max_blk_count = PAGE_CACHE_SIZE / 512;

    return host;

free:
    kfree(host);
    return NULL;
}

EXPORT_SYMBOL(mmc_alloc_host);

int mmc_add_host(struct mmc_host *host)
{
    int err;

    WARN_ON((host->caps & MMC_CAP_SDIO_IRQ) &&
        !host->ops->enable_sdio_irq);

    err = device_add(&host->class_dev);
    if (err)
        return err;

    led_trigger_register_simple(dev_name(&host->class_dev), &host->led);

#ifdef CONFIG_DEBUG_FS
    mmc_add_host_debugfs(host);
#endif
    mmc_host_clk_sysfs_init(host);

    mmc_start_host(host);
    register_pm_notifier(&host->pm_notify);

    return 0;
}

EXPORT_SYMBOL(mmc_add_host);

void mmc_remove_host(struct mmc_host *host)
{
    unregister_pm_notifier(&host->pm_notify);
    mmc_stop_host(host);

#ifdef CONFIG_DEBUG_FS
    mmc_remove_host_debugfs(host);
#endif

    device_del(&host->class_dev);

    led_trigger_unregister_simple(host->led);

    mmc_host_clk_exit(host);
}

EXPORT_SYMBOL(mmc_remove_host);

void mmc_free_host(struct mmc_host *host)
{
    spin_lock(&mmc_host_lock);
    idr_remove(&mmc_host_idr, host->index);
    spin_unlock(&mmc_host_lock);

    put_device(&host->class_dev);
}

EXPORT_SYMBOL(mmc_free_host);