x86 rwsem: avoid taking slow path when stealing write lock

[linux-2.6.git] / drivers / hsi / hsi.c

/*
 * HSI core.
 *
 * Copyright (C) 2010 Nokia Corporation. All rights reserved.
 *
 * Contact: Carlos Chinea <carlos.chinea@nokia.com>
 *
 * 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.
 *
 * 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., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */
#include <linux/hsi/hsi.h>
#include <linux/compiler.h>
#include <linux/list.h>
#include <linux/kobject.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/notifier.h>
#include "hsi_core.h"

static ssize_t modalias_show(struct device *dev,
                        struct device_attribute *a __maybe_unused, char *buf)
{
        return sprintf(buf, "hsi:%s\n", dev_name(dev));
}

static struct device_attribute hsi_bus_dev_attrs[] = {
        __ATTR_RO(modalias),
        __ATTR_NULL,
};

static int hsi_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
{
        add_uevent_var(env, "MODALIAS=hsi:%s", dev_name(dev));

        return 0;
}

static int hsi_bus_match(struct device *dev, struct device_driver *driver)
{
        return strcmp(dev_name(dev), driver->name) == 0;
}

static struct bus_type hsi_bus_type = {
        .name           = "hsi",
        .dev_attrs      = hsi_bus_dev_attrs,
        .match          = hsi_bus_match,
        .uevent         = hsi_bus_uevent,
};

static void hsi_client_release(struct device *dev)
{
        kfree(to_hsi_client(dev));
}

static void hsi_new_client(struct hsi_port *port, struct hsi_board_info *info)
{
        struct hsi_client *cl;

        cl = kzalloc(sizeof(*cl), GFP_KERNEL);
        if (!cl)
                return;
        cl->tx_cfg = info->tx_cfg;
        cl->rx_cfg = info->rx_cfg;
        cl->device.bus = &hsi_bus_type;
        cl->device.parent = &port->device;
        cl->device.release = hsi_client_release;
        dev_set_name(&cl->device, info->name);
        cl->device.platform_data = info->platform_data;
        if (info->archdata)
                cl->device.archdata = *info->archdata;
        if (device_register(&cl->device) < 0) {
                pr_err("hsi: failed to register client: %s\n", info->name);
                put_device(&cl->device);
        }
}

static void hsi_scan_board_info(struct hsi_controller *hsi)
{
        struct hsi_cl_info *cl_info;
        struct hsi_port *p;

        list_for_each_entry(cl_info, &hsi_board_list, list)
                if (cl_info->info.hsi_id == hsi->id) {
                        p = hsi_find_port_num(hsi, cl_info->info.port);
                        if (!p)
                                continue;
                        hsi_new_client(p, &cl_info->info);
                }
}

static int hsi_remove_client(struct device *dev, void *data __maybe_unused)
{
        device_unregister(dev);

        return 0;
}

static int hsi_remove_port(struct device *dev, void *data __maybe_unused)
{
        device_for_each_child(dev, NULL, hsi_remove_client);
        device_unregister(dev);

        return 0;
}

static void hsi_controller_release(struct device *dev)
{
        struct hsi_controller *hsi = to_hsi_controller(dev);

        kfree(hsi->port);
        kfree(hsi);
}

static void hsi_port_release(struct device *dev)
{
        kfree(to_hsi_port(dev));
}

/**
 * hsi_unregister_controller - Unregister an HSI controller
 * @hsi: The HSI controller to register
 */
void hsi_unregister_controller(struct hsi_controller *hsi)
{
        device_for_each_child(&hsi->device, NULL, hsi_remove_port);
        device_unregister(&hsi->device);
}
EXPORT_SYMBOL_GPL(hsi_unregister_controller);

/**
 * hsi_register_controller - Register an HSI controller and its ports
 * @hsi: The HSI controller to register
 *
 * Returns -errno on failure, 0 on success.
 */
int hsi_register_controller(struct hsi_controller *hsi)
{
        unsigned int i;
        int err;

        err = device_add(&hsi->device);
        if (err < 0)
                return err;
        for (i = 0; i < hsi->num_ports; i++) {
                hsi->port[i]->device.parent = &hsi->device;
                err = device_add(&hsi->port[i]->device);
                if (err < 0)
                        goto out;
        }
        /* Populate HSI bus with HSI clients */
        hsi_scan_board_info(hsi);

        return 0;
out:
        while (i-- > 0)
                device_del(&hsi->port[i]->device);
        device_del(&hsi->device);

        return err;
}
EXPORT_SYMBOL_GPL(hsi_register_controller);

/**
 * hsi_register_client_driver - Register an HSI client to the HSI bus
 * @drv: HSI client driver to register
 *
 * Returns -errno on failure, 0 on success.
 */
int hsi_register_client_driver(struct hsi_client_driver *drv)
{
        drv->driver.bus = &hsi_bus_type;

        return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(hsi_register_client_driver);

static inline int hsi_dummy_msg(struct hsi_msg *msg __maybe_unused)
{
        return 0;
}

static inline int hsi_dummy_cl(struct hsi_client *cl __maybe_unused)
{
        return 0;
}

/**
 * hsi_put_controller - Free an HSI controller
 *
 * @hsi: Pointer to the HSI controller to freed
 *
 * HSI controller drivers should only use this function if they need
 * to free their allocated hsi_controller structures before a successful
 * call to hsi_register_controller. Other use is not allowed.
 */
void hsi_put_controller(struct hsi_controller *hsi)
{
        unsigned int i;

        if (!hsi)
                return;

        for (i = 0; i < hsi->num_ports; i++)
                if (hsi->port && hsi->port[i])
                        put_device(&hsi->port[i]->device);
        put_device(&hsi->device);
}
EXPORT_SYMBOL_GPL(hsi_put_controller);

/**
 * hsi_alloc_controller - Allocate an HSI controller and its ports
 * @n_ports: Number of ports on the HSI controller
 * @flags: Kernel allocation flags
 *
 * Return NULL on failure or a pointer to an hsi_controller on success.
 */
struct hsi_controller *hsi_alloc_controller(unsigned int n_ports, gfp_t flags)
{
        struct hsi_controller   *hsi;
        struct hsi_port         **port;
        unsigned int            i;

        if (!n_ports)
                return NULL;

        hsi = kzalloc(sizeof(*hsi), flags);
        if (!hsi)
                return NULL;
        port = kzalloc(sizeof(*port)*n_ports, flags);
        if (!port) {
                kfree(hsi);
                return NULL;
        }
        hsi->num_ports = n_ports;
        hsi->port = port;
        hsi->device.release = hsi_controller_release;
        device_initialize(&hsi->device);

        for (i = 0; i < n_ports; i++) {
                port[i] = kzalloc(sizeof(**port), flags);
                if (port[i] == NULL)
                        goto out;
                port[i]->num = i;
                port[i]->async = hsi_dummy_msg;
                port[i]->setup = hsi_dummy_cl;
                port[i]->flush = hsi_dummy_cl;
                port[i]->start_tx = hsi_dummy_cl;
                port[i]->stop_tx = hsi_dummy_cl;
                port[i]->release = hsi_dummy_cl;
                mutex_init(&port[i]->lock);
                ATOMIC_INIT_NOTIFIER_HEAD(&port[i]->n_head);
                dev_set_name(&port[i]->device, "port%d", i);
                hsi->port[i]->device.release = hsi_port_release;
                device_initialize(&hsi->port[i]->device);
        }

        return hsi;
out:
        hsi_put_controller(hsi);

        return NULL;
}
EXPORT_SYMBOL_GPL(hsi_alloc_controller);

/**
 * hsi_free_msg - Free an HSI message
 * @msg: Pointer to the HSI message
 *
 * Client is responsible to free the buffers pointed by the scatterlists.
 */
void hsi_free_msg(struct hsi_msg *msg)
{
        if (!msg)
                return;
        sg_free_table(&msg->sgt);
        kfree(msg);
}
EXPORT_SYMBOL_GPL(hsi_free_msg);

/**
 * hsi_alloc_msg - Allocate an HSI message
 * @nents: Number of memory entries
 * @flags: Kernel allocation flags
 *
 * nents can be 0. This mainly makes sense for read transfer.
 * In that case, HSI drivers will call the complete callback when
 * there is data to be read without consuming it.
 *
 * Return NULL on failure or a pointer to an hsi_msg on success.
 */
struct hsi_msg *hsi_alloc_msg(unsigned int nents, gfp_t flags)
{
        struct hsi_msg *msg;
        int err;

        msg = kzalloc(sizeof(*msg), flags);
        if (!msg)
                return NULL;

        if (!nents)
                return msg;

        err = sg_alloc_table(&msg->sgt, nents, flags);
        if (unlikely(err)) {
                kfree(msg);
                msg = NULL;
        }

        return msg;
}
EXPORT_SYMBOL_GPL(hsi_alloc_msg);

/**
 * hsi_async - Submit an HSI transfer to the controller
 * @cl: HSI client sending the transfer
 * @msg: The HSI transfer passed to controller
 *
 * The HSI message must have the channel, ttype, complete and destructor
 * fields set beforehand. If nents > 0 then the client has to initialize
 * also the scatterlists to point to the buffers to write to or read from.
 *
 * HSI controllers relay on pre-allocated buffers from their clients and they
 * do not allocate buffers on their own.
 *
 * Once the HSI message transfer finishes, the HSI controller calls the
 * complete callback with the status and actual_len fields of the HSI message
 * updated. The complete callback can be called before returning from
 * hsi_async.
 *
 * Returns -errno on failure or 0 on success
 */
int hsi_async(struct hsi_client *cl, struct hsi_msg *msg)
{
        struct hsi_port *port = hsi_get_port(cl);

        if (!hsi_port_claimed(cl))
                return -EACCES;

        WARN_ON_ONCE(!msg->destructor || !msg->complete);
        msg->cl = cl;

        return port->async(msg);
}
EXPORT_SYMBOL_GPL(hsi_async);

/**
 * hsi_claim_port - Claim the HSI client's port
 * @cl: HSI client that wants to claim its port
 * @share: Flag to indicate if the client wants to share the port or not.
 *
 * Returns -errno on failure, 0 on success.
 */
int hsi_claim_port(struct hsi_client *cl, unsigned int share)
{
        struct hsi_port *port = hsi_get_port(cl);
        int err = 0;

        mutex_lock(&port->lock);
        if ((port->claimed) && (!port->shared || !share)) {
                err = -EBUSY;
                goto out;
        }
        if (!try_module_get(to_hsi_controller(port->device.parent)->owner)) {
                err = -ENODEV;
                goto out;
        }
        port->claimed++;
        port->shared = !!share;
        cl->pclaimed = 1;
out:
        mutex_unlock(&port->lock);

        return err;
}
EXPORT_SYMBOL_GPL(hsi_claim_port);

/**
 * hsi_release_port - Release the HSI client's port
 * @cl: HSI client which previously claimed its port
 */
void hsi_release_port(struct hsi_client *cl)
{
        struct hsi_port *port = hsi_get_port(cl);

        mutex_lock(&port->lock);
        /* Allow HW driver to do some cleanup */
        port->release(cl);
        if (cl->pclaimed)
                port->claimed--;
        BUG_ON(port->claimed < 0);
        cl->pclaimed = 0;
        if (!port->claimed)
                port->shared = 0;
        module_put(to_hsi_controller(port->device.parent)->owner);
        mutex_unlock(&port->lock);
}
EXPORT_SYMBOL_GPL(hsi_release_port);

static int hsi_event_notifier_call(struct notifier_block *nb,
                                unsigned long event, void *data __maybe_unused)
{
        struct hsi_client *cl = container_of(nb, struct hsi_client, nb);

        (*cl->ehandler)(cl, event);

        return 0;
}

/**
 * hsi_register_port_event - Register a client to receive port events
 * @cl: HSI client that wants to receive port events
 * @handler: Event handler callback
 *
 * Clients should register a callback to be able to receive
 * events from the ports. Registration should happen after
 * claiming the port.
 * The handler can be called in interrupt context.
 *
 * Returns -errno on error, or 0 on success.
 */
int hsi_register_port_event(struct hsi_client *cl,
                        void (*handler)(struct hsi_client *, unsigned long))
{
        struct hsi_port *port = hsi_get_port(cl);

        if (!handler || cl->ehandler)
                return -EINVAL;
        if (!hsi_port_claimed(cl))
                return -EACCES;
        cl->ehandler = handler;
        cl->nb.notifier_call = hsi_event_notifier_call;

        return atomic_notifier_chain_register(&port->n_head, &cl->nb);
}
EXPORT_SYMBOL_GPL(hsi_register_port_event);

/**
 * hsi_unregister_port_event - Stop receiving port events for a client
 * @cl: HSI client that wants to stop receiving port events
 *
 * Clients should call this function before releasing their associated
 * port.
 *
 * Returns -errno on error, or 0 on success.
 */
int hsi_unregister_port_event(struct hsi_client *cl)
{
        struct hsi_port *port = hsi_get_port(cl);
        int err;

        WARN_ON(!hsi_port_claimed(cl));

        err = atomic_notifier_chain_unregister(&port->n_head, &cl->nb);
        if (!err)
                cl->ehandler = NULL;

        return err;
}
EXPORT_SYMBOL_GPL(hsi_unregister_port_event);

/**
 * hsi_event -Notifies clients about port events
 * @port: Port where the event occurred
 * @event: The event type
 *
 * Clients should not be concerned about wake line behavior. However, due
 * to a race condition in HSI HW protocol, clients need to be notified
 * about wake line changes, so they can implement a workaround for it.
 *
 * Events:
 * HSI_EVENT_START_RX - Incoming wake line high
 * HSI_EVENT_STOP_RX - Incoming wake line down
 *
 * Returns -errno on error, or 0 on success.
 */
int hsi_event(struct hsi_port *port, unsigned long event)
{
        return atomic_notifier_call_chain(&port->n_head, event, NULL);
}
EXPORT_SYMBOL_GPL(hsi_event);

static int __init hsi_init(void)
{
        return bus_register(&hsi_bus_type);
}
postcore_initcall(hsi_init);

static void __exit hsi_exit(void)
{
        bus_unregister(&hsi_bus_type);
}
module_exit(hsi_exit);

MODULE_AUTHOR("Carlos Chinea <carlos.chinea@nokia.com>");
MODULE_DESCRIPTION("High-speed Synchronous Serial Interface (HSI) framework");
MODULE_LICENSE("GPL v2");