/*
 * Intel Wireless WiMAX Connection 2400m
 * USB-specific i2400m driver definitions
 *
 *
 * Copyright (C) 2007-2008 Intel Corporation. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in
 *     the documentation and/or other materials provided with the
 *     distribution.
 *   * Neither the name of Intel Corporation nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * Intel Corporation <linux-wimax@intel.com>
 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
 * Yanir Lubetkin <yanirx.lubetkin@intel.com>
 *  - Initial implementation
 *
 *
 * This driver implements the bus-specific part of the i2400m for
 * USB. Check i2400m.h for a generic driver description.
 *
 * ARCHITECTURE
 *
 * This driver listens to notifications sent from the notification
 * endpoint (in usb-notif.c); when data is ready to read, the code in
 * there schedules a read from the device (usb-rx.c) and then passes
 * the data to the generic RX code (rx.c).
 *
 * When the generic driver needs to send data (network or control), it
 * queues up in the TX FIFO (tx.c) and that will notify the driver
 * through the i2400m->bus_tx_kick() callback
 * (usb-tx.c:i2400mu_bus_tx_kick) which will send the items in the
 * FIFO queue.
 *
 * This driver, as well, implements the USB-specific ops for the generic
 * driver to be able to setup/teardown communication with the device
 * [i2400m_bus_dev_start() and i2400m_bus_dev_stop()], reseting the
 * device [i2400m_bus_reset()] and performing firmware upload
 * [i2400m_bus_bm_cmd() and i2400_bus_bm_wait_for_ack()].
 */

#ifndef __I2400M_USB_H__
#define __I2400M_USB_H__

#include "i2400m.h"
#include <linux/kthread.h>


/*
 * Error Density Count: cheapo error density (over time) counter
 *
 * Originally by Reinette Chatre <reinette.chatre@intel.com>
 *
 * Embed an 'struct edc' somewhere. Each time there is a soft or
 * retryable error, call edc_inc() and check if the error top
 * watermark has been reached.
 */
enum {
	EDC_MAX_ERRORS = 10,
	EDC_ERROR_TIMEFRAME = HZ,
};

/* error density counter */
struct edc {
	unsigned long timestart;
	u16 errorcount;
};

static inline void edc_init(struct edc *edc)
{
	edc->timestart = jiffies;
}

/**
 * edc_inc - report a soft error and check if we are over the watermark
 *
 * @edc: pointer to error density counter.
 * @max_err: maximum number of errors we can accept over the timeframe
 * @timeframe: lenght of the timeframe (in jiffies).
 *
 * Returns: !0 1 if maximum acceptable errors per timeframe has been
 *     exceeded. 0 otherwise.
 *
 * This is way to determine if the number of acceptable errors per time
 * period has been exceeded. It is not accurate as there are cases in which
 * this scheme will not work, for example if there are periodic occurences
 * of errors that straddle updates to the start time. This scheme is
 * sufficient for our usage.
 *
 * To use, embed a 'struct edc' somewhere, initialize it with
 * edc_init() and when an error hits:
 *
 * if (do_something_fails_with_a_soft_error) {
 *        if (edc_inc(&my->edc, MAX_ERRORS, MAX_TIMEFRAME))
 * 	           Ops, hard error, do something about it
 *        else
 *                 Retry or ignore, depending on whatever
 * }
 */
static inline int edc_inc(struct edc *edc, u16 max_err, u16 timeframe)
{
	unsigned long now;

	now = jiffies;
	if (now - edc->timestart > timeframe) {
		edc->errorcount = 1;
		edc->timestart = now;
	} else if (++edc->errorcount > max_err) {
		edc->errorcount = 0;
		edc->timestart = now;
		return 1;
	}
	return 0;
}

/* Host-Device interface for USB */
enum {
	I2400MU_MAX_NOTIFICATION_LEN = 256,
	I2400MU_BLK_SIZE = 16,
	I2400MU_PL_SIZE_MAX = 0x3EFF,

	/* Endpoints */
	I2400MU_EP_BULK_OUT = 0,
	I2400MU_EP_NOTIFICATION,
	I2400MU_EP_RESET_COLD,
	I2400MU_EP_BULK_IN,
};


/**
 * struct i2400mu - descriptor for a USB connected i2400m
 *
 * @i2400m: bus-generic i2400m implementation; has to be first (see
 *     it's documentation in i2400m.h).
 *
 * @usb_dev: pointer to our USB device
 *
 * @usb_iface: pointer to our USB interface
 *
 * @urb_edc: error density counter; used to keep a density-on-time tab
 *     on how many soft (retryable or ignorable) errors we get. If we
 *     go over the threshold, we consider the bus transport is failing
 *     too much and reset.
 *
 * @notif_urb: URB for receiving notifications from the device.
 *
 * @tx_kthread: thread we use for data TX. We use a thread because in
 *     order to do deep power saving and put the device to sleep, we
 *     need to call usb_autopm_*() [blocking functions].
 *
 * @tx_wq: waitqueue for the TX kthread to sleep when there is no data
 *     to be sent; when more data is available, it is woken up by
 *     i2400mu_bus_tx_kick().
 *
 * @rx_kthread: thread we use for data RX. We use a thread because in
 *     order to do deep power saving and put the device to sleep, we
 *     need to call usb_autopm_*() [blocking functions].
 *
 * @rx_wq: waitqueue for the RX kthread to sleep when there is no data
 *     to receive. When data is available, it is woken up by
 *     usb-notif.c:i2400mu_notification_grok().
 *
 * @rx_pending_count: number of rx-data-ready notifications that were
 *     still not handled by the RX kthread.
 *
 * @rx_size: current RX buffer size that is being used.
 *
 * @rx_size_acc: accumulator of the sizes of the previous read
 *     transactions.
 *
 * @rx_size_cnt: number of read transactions accumulated in
 *     @rx_size_acc.
 *
 * @do_autopm: disable(0)/enable(>0) calling the
 *     usb_autopm_get/put_interface() barriers when executing
 *     commands. See doc in i2400mu_suspend() for more information.
 *
 * @rx_size_auto_shrink: if true, the rx_size is shrinked
 *     automatically based on the average size of the received
 *     transactions. This allows the receive code to allocate smaller
 *     chunks of memory and thus reduce pressure on the memory
 *     allocator by not wasting so much space. By default it is
 *     enabled.
 *
 * @debugfs_dentry: hookup for debugfs files.
 *     These have to be in a separate directory, a child of
 *     (wimax_dev->debugfs_dentry) so they can be removed when the
 *     module unloads, as we don't keep each dentry.
 */
struct i2400mu {
	struct i2400m i2400m;		/* FIRST! See doc */

	struct usb_device *usb_dev;
	struct usb_interface *usb_iface;
	struct edc urb_edc;		/* Error density counter */

	struct urb *notif_urb;
	struct task_struct *tx_kthread;
	wait_queue_head_t tx_wq;

	struct task_struct *rx_kthread;
	wait_queue_head_t rx_wq;
	atomic_t rx_pending_count;
	size_t rx_size, rx_size_acc, rx_size_cnt;
	atomic_t do_autopm;
	u8 rx_size_auto_shrink;

	struct dentry *debugfs_dentry;
};


static inline
void i2400mu_init(struct i2400mu *i2400mu)
{
	i2400m_init(&i2400mu->i2400m);
	edc_init(&i2400mu->urb_edc);
	init_waitqueue_head(&i2400mu->tx_wq);
	atomic_set(&i2400mu->rx_pending_count, 0);
	init_waitqueue_head(&i2400mu->rx_wq);
	i2400mu->rx_size = PAGE_SIZE - sizeof(struct skb_shared_info);
	atomic_set(&i2400mu->do_autopm, 1);
	i2400mu->rx_size_auto_shrink = 1;
}

extern int i2400mu_notification_setup(struct i2400mu *);
extern void i2400mu_notification_release(struct i2400mu *);

extern int i2400mu_rx_setup(struct i2400mu *);
extern void i2400mu_rx_release(struct i2400mu *);
extern void i2400mu_rx_kick(struct i2400mu *);

extern int i2400mu_tx_setup(struct i2400mu *);
extern void i2400mu_tx_release(struct i2400mu *);
extern void i2400mu_bus_tx_kick(struct i2400m *);

extern ssize_t i2400mu_bus_bm_cmd_send(struct i2400m *,
				       const struct i2400m_bootrom_header *,
				       size_t, int);
extern ssize_t i2400mu_bus_bm_wait_for_ack(struct i2400m *,
					   struct i2400m_bootrom_header *,
					   size_t);
#endif /* #ifndef __I2400M_USB_H__ */