/*
 * Intel Wireless WiMAX Connection 2400m
 * USB RX handling
 *
 *
 * 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>
 * Yanir Lubetkin <yanirx.lubetkin@intel.com>
 *  - Initial implementation
 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
 *  - Use skb_clone(), break up processing in chunks
 *  - Split transport/device specific
 *  - Make buffer size dynamic to exert less memory pressure
 *
 *
 * This handles the RX path on USB.
 *
 * When a notification is received that says 'there is RX data ready',
 * we call i2400mu_rx_kick(); that wakes up the RX kthread, which
 * reads a buffer from USB and passes it to i2400m_rx() in the generic
 * handling code. The RX buffer has an specific format that is
 * described in rx.c.
 *
 * We use a kernel thread in a loop because:
 *
 *  - we want to be able to call the USB power management get/put
 *    functions (blocking) before each transaction.
 *
 *  - We might get a lot of notifications and we don't want to submit
 *    a zillion reads; by serializing, we are throttling.
 *
 *  - RX data processing can get heavy enough so that it is not
 *    appropriate for doing it in the USB callback; thus we run it in a
 *    process context.
 *
 * We provide a read buffer of an arbitrary size (short of a page); if
 * the callback reports -EOVERFLOW, it means it was too small, so we
 * just double the size and retry (being careful to append, as
 * sometimes the device provided some data). Every now and then we
 * check if the average packet size is smaller than the current packet
 * size and if so, we halve it. At the end, the size of the
 * preallocated buffer should be following the average received
 * transaction size, adapting dynamically to it.
 *
 * ROADMAP
 *
 * i2400mu_rx_kick()               Called from notif.c when we get a
 *                                 'data ready' notification
 * i2400mu_rxd()                   Kernel RX daemon
 *   i2400mu_rx()                  Receive USB data
 *   i2400m_rx()                   Send data to generic i2400m RX handling
 *
 * i2400mu_rx_setup()              called from i2400mu_bus_dev_start()
 *
 * i2400mu_rx_release()            called from i2400mu_bus_dev_stop()
 */
#include <linux/workqueue.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include "i2400m-usb.h"


#define D_SUBMODULE rx
#include "usb-debug-levels.h"

/*
 * Dynamic RX size
 *
 * We can't let the rx_size be a multiple of 512 bytes (the RX
 * endpoint's max packet size). On some USB host controllers (we
 * haven't been able to fully characterize which), if the device is
 * about to send (for example) X bytes and we only post a buffer to
 * receive n*512, it will fail to mark that as babble (so that
 * i2400mu_rx() [case -EOVERFLOW] can resize the buffer and get the
 * rest).
 *
 * So on growing or shrinking, if it is a multiple of the
 * maxpacketsize, we remove some (instead of incresing some, so in a
 * buddy allocator we try to waste less space).
 *
 * Note we also need a hook for this on i2400mu_rx() -- when we do the
 * first read, we are sure we won't hit this spot because
 * i240mm->rx_size has been set properly. However, if we have to
 * double because of -EOVERFLOW, when we launch the read to get the
 * rest of the data, we *have* to make sure that also is not a
 * multiple of the max_pkt_size.
 */

static
size_t i2400mu_rx_size_grow(struct i2400mu *i2400mu)
{
        struct device *dev = &i2400mu->usb_iface->dev;
        size_t rx_size;
        const size_t max_pkt_size = 512;

        rx_size = 2 * i2400mu->rx_size;
        if (rx_size % max_pkt_size == 0) {
                rx_size -= 8;
                d_printf(1, dev,
                         "RX: expected size grew to %zu [adjusted -8] "
                         "from %zu\n",
                         rx_size, i2400mu->rx_size);
        } else
                d_printf(1, dev,
                         "RX: expected size grew to %zu from %zu\n",
                         rx_size, i2400mu->rx_size);
        return rx_size;
}


static
void i2400mu_rx_size_maybe_shrink(struct i2400mu *i2400mu)
{
        const size_t max_pkt_size = 512;
        struct device *dev = &i2400mu->usb_iface->dev;

        if (unlikely(i2400mu->rx_size_cnt >= 100
                     && i2400mu->rx_size_auto_shrink)) {
                size_t avg_rx_size =
                        i2400mu->rx_size_acc / i2400mu->rx_size_cnt;
                size_t new_rx_size = i2400mu->rx_size / 2;
                if (avg_rx_size < new_rx_size) {
                        if (new_rx_size % max_pkt_size == 0) {
                                new_rx_size -= 8;
                                d_printf(1, dev,
                                         "RX: expected size shrank to %zu "
                                         "[adjusted -8] from %zu\n",
                                         new_rx_size, i2400mu->rx_size);
                        } else
                                d_printf(1, dev,
                                         "RX: expected size shrank to %zu "
                                         "from %zu\n",
                                         new_rx_size, i2400mu->rx_size);
                        i2400mu->rx_size = new_rx_size;
                        i2400mu->rx_size_cnt = 0;
                        i2400mu->rx_size_acc = i2400mu->rx_size;
                }
        }
}

/*
 * Receive a message with payloads from the USB bus into an skb
 *
 * @i2400mu: USB device descriptor
 * @rx_skb: skb where to place the received message
 *
 * Deals with all the USB-specifics of receiving, dynamically
 * increasing the buffer size if so needed. Returns the payload in the
 * skb, ready to process. On a zero-length packet, we retry.
 *
 * On soft USB errors, we retry (until they become too frequent and
 * then are promoted to hard); on hard USB errors, we reset the
 * device. On other errors (skb realloacation, we just drop it and
 * hope for the next invocation to solve it).
 *
 * Returns: pointer to the skb if ok, ERR_PTR on error.
 *   NOTE: this function might realloc the skb (if it is too small),
 *   so always update with the one returned.
 *   ERR_PTR() is < 0 on error.
 *   Will return NULL if it cannot reallocate -- this can be
 *   considered a transient retryable error.
 */
static
struct sk_buff *i2400mu_rx(struct i2400mu *i2400mu, struct sk_buff *rx_skb)
{
        int result = 0;
        struct device *dev = &i2400mu->usb_iface->dev;
        int usb_pipe, read_size, rx_size, do_autopm;
        struct usb_endpoint_descriptor *epd;
        const size_t max_pkt_size = 512;

        d_fnstart(4, dev, "(i2400mu %p)\n", i2400mu);
        do_autopm = atomic_read(&i2400mu->do_autopm);
        result = do_autopm ?
                usb_autopm_get_interface(i2400mu->usb_iface) : 0;
        if (result < 0) {
                dev_err(dev, "RX: can't get autopm: %d\n", result);
                do_autopm = 0;
        }
        epd = usb_get_epd(i2400mu->usb_iface, i2400mu->endpoint_cfg.bulk_in);
        usb_pipe = usb_rcvbulkpipe(i2400mu->usb_dev, epd->bEndpointAddress);
retry:
        rx_size = skb_end_pointer(rx_skb) - rx_skb->data - rx_skb->len;
        if (unlikely(rx_size % max_pkt_size == 0)) {
                rx_size -= 8;
                d_printf(1, dev, "RX: rx_size adapted to %d [-8]\n", rx_size);
        }
        result = usb_bulk_msg(
                i2400mu->usb_dev, usb_pipe, rx_skb->data + rx_skb->len,
                rx_size, &read_size, 200);
        usb_mark_last_busy(i2400mu->usb_dev);
        switch (result) {
        case 0:
                if (read_size == 0)
                        goto retry;     /* ZLP, just resubmit */
                skb_put(rx_skb, read_size);
                break;
        case -EPIPE:
                /*
                 * Stall -- maybe the device is choking with our
                 * requests. Clear it and give it some time. If they
                 * happen to often, it might be another symptom, so we
                 * reset.
                 *
                 * No error handling for usb_clear_halt(0; if it
                 * works, the retry works; if it fails, this switch
                 * does the error handling for us.
                 */
                if (edc_inc(&i2400mu->urb_edc,
                            10 * EDC_MAX_ERRORS, EDC_ERROR_TIMEFRAME)) {
                        dev_err(dev, "BM-CMD: too many stalls in "
                                "URB; resetting device\n");
                        goto do_reset;
                }
                usb_clear_halt(i2400mu->usb_dev, usb_pipe);
                msleep(10);     /* give the device some time */
                goto retry;
        case -EINVAL:                   /* while removing driver */
        case -ENODEV:                   /* dev disconnect ... */
        case -ENOENT:                   /* just ignore it */
        case -ESHUTDOWN:
        case -ECONNRESET:
                break;
        case -EOVERFLOW: {              /* too small, reallocate */
                struct sk_buff *new_skb;
                rx_size = i2400mu_rx_size_grow(i2400mu);
                if (rx_size <= (1 << 16))       /* cap it */
                        i2400mu->rx_size = rx_size;
                else if (printk_ratelimit()) {
                        dev_err(dev, "BUG? rx_size up to %d\n", rx_size);
                        result = -EINVAL;
                        goto out;
                }
                skb_put(rx_skb, read_size);
                new_skb = skb_copy_expand(rx_skb, 0, rx_size - rx_skb->len,
                                          GFP_KERNEL);
                if (new_skb == NULL) {
                        if (printk_ratelimit())
                                dev_err(dev, "RX: Can't reallocate skb to %d; "
                                        "RX dropped\n", rx_size);
                        kfree_skb(rx_skb);
                        rx_skb = NULL;
                        goto out;       /* drop it...*/
                }
                kfree_skb(rx_skb);
                rx_skb = new_skb;
                i2400mu->rx_size_cnt = 0;
                i2400mu->rx_size_acc = i2400mu->rx_size;
                d_printf(1, dev, "RX: size changed to %d, received %d, "
                         "copied %d, capacity %ld\n",
                         rx_size, read_size, rx_skb->len,
                         (long) skb_end_offset(new_skb));
                goto retry;
        }
                /* In most cases, it happens due to the hardware scheduling a
                 * read when there was no data - unfortunately, we have no way
                 * to tell this timeout from a USB timeout. So we just ignore
                 * it. */
        case -ETIMEDOUT:
                dev_err(dev, "RX: timeout: %d\n", result);
                result = 0;
                break;
        default:                        /* Any error */
                if (edc_inc(&i2400mu->urb_edc,
                            EDC_MAX_ERRORS, EDC_ERROR_TIMEFRAME))
                        goto error_reset;
                dev_err(dev, "RX: error receiving URB: %d, retrying\n", result);
                goto retry;
        }
out:
        if (do_autopm)
                usb_autopm_put_interface(i2400mu->usb_iface);
        d_fnend(4, dev, "(i2400mu %p) = %p\n", i2400mu, rx_skb);
        return rx_skb;

error_reset:
        dev_err(dev, "RX: maximum errors in URB exceeded; "
                "resetting device\n");
do_reset:
        usb_queue_reset_device(i2400mu->usb_iface);
        rx_skb = ERR_PTR(result);
        goto out;
}


/*
 * Kernel thread for USB reception of data
 *
 * This thread waits for a kick; once kicked, it will allocate an skb
 * and receive a single message to it from USB (using
 * i2400mu_rx()). Once received, it is passed to the generic i2400m RX
 * code for processing.
 *
 * When done processing, it runs some dirty statistics to verify if
 * the last 100 messages received were smaller than half of the
 * current RX buffer size. In that case, the RX buffer size is
 * halved. This will helps lowering the pressure on the memory
 * allocator.
 *
 * Hard errors force the thread to exit.
 */
static
int i2400mu_rxd(void *_i2400mu)
{
        int result = 0;
        struct i2400mu *i2400mu = _i2400mu;
        struct i2400m *i2400m = &i2400mu->i2400m;
        struct device *dev = &i2400mu->usb_iface->dev;
        struct net_device *net_dev = i2400m->wimax_dev.net_dev;
        size_t pending;
        int rx_size;
        struct sk_buff *rx_skb;
        unsigned long flags;

        d_fnstart(4, dev, "(i2400mu %p)\n", i2400mu);
        spin_lock_irqsave(&i2400m->rx_lock, flags);
        BUG_ON(i2400mu->rx_kthread != NULL);
        i2400mu->rx_kthread = current;
        spin_unlock_irqrestore(&i2400m->rx_lock, flags);
        while (1) {
                d_printf(2, dev, "RX: waiting for messages\n");
                pending = 0;
                wait_event_interruptible(
                        i2400mu->rx_wq,
                        (kthread_should_stop()  /* check this first! */
                         || (pending = atomic_read(&i2400mu->rx_pending_count)))
                        );
                if (kthread_should_stop())
                        break;
                if (pending == 0)
                        continue;
                rx_size = i2400mu->rx_size;
                d_printf(2, dev, "RX: reading up to %d bytes\n", rx_size);
                rx_skb = __netdev_alloc_skb(net_dev, rx_size, GFP_KERNEL);
                if (rx_skb == NULL) {
                        dev_err(dev, "RX: can't allocate skb [%d bytes]\n",
                                rx_size);
                        msleep(50);     /* give it some time? */
                        continue;
                }

                /* Receive the message with the payloads */
                rx_skb = i2400mu_rx(i2400mu, rx_skb);
                result = PTR_ERR(rx_skb);
                if (IS_ERR(rx_skb))
                        goto out;
                atomic_dec(&i2400mu->rx_pending_count);
                if (rx_skb == NULL || rx_skb->len == 0) {
                        /* some "ignorable" condition */
                        kfree_skb(rx_skb);
                        continue;
                }

                /* Deliver the message to the generic i2400m code */
                i2400mu->rx_size_cnt++;
                i2400mu->rx_size_acc += rx_skb->len;
                result = i2400m_rx(i2400m, rx_skb);
                if (result == -EIO
                    && edc_inc(&i2400mu->urb_edc,
                               EDC_MAX_ERRORS, EDC_ERROR_TIMEFRAME)) {
                        goto error_reset;
                }

                /* Maybe adjust RX buffer size */
                i2400mu_rx_size_maybe_shrink(i2400mu);
        }
        result = 0;
out:
        spin_lock_irqsave(&i2400m->rx_lock, flags);
        i2400mu->rx_kthread = NULL;
        spin_unlock_irqrestore(&i2400m->rx_lock, flags);
        d_fnend(4, dev, "(i2400mu %p) = %d\n", i2400mu, result);
        return result;

error_reset:
        dev_err(dev, "RX: maximum errors in received buffer exceeded; "
                "resetting device\n");
        usb_queue_reset_device(i2400mu->usb_iface);
        goto out;
}


/*
 * Start reading from the device
 *
 * @i2400m: device instance
 *
 * Notify the RX thread that there is data pending.
 */
void i2400mu_rx_kick(struct i2400mu *i2400mu)
{
        struct i2400m *i2400m = &i2400mu->i2400m;
        struct device *dev = &i2400mu->usb_iface->dev;

        d_fnstart(3, dev, "(i2400mu %p)\n", i2400m);
        atomic_inc(&i2400mu->rx_pending_count);
        wake_up_all(&i2400mu->rx_wq);
        d_fnend(3, dev, "(i2400m %p) = void\n", i2400m);
}


int i2400mu_rx_setup(struct i2400mu *i2400mu)
{
        int result = 0;
        struct i2400m *i2400m = &i2400mu->i2400m;
        struct device *dev = &i2400mu->usb_iface->dev;
        struct wimax_dev *wimax_dev = &i2400m->wimax_dev;
        struct task_struct *kthread;

        kthread = kthread_run(i2400mu_rxd, i2400mu, "%s-rx",
                              wimax_dev->name);
        /* the kthread function sets i2400mu->rx_thread */
        if (IS_ERR(kthread)) {
                result = PTR_ERR(kthread);
                dev_err(dev, "RX: cannot start thread: %d\n", result);
        }
        return result;
}


void i2400mu_rx_release(struct i2400mu *i2400mu)
{
        unsigned long flags;
        struct i2400m *i2400m = &i2400mu->i2400m;
        struct device *dev = i2400m_dev(i2400m);
        struct task_struct *kthread;

        spin_lock_irqsave(&i2400m->rx_lock, flags);
        kthread = i2400mu->rx_kthread;
        i2400mu->rx_kthread = NULL;
        spin_unlock_irqrestore(&i2400m->rx_lock, flags);
        if (kthread)
                kthread_stop(kthread);
        else
                d_printf(1, dev, "RX: kthread had already exited\n");
}