source: mainline/uspace/lib/usbhost/src/bandwidth.c@ 1102eca

/*
 * Copyright (c) 2011 Jan Vesely
 * 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */
/**  @addtogroup libusbhost
 * @{
 */
/** @file
 *
 * Bandwidth calculation functions. Shared among uhci, ohci and ehci drivers.
 */

#include <assert.h>
#include <stdlib.h>

#include "endpoint.h"
#include "bus.h"

#include "bandwidth.h"

/**
 * Calculate bandwidth that needs to be reserved for communication with EP.
 * Calculation follows USB 1.1 specification.
 * @param ep Registered endpoint
 * @param size Number of bytes to transfer.
 * @param max_packet_size Maximum bytes in one packet.
 */
ssize_t bandwidth_count_usb11(endpoint_t *ep, size_t size)
{
        assert(ep);
        assert(ep->device);

        const usb_transfer_type_t type = ep->transfer_type;

        /* We care about bandwidth only for interrupt and isochronous. */
        if ((type != USB_TRANSFER_INTERRUPT)
            && (type != USB_TRANSFER_ISOCHRONOUS)) {
                return 0;
        }

        const size_t max_packet_size = ep->max_packet_size;

        const unsigned packet_count =
            (size + max_packet_size - 1) / max_packet_size;
        /* TODO: It may be that ISO and INT transfers use only one packet per
         * transaction, but I did not find text in USB spec to confirm this */
        /* NOTE: All data packets will be considered to be max_packet_size */
        switch (ep->device->speed)
        {
        case USB_SPEED_LOW:
                assert(type == USB_TRANSFER_INTERRUPT);
                /* Protocol overhead 13B
                 * (3 SYNC bytes, 3 PID bytes, 2 Endpoint + CRC bytes, 2
                 * CRC bytes, and a 3-byte interpacket delay)
                 * see USB spec page 45-46. */
                /* Speed penalty 8: low speed is 8-times slower*/
                return packet_count * (13 + max_packet_size) * 8;
        case USB_SPEED_FULL:
                /* Interrupt transfer overhead see above
                 * or page 45 of USB spec */
                if (type == USB_TRANSFER_INTERRUPT)
                        return packet_count * (13 + max_packet_size);

                assert(type == USB_TRANSFER_ISOCHRONOUS);
                /* Protocol overhead 9B
                 * (2 SYNC bytes, 2 PID bytes, 2 Endpoint + CRC bytes, 2 CRC
                 * bytes, and a 1-byte interpacket delay)
                 * see USB spec page 42 */
                return packet_count * (9 + max_packet_size);
        default:
                return 0;
        }
}

/** 
 * Calculate bandwidth that needs to be reserved for communication with EP.
 * Calculation follows USB 2.0 specification, chapter 5.11.3.
 *
 * @param speed Device's speed.
 * @param type Type of the transfer.
 * @param size Number of byte to transfer.
 * @param max_packet_size Maximum bytes in one packet.
 * @return Number of nanoseconds transaction with @c size bytes payload will
 *         take.
 */
ssize_t bandwidth_count_usb20(endpoint_t *ep, size_t size)
{
        assert(ep);

        const usb_transfer_type_t type = ep->transfer_type;

        /* We care about bandwidth only for interrupt and isochronous. */
        if ((type != USB_TRANSFER_INTERRUPT)
            && (type != USB_TRANSFER_ISOCHRONOUS)) {
                return 0;
        }

        // FIXME: Come up with some upper bound for these (in ns).
        const size_t host_delay = 0;
        const size_t hub_ls_setup = 0;

        // Approx. Floor(3.167 + BitStuffTime(Data_bc))
        const size_t base_time = (size * 8 + 19) / 6;

        switch (ep->device->speed) {
        case USB_SPEED_LOW:
                if (ep->direction == USB_DIRECTION_IN)
                        return 64060 + (2 * hub_ls_setup) + (677 * base_time) + host_delay;
                else
                        return 64107 + (2 * hub_ls_setup) + (667 * base_time) + host_delay;

        case USB_SPEED_FULL:
                if (ep->transfer_type == USB_TRANSFER_INTERRUPT)
                        return 9107 + 84 * base_time + host_delay;

                if (ep->direction == USB_DIRECTION_IN)
                        return 7268 + 84 * base_time + host_delay;
                else
                        return 6265 + 84 * base_time + host_delay;

        case USB_SPEED_HIGH:
                if (ep->transfer_type == USB_TRANSFER_INTERRUPT)
                        return (3648 + 25 * base_time + 11) / 12 + host_delay;
                else
                        return (5280 + 25 * base_time + 11) / 12 + host_delay;

        default:
                return 0;
        }
}