source: mainline/uspace/lib/usbhost/src/bandwidth.c@ 9bfa8c8

/*
 * SPDX-FileCopyrightText: 2011 Jan Vesely
 * SPDX-FileCopyrightText: 2018 Ondrej Hlavaty
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
/**  @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"

/** Bytes per second in FULL SPEED */
#define BANDWIDTH_TOTAL_USB11 (12000000 / 8)
/** 90% of total bandwidth is available for periodic transfers */
#define BANDWIDTH_AVAILABLE_USB11 ((BANDWIDTH_TOTAL_USB11 * 9) / 10)

/**
 * Calculate bandwidth that needs to be reserved for communication with EP.
 * Calculation follows USB 1.1 specification.
 *
 * @param ep An endpoint for which the bandwidth is to be counted
 */
static size_t bandwidth_count_usb11(endpoint_t *ep)
{
        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 size_t packet_count = ep->packets_per_uframe;

        /*
         * 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;
        }
}

const bandwidth_accounting_t bandwidth_accounting_usb11 = {
        .available_bandwidth = BANDWIDTH_AVAILABLE_USB11,
        .count_bw = &bandwidth_count_usb11,
};

/** Number of nanoseconds in one microframe */
#define BANDWIDTH_TOTAL_USB2 (125000)
/** 90% of total bandwidth is available for periodic transfers */
#define BANDWIDTH_AVAILABLE_USB2  ((BANDWIDTH_TOTAL_USB2 * 9) / 10)

/**
 * Calculate bandwidth that needs to be reserved for communication with EP.
 * Calculation follows USB 2.0 specification, chapter 5.11.3.
 *
 * FIXME: Interrupt transfers shall be probably divided by their polling interval.
 *
 * @param ep An endpoint for which the bandwidth is to be counted
 * @return Number of nanoseconds transaction with @c size bytes payload will
 *         take.
 */
static size_t bandwidth_count_usb2(endpoint_t *ep)
{
        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;
        }

        // 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 = (ep->max_transfer_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;
        }
}

const bandwidth_accounting_t bandwidth_accounting_usb2 = {
        .available_bandwidth = BANDWIDTH_AVAILABLE_USB2,
        .count_bw = &bandwidth_count_usb2,
};