lser.c

/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *      The President and Fellows of Harvard College.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the University 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 UNIVERSITY 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 UNIVERSITY 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.
 */

#include <types.h>
#include <lib.h>
#include <spinlock.h>
#include <platform/bus.h>
#include <lamebus/lser.h>
#include "autoconf.h"

/* Registers (offsets within slot) */
#define LSER_REG_CHAR  0     /* Character in/out */
#define LSER_REG_WIRQ  4     /* Write interrupt status */
#define LSER_REG_RIRQ  8     /* Read interrupt status */

/* Bits in the IRQ registers */
#define LSER_IRQ_ENABLE  1
#define LSER_IRQ_ACTIVE  2

void
lser_irq(void *vsc)
{
        struct lser_softc *sc = vsc;
        uint32_t x;
        bool clear_to_write = false;
        bool got_a_read = false;
        uint32_t ch = 0;

        spinlock_acquire(&sc->ls_lock);

        x = bus_read_register(sc->ls_busdata, sc->ls_buspos, LSER_REG_WIRQ);
        if (x & LSER_IRQ_ACTIVE) {
                x = LSER_IRQ_ENABLE;
                sc->ls_wbusy = 0;
                clear_to_write = true;
                bus_write_register(sc->ls_busdata, sc->ls_buspos,
                                   LSER_REG_WIRQ, x);
        }

        x = bus_read_register(sc->ls_busdata, sc->ls_buspos, LSER_REG_RIRQ);
        if (x & LSER_IRQ_ACTIVE) {
                x = LSER_IRQ_ENABLE;
                ch = bus_read_register(sc->ls_busdata, sc->ls_buspos,
                                       LSER_REG_CHAR);
                got_a_read = true;
                bus_write_register(sc->ls_busdata, sc->ls_buspos, 
                                   LSER_REG_RIRQ, x);
        }

        spinlock_release(&sc->ls_lock);

        if (clear_to_write && sc->ls_start != NULL) {
                sc->ls_start(sc->ls_devdata);
        }
        if (got_a_read && sc->ls_input != NULL) {
                sc->ls_input(sc->ls_devdata, ch);
        }
}

void
lser_write(void *vls, int ch)
{
        struct lser_softc *ls = vls;

        spinlock_acquire(&ls->ls_lock);

        if (ls->ls_wbusy) {
                /*
                 * We're not clear to write.
                 *
                 * This should not happen. It's the job of the driver
                 * attached to us to not write until we call
                 * ls->ls_start.
                 *
                 * (Note: if we're the console, the panic will go to
                 * lser_writepolled for printing, because we hold a
                 * spinlock and interrupts are off; it won't recurse.)
                 */
                panic("lser: Not clear to write\n");
        }
        ls->ls_wbusy = true;

        bus_write_register(ls->ls_busdata, ls->ls_buspos, LSER_REG_CHAR, ch);

        spinlock_release(&ls->ls_lock);
}

static
void
lser_poll_until_write(struct lser_softc *sc)
{
        uint32_t val;

        KASSERT(spinlock_do_i_hold(&sc->ls_lock));

        do {
                val = bus_read_register(sc->ls_busdata, sc->ls_buspos,
                                        LSER_REG_WIRQ);
        }
        while ((val & LSER_IRQ_ACTIVE) == 0);
}

void
lser_writepolled(void *vsc, int ch)
{
        struct lser_softc *sc = vsc;
        bool irqpending = false;

        spinlock_acquire(&sc->ls_lock);

        if (sc->ls_wbusy) {
                irqpending = true;
                lser_poll_until_write(sc);
                /* Clear the ready condition */
                bus_write_register(sc->ls_busdata, sc->ls_buspos,
                                   LSER_REG_WIRQ, LSER_IRQ_ENABLE);
        }

        /* Send the character. */
        bus_write_register(sc->ls_busdata, sc->ls_buspos, LSER_REG_CHAR, ch);

        /* Wait until it's done. */
        lser_poll_until_write(sc);

        /*
         * If there wasn't already an IRQ pending, clear the ready condition.
         * But if there was, leave the ready condition, so we get to the 
         * interrupt handler in due course.
         */
        if (!irqpending) {
                bus_write_register(sc->ls_busdata, sc->ls_buspos,
                                   LSER_REG_WIRQ, LSER_IRQ_ENABLE);
        }

        spinlock_release(&sc->ls_lock);
}

/*
 * Mask the interrupt while we're writing in polling mode. Doing so
 * causes the interrupt line to flap on every character, which makes
 * the CPU receiving those interrupts upset.
 */
void
lser_startpolling(void *vsc)
{
        struct lser_softc *sc = vsc;
        sc->ls_maskinterrupt(sc->ls_busdata, sc->ls_buspos);
}

void
lser_endpolling(void *vsc)
{
        struct lser_softc *sc = vsc;
        sc->ls_unmaskinterrupt(sc->ls_busdata, sc->ls_buspos);
}

int
config_lser(struct lser_softc *sc, int lserno)
{
        (void)lserno;

        /*
         * Enable interrupting.
         */

        spinlock_init(&sc->ls_lock);
        sc->ls_wbusy = false;

        bus_write_register(sc->ls_busdata, sc->ls_buspos,
                           LSER_REG_RIRQ, LSER_IRQ_ENABLE);
        bus_write_register(sc->ls_busdata, sc->ls_buspos,
                           LSER_REG_WIRQ, LSER_IRQ_ENABLE);

        return 0;
}