/*      $NetBSD: dma.c,v 1.29 2023/01/06 10:28:28 tsutsui Exp $ */

/*
 * Copyright (c) 1995 Leo Weppelman.
 * All rights reserved.
 *
 * 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.
 *
 * 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.
 */

/*
 * This file contains special code dealing with the DMA interface
 * on the Atari ST.
 *
 * The DMA circuitry requires some special treatment for the peripheral
 * devices which make use of the ST's DMA feature (the hard disk and the
 * floppy drive).
 * All devices using DMA need mutually exclusive access and can follow some
 * standard pattern which will be provided in this file.
 *
 * The file contains the following entry points:
 *
 *      st_dmagrab:     ensure exclusive access to the DMA circuitry
 *      st_dmafree:     free exclusive access to the DMA circuitry
 *      st_dmawanted:   somebody is queued waiting for DMA-access
 *      dmaint:         DMA interrupt routine, switches to the current driver
 *      st_dmaaddr_set: specify 24 bit RAM address
 *      st_dmaaddr_get: get address of last DMA-op
 *      st_dmacomm:     program DMA, flush FIFO first
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: dma.c,v 1.29 2023/01/06 10:28:28 tsutsui Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/queue.h>

#include <machine/cpu.h>
#include <machine/iomap.h>
#include <machine/dma.h>
#include <machine/intr.h>

#define NDMA_DEV        10      /* Max 2 floppy's, 8 hard-disks         */
typedef struct dma_entry {
        TAILQ_ENTRY(dma_entry)  entries;        /* List pointers           */
        void            (*call_func)(void *);   /* Call when lock granted  */
        void            (*int_func)(void *);    /* Call on DMA interrupt   */
        void            *softc;                 /* Arg. to int_func        */
        int             *lock_stat;             /* status of DMA lock      */
} DMA_ENTRY;

/*
 * Preallocated entries. An allocator seem an overkill here.
 */
static  DMA_ENTRY dmatable[NDMA_DEV];   /* preallocated entries         */

/*
 * Heads of free and active lists:
 */
static  TAILQ_HEAD(freehead, dma_entry) dma_free;
static  TAILQ_HEAD(acthead, dma_entry)  dma_active;

static  int     must_init = 1;          /* Must initialize              */

int     cdmaint(void *, int);

static  void    st_dma_init(void);

static void
st_dma_init(void)
{
        int i;

        TAILQ_INIT(&dma_free);
        TAILQ_INIT(&dma_active);

        for (i = 0; i < NDMA_DEV; i++)
                TAILQ_INSERT_HEAD(&dma_free, &dmatable[i], entries);

        if (intr_establish(7, USER_VEC, 0, cdmaint, NULL) == NULL)
                panic("st_dma_init: Can't establish interrupt");
}

int
st_dmagrab(dma_farg int_func, dma_farg call_func, void *softc, int *lock_stat,
    int rcaller, kmutex_t *interlock)
{
        int s;
        DMA_ENTRY *req;

        if (must_init) {
                st_dma_init();
                must_init = 0;
        }
        *lock_stat = DMA_LOCK_REQ;

        s = splhigh();

        /*
         * Create a request...
         */
        if ((req = TAILQ_FIRST(&dma_free)) == NULL)
                panic("st_dmagrab: Too many outstanding requests");
        TAILQ_REMOVE(&dma_free, req, entries);
        req->call_func = call_func;
        req->int_func  = int_func;
        req->softc     = softc;
        req->lock_stat = lock_stat;
        TAILQ_INSERT_TAIL(&dma_active, req, entries);

        if (TAILQ_FIRST(&dma_active) != req) {
                if (call_func == NULL) {
                        do {
                                mtsleep(&dma_active, PRIBIO, "dmalck", 0,
                                    interlock);
                        } while (*req->lock_stat != DMA_LOCK_GRANT);
                        splx(s);
                        return 1;
                }
                splx(s);
                return 0;
        }
        splx(s);

        /*
         * We're at the head of the queue, ergo: we got the lock.
         */
        *lock_stat = DMA_LOCK_GRANT;

        if (rcaller || (call_func == NULL)) {
                /*
                 * Just return to caller immediately without going
                 * through 'call_func' first.
                 */
                return 1;
        }

        (*call_func)(softc);    /* Call followup function               */
        return 0;
}

void
st_dmafree(void *softc, int *lock_stat)
{
        int s;
        DMA_ENTRY *req;

        s = splhigh();

        /*
         * Some validity checks first.
         */
        if ((req = TAILQ_FIRST(&dma_active)) == NULL)
                panic("st_dmafree: empty active queue");
        if (req->softc != softc)
                printf("Caller of st_dmafree is not lock-owner!\n");

        /*
         * Clear lock status, move request from active to free queue.
         */
        *lock_stat = 0;
        TAILQ_REMOVE(&dma_active, req, entries);
        TAILQ_INSERT_HEAD(&dma_free, req, entries);

        if ((req = TAILQ_FIRST(&dma_active)) != NULL) {
                *req->lock_stat = DMA_LOCK_GRANT;

                if (req->call_func == NULL)
                        wakeup((void *)&dma_active);
                else {
                        /*
                         * Call next request through softint handler.
                         * This avoids spl-conflicts.
                         */
                        add_sicallback((si_farg)req->call_func, req->softc, 0);
                }
        }
        splx(s);
}

int
st_dmawanted(void)
{

        return TAILQ_NEXT(TAILQ_FIRST(&dma_active), entries) != NULL;
}

int
cdmaint(void *unused, int sr)
        /* sr:   sr at time of interrupt */
{
        dma_farg int_func;
        void *softc;

        if (TAILQ_FIRST(&dma_active) != NULL) {
                /*
                 * Due to the logic of the ST-DMA chip, it is not possible to
                 * check for stray interrupts here...
                 */
                int_func = TAILQ_FIRST(&dma_active)->int_func;
                softc    = TAILQ_FIRST(&dma_active)->softc;
                add_sicallback((si_farg)int_func, softc, 0);
                return 1;
        }
        return 0;
}

/*
 * Setup address for DMA-transfer.
 * Note: The order _is_ important!
 */
void
st_dmaaddr_set(void *address)
{
        u_long ad = (u_long)address;

        DMA->dma_addr[AD_LOW ] = (ad     ) & 0xff;
        DMA->dma_addr[AD_MID ] = (ad >> 8) & 0xff;
        DMA->dma_addr[AD_HIGH] = (ad >>16) & 0xff;
}

/*
 * Get address from DMA unit.
 */
u_long
st_dmaaddr_get(void)
{
        u_long ad = 0;

        ad  = (DMA->dma_addr[AD_LOW ] & 0xff);
        ad |= (DMA->dma_addr[AD_MID ] & 0xff) << 8;
        ad |= (DMA->dma_addr[AD_HIGH] & 0xff) <<16;
        return ad;
}

/*
 * Program the DMA-controller to transfer 'nblk' blocks of 512 bytes.
 * The DMA_WRBIT trick flushes the FIFO before doing DMA.
 */
void
st_dmacomm(int mode, int nblk)
{

        DMA->dma_mode = mode;
        DMA->dma_mode = mode ^ DMA_WRBIT;
        DMA->dma_mode = mode;
        DMA->dma_data = nblk;
        delay(2);       /* Needed for Falcon */
        DMA->dma_mode = DMA_SCREG | (mode & DMA_WRBIT);
}