// SPDX-License-Identifier: GPL-2.0
/*
 * Driver for the ADB controller in the Mac I/O (Hydra) chip.
 */
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/pgtable.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/adb.h>

#include <asm/io.h>
#include <asm/hydra.h>
#include <asm/irq.h>
#include <linux/init.h>
#include <linux/ioport.h>

struct preg {
        unsigned char r;
        char pad[15];
};

struct adb_regs {
        struct preg intr;
        struct preg data[9];
        struct preg intr_enb;
        struct preg dcount;
        struct preg error;
        struct preg ctrl;
        struct preg autopoll;
        struct preg active_hi;
        struct preg active_lo;
        struct preg test;
};

/* Bits in intr and intr_enb registers */
#define DFB     1               /* data from bus */
#define TAG     2               /* transfer access grant */

/* Bits in dcount register */
#define HMB     0x0f            /* how many bytes */
#define APD     0x10            /* auto-poll data */

/* Bits in error register */
#define NRE     1               /* no response error */
#define DLE     2               /* data lost error */

/* Bits in ctrl register */
#define TAR     1               /* transfer access request */
#define DTB     2               /* data to bus */
#define CRE     4               /* command response expected */
#define ADB_RST 8               /* ADB reset */

/* Bits in autopoll register */
#define APE     1               /* autopoll enable */

static volatile struct adb_regs __iomem *adb;
static struct adb_request *current_req, *last_req;
static DEFINE_SPINLOCK(macio_lock);

static int macio_probe(void);
static int macio_init(void);
static irqreturn_t macio_adb_interrupt(int irq, void *arg);
static int macio_send_request(struct adb_request *req, int sync);
static int macio_adb_autopoll(int devs);
static void macio_adb_poll(void);
static int macio_adb_reset_bus(void);

struct adb_driver macio_adb_driver = {
        .name         = "MACIO",
        .probe        = macio_probe,
        .init         = macio_init,
        .send_request = macio_send_request,
        .autopoll     = macio_adb_autopoll,
        .poll         = macio_adb_poll,
        .reset_bus    = macio_adb_reset_bus,
};

int macio_probe(void)
{
        struct device_node *np __free(device_node) =
                of_find_compatible_node(NULL, "adb", "chrp,adb0");

        if (np)
                return 0;

        return -ENODEV;
}

int macio_init(void)
{
        struct device_node *adbs __free(device_node) =
                of_find_compatible_node(NULL, "adb", "chrp,adb0");
        struct resource r;
        unsigned int irq;

        if (!adbs)
                return -ENXIO;

        if (of_address_to_resource(adbs, 0, &r))
                return -ENXIO;

        adb = ioremap(r.start, sizeof(struct adb_regs));
        if (!adb)
                return -ENOMEM;


        out_8(&adb->ctrl.r, 0);
        out_8(&adb->intr.r, 0);
        out_8(&adb->error.r, 0);
        out_8(&adb->active_hi.r, 0xff); /* for now, set all devices active */
        out_8(&adb->active_lo.r, 0xff);
        out_8(&adb->autopoll.r, APE);

        irq = irq_of_parse_and_map(adbs, 0);
        if (request_irq(irq, macio_adb_interrupt, 0, "ADB", (void *)0)) {
                iounmap(adb);
                printk(KERN_ERR "ADB: can't get irq %d\n", irq);
                return -EAGAIN;
        }
        out_8(&adb->intr_enb.r, DFB | TAG);

        printk("adb: mac-io driver 1.0 for unified ADB\n");

        return 0;
}

static int macio_adb_autopoll(int devs)
{
        unsigned long flags;
        
        spin_lock_irqsave(&macio_lock, flags);
        out_8(&adb->active_hi.r, devs >> 8);
        out_8(&adb->active_lo.r, devs);
        out_8(&adb->autopoll.r, devs? APE: 0);
        spin_unlock_irqrestore(&macio_lock, flags);
        return 0;
}

static int macio_adb_reset_bus(void)
{
        unsigned long flags;
        int timeout = 1000000;

        /* Hrm... we may want to not lock interrupts for so
         * long ... oh well, who uses that chip anyway ? :)
         * That function will be seldom used during boot
         * on rare machines, so...
         */
        spin_lock_irqsave(&macio_lock, flags);
        out_8(&adb->ctrl.r, in_8(&adb->ctrl.r) | ADB_RST);
        while ((in_8(&adb->ctrl.r) & ADB_RST) != 0) {
                if (--timeout == 0) {
                        out_8(&adb->ctrl.r, in_8(&adb->ctrl.r) & ~ADB_RST);
                        spin_unlock_irqrestore(&macio_lock, flags);
                        return -1;
                }
        }
        spin_unlock_irqrestore(&macio_lock, flags);
        return 0;
}

/* Send an ADB command */
static int macio_send_request(struct adb_request *req, int sync)
{
        unsigned long flags;
        int i;
        
        if (req->data[0] != ADB_PACKET)
                return -EINVAL;
        
        for (i = 0; i < req->nbytes - 1; ++i)
                req->data[i] = req->data[i+1];
        --req->nbytes;
        
        req->next = NULL;
        req->sent = 0;
        req->complete = 0;
        req->reply_len = 0;

        spin_lock_irqsave(&macio_lock, flags);
        if (current_req) {
                last_req->next = req;
                last_req = req;
        } else {
                current_req = last_req = req;
                out_8(&adb->ctrl.r, in_8(&adb->ctrl.r) | TAR);
        }
        spin_unlock_irqrestore(&macio_lock, flags);
        
        if (sync) {
                while (!req->complete)
                        macio_adb_poll();
        }

        return 0;
}

static irqreturn_t macio_adb_interrupt(int irq, void *arg)
{
        int i, n, err;
        struct adb_request *req = NULL;
        unsigned char ibuf[16];
        int ibuf_len = 0;
        int complete = 0;
        int autopoll = 0;
        int handled = 0;

        spin_lock(&macio_lock);
        if (in_8(&adb->intr.r) & TAG) {
                handled = 1;
                req = current_req;
                if (req) {
                        /* put the current request in */
                        for (i = 0; i < req->nbytes; ++i)
                                out_8(&adb->data[i].r, req->data[i]);
                        out_8(&adb->dcount.r, req->nbytes & HMB);
                        req->sent = 1;
                        if (req->reply_expected) {
                                out_8(&adb->ctrl.r, DTB + CRE);
                        } else {
                                out_8(&adb->ctrl.r, DTB);
                                current_req = req->next;
                                complete = 1;
                                if (current_req)
                                        out_8(&adb->ctrl.r, in_8(&adb->ctrl.r) | TAR);
                        }
                }
                out_8(&adb->intr.r, 0);
        }

        if (in_8(&adb->intr.r) & DFB) {
                handled = 1;
                err = in_8(&adb->error.r);
                if (current_req && current_req->sent) {
                        /* this is the response to a command */
                        req = current_req;
                        if (err == 0) {
                                req->reply_len = in_8(&adb->dcount.r) & HMB;
                                for (i = 0; i < req->reply_len; ++i)
                                        req->reply[i] = in_8(&adb->data[i].r);
                        }
                        current_req = req->next;
                        complete = 1;
                        if (current_req)
                                out_8(&adb->ctrl.r, in_8(&adb->ctrl.r) | TAR);
                } else if (err == 0) {
                        /* autopoll data */
                        n = in_8(&adb->dcount.r) & HMB;
                        for (i = 0; i < n; ++i)
                                ibuf[i] = in_8(&adb->data[i].r);
                        ibuf_len = n;
                        autopoll = (in_8(&adb->dcount.r) & APD) != 0;
                }
                out_8(&adb->error.r, 0);
                out_8(&adb->intr.r, 0);
        }
        spin_unlock(&macio_lock);
        if (complete && req) {
            void (*done)(struct adb_request *) = req->done;
            mb();
            req->complete = 1;
            /* Here, we assume that if the request has a done member, the
             * struct request will survive to setting req->complete to 1
             */
            if (done)
                (*done)(req);
        }
        if (ibuf_len)
                adb_input(ibuf, ibuf_len, autopoll);

        return IRQ_RETVAL(handled);
}

static void macio_adb_poll(void)
{
        unsigned long flags;

        local_irq_save(flags);
        if (in_8(&adb->intr.r) != 0)
                macio_adb_interrupt(0, NULL);
        local_irq_restore(flags);
}