// SPDX-License-Identifier: GPL-2.0
/*
 * Device driver for the via ADB on (many) Mac II-class machines
 *
 * Based on the original ADB keyboard handler Copyright (c) 1997 Alan Cox
 * Also derived from code Copyright (C) 1996 Paul Mackerras.
 *
 * With various updates provided over the years by Michael Schmitz,
 * Guideo Koerber and others.
 *
 * Rewrite for Unified ADB by Joshua M. Thompson (funaho@jurai.org)
 *
 * 1999-08-02 (jmt) - Initial rewrite for Unified ADB.
 * 2000-03-29 Tony Mantler <tonym@mac.linux-m68k.org>
 *            - Big overhaul, should actually work now.
 * 2006-12-31 Finn Thain - Another overhaul.
 *
 * Suggested reading:
 *   Inside Macintosh, ch. 5 ADB Manager
 *   Guide to the Macinstosh Family Hardware, ch. 8 Apple Desktop Bus
 *   Rockwell R6522 VIA datasheet
 *
 * Apple's "ADB Analyzer" bus sniffer is invaluable:
 *   ftp://ftp.apple.com/developer/Tool_Chest/Devices_-_Hardware/Apple_Desktop_Bus/
 */
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/adb.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <asm/macintosh.h>
#include <asm/macints.h>
#include <asm/mac_via.h>

static volatile unsigned char *via;

/* VIA registers - spaced 0x200 bytes apart */
#define RS              0x200           /* skip between registers */
#define B               0               /* B-side data */
#define A               RS              /* A-side data */
#define DIRB            (2*RS)          /* B-side direction (1=output) */
#define DIRA            (3*RS)          /* A-side direction (1=output) */
#define T1CL            (4*RS)          /* Timer 1 ctr/latch (low 8 bits) */
#define T1CH            (5*RS)          /* Timer 1 counter (high 8 bits) */
#define T1LL            (6*RS)          /* Timer 1 latch (low 8 bits) */
#define T1LH            (7*RS)          /* Timer 1 latch (high 8 bits) */
#define T2CL            (8*RS)          /* Timer 2 ctr/latch (low 8 bits) */
#define T2CH            (9*RS)          /* Timer 2 counter (high 8 bits) */
#define SR              (10*RS)         /* Shift register */
#define ACR             (11*RS)         /* Auxiliary control register */
#define PCR             (12*RS)         /* Peripheral control register */
#define IFR             (13*RS)         /* Interrupt flag register */
#define IER             (14*RS)         /* Interrupt enable register */
#define ANH             (15*RS)         /* A-side data, no handshake */

/* Bits in B data register: all active low */
#define CTLR_IRQ        0x08            /* Controller rcv status (input) */
#define ST_MASK         0x30            /* mask for selecting ADB state bits */

/* Bits in ACR */
#define SR_CTRL         0x1c            /* Shift register control bits */
#define SR_EXT          0x0c            /* Shift on external clock */
#define SR_OUT          0x10            /* Shift out if 1 */

/* Bits in IFR and IER */
#define IER_SET         0x80            /* set bits in IER */
#define IER_CLR         0               /* clear bits in IER */
#define SR_INT          0x04            /* Shift register full/empty */

/* ADB transaction states according to GMHW */
#define ST_CMD          0x00            /* ADB state: command byte */
#define ST_EVEN         0x10            /* ADB state: even data byte */
#define ST_ODD          0x20            /* ADB state: odd data byte */
#define ST_IDLE         0x30            /* ADB state: idle, nothing to send */

/* ADB command byte structure */
#define ADDR_MASK       0xF0
#define CMD_MASK        0x0F
#define OP_MASK         0x0C
#define TALK            0x0C

static int macii_init_via(void);
static void macii_start(void);
static irqreturn_t macii_interrupt(int irq, void *arg);
static void macii_queue_poll(void);

static int macii_probe(void);
static int macii_init(void);
static int macii_send_request(struct adb_request *req, int sync);
static int macii_write(struct adb_request *req);
static int macii_autopoll(int devs);
static void macii_poll(void);
static int macii_reset_bus(void);

struct adb_driver via_macii_driver = {
        .name         = "Mac II",
        .probe        = macii_probe,
        .init         = macii_init,
        .send_request = macii_send_request,
        .autopoll     = macii_autopoll,
        .poll         = macii_poll,
        .reset_bus    = macii_reset_bus,
};

static enum macii_state {
        idle,
        sending,
        reading,
} macii_state;

static struct adb_request *current_req; /* first request struct in the queue */
static struct adb_request *last_req;     /* last request struct in the queue */
static unsigned char reply_buf[16];        /* storage for autopolled replies */
static unsigned char *reply_ptr;     /* next byte in reply_buf or req->reply */
static bool reading_reply;       /* store reply in reply_buf else req->reply */
static int data_index;      /* index of the next byte to send from req->data */
static int reply_len; /* number of bytes received in reply_buf or req->reply */
static int status;          /* VIA's ADB status bits captured upon interrupt */
static bool bus_timeout;                   /* no data was sent by the device */
static bool srq_asserted;    /* have to poll for the device that asserted it */
static u8 last_cmd;              /* the most recent command byte transmitted */
static u8 last_talk_cmd;    /* the most recent Talk command byte transmitted */
static u8 last_poll_cmd; /* the most recent Talk R0 command byte transmitted */
static unsigned int autopoll_devs;  /* bits set are device addresses to poll */

/* Check for MacII style ADB */
static int macii_probe(void)
{
        if (macintosh_config->adb_type != MAC_ADB_II)
                return -ENODEV;

        via = via1;

        pr_info("adb: Mac II ADB Driver v1.0 for Unified ADB\n");
        return 0;
}

/* Initialize the driver */
static int macii_init(void)
{
        unsigned long flags;
        int err;

        local_irq_save(flags);

        err = macii_init_via();
        if (err)
                goto out;

        err = request_irq(IRQ_MAC_ADB, macii_interrupt, 0, "ADB",
                          macii_interrupt);
        if (err)
                goto out;

        macii_state = idle;
out:
        local_irq_restore(flags);
        return err;
}

/* initialize the hardware */
static int macii_init_via(void)
{
        unsigned char x;

        /* We want CTLR_IRQ as input and ST_EVEN | ST_ODD as output lines. */
        via[DIRB] = (via[DIRB] | ST_EVEN | ST_ODD) & ~CTLR_IRQ;

        /* Set up state: idle */
        via[B] |= ST_IDLE;

        /* Shift register on input */
        via[ACR] = (via[ACR] & ~SR_CTRL) | SR_EXT;

        /* Wipe any pending data and int */
        x = via[SR];

        return 0;
}

/* Send an ADB poll (Talk Register 0 command prepended to the request queue) */
static void macii_queue_poll(void)
{
        static struct adb_request req;
        unsigned char poll_command;
        unsigned int poll_addr;

        /* This only polls devices in the autopoll list, which assumes that
         * unprobed devices never assert SRQ. That could happen if a device was
         * plugged in after the adb bus scan. Unplugging it again will resolve
         * the problem. This behaviour is similar to MacOS.
         */
        if (!autopoll_devs)
                return;

        /* The device most recently polled may not be the best device to poll
         * right now. Some other device(s) may have signalled SRQ (the active
         * device won't do that). Or the autopoll list may have been changed.
         * Try polling the next higher address.
         */
        poll_addr = (last_poll_cmd & ADDR_MASK) >> 4;
        if ((srq_asserted && last_cmd == last_poll_cmd) ||
            !(autopoll_devs & (1 << poll_addr))) {
                unsigned int higher_devs;

                higher_devs = autopoll_devs & -(1 << (poll_addr + 1));
                poll_addr = ffs(higher_devs ? higher_devs : autopoll_devs) - 1;
        }

        /* Send a Talk Register 0 command */
        poll_command = ADB_READREG(poll_addr, 0);

        /* No need to repeat this Talk command. The transceiver will do that
         * as long as it is idle.
         */
        if (poll_command == last_cmd)
                return;

        adb_request(&req, NULL, ADBREQ_NOSEND, 1, poll_command);

        req.sent = 0;
        req.complete = 0;
        req.reply_len = 0;
        req.next = current_req;

        if (WARN_ON(current_req)) {
                current_req = &req;
        } else {
                current_req = &req;
                last_req = &req;
        }
}

/* Send an ADB request; if sync, poll out the reply 'till it's done */
static int macii_send_request(struct adb_request *req, int sync)
{
        int err;

        err = macii_write(req);
        if (err)
                return err;

        if (sync)
                while (!req->complete)
                        macii_poll();

        return 0;
}

/* Send an ADB request (append to request queue) */
static int macii_write(struct adb_request *req)
{
        unsigned long flags;

        if (req->nbytes < 2 || req->data[0] != ADB_PACKET || req->nbytes > 15) {
                req->complete = 1;
                return -EINVAL;
        }

        req->next = NULL;
        req->sent = 0;
        req->complete = 0;
        req->reply_len = 0;

        local_irq_save(flags);

        if (current_req != NULL) {
                last_req->next = req;
                last_req = req;
        } else {
                current_req = req;
                last_req = req;
                if (macii_state == idle)
                        macii_start();
        }

        local_irq_restore(flags);

        return 0;
}

/* Start auto-polling */
static int macii_autopoll(int devs)
{
        unsigned long flags;

        local_irq_save(flags);

        /* bit 1 == device 1, and so on. */
        autopoll_devs = (unsigned int)devs & 0xFFFE;

        if (!current_req) {
                macii_queue_poll();
                if (current_req && macii_state == idle)
                        macii_start();
        }

        local_irq_restore(flags);

        return 0;
}

/* Prod the chip without interrupts */
static void macii_poll(void)
{
        macii_interrupt(0, NULL);
}

/* Reset the bus */
static int macii_reset_bus(void)
{
        struct adb_request req;

        /* Command = 0, Address = ignored */
        adb_request(&req, NULL, ADBREQ_NOSEND, 1, ADB_BUSRESET);
        macii_send_request(&req, 1);

        /* Don't want any more requests during the Global Reset low time. */
        udelay(3000);

        return 0;
}

/* Start sending ADB packet */
static void macii_start(void)
{
        struct adb_request *req;

        req = current_req;

        /* Now send it. Be careful though, that first byte of the request
         * is actually ADB_PACKET; the real data begins at index 1!
         * And req->nbytes is the number of bytes of real data plus one.
         */

        /* Output mode */
        via[ACR] |= SR_OUT;
        /* Load data */
        via[SR] = req->data[1];
        /* set ADB state to 'command' */
        via[B] = (via[B] & ~ST_MASK) | ST_CMD;

        macii_state = sending;
        data_index = 2;

        bus_timeout = false;
        srq_asserted = false;
}

/*
 * The notorious ADB interrupt handler - does all of the protocol handling.
 * Relies on the ADB controller sending and receiving data, thereby
 * generating shift register interrupts (SR_INT) for us. This means there has
 * to be activity on the ADB bus. The chip will poll to achieve this.
 *
 * The VIA Port B output signalling works as follows. After the ADB transceiver
 * sees a transition on the PB4 and PB5 lines it will crank over the VIA shift
 * register which eventually raises the SR_INT interrupt. The PB4/PB5 outputs
 * are toggled with each byte as the ADB transaction progresses.
 *
 * Request with no reply expected (and empty transceiver buffer):
 *     CMD -> IDLE
 * Request with expected reply packet (or with buffered autopoll packet):
 *     CMD -> EVEN -> ODD -> EVEN -> ... -> IDLE
 * Unsolicited packet:
 *     IDLE -> EVEN -> ODD -> EVEN -> ... -> IDLE
 */
static irqreturn_t macii_interrupt(int irq, void *arg)
{
        int x;
        struct adb_request *req;
        unsigned long flags;

        local_irq_save(flags);

        if (!arg) {
                /* Clear the SR IRQ flag when polling. */
                if (via[IFR] & SR_INT)
                        via[IFR] = SR_INT;
                else {
                        local_irq_restore(flags);
                        return IRQ_NONE;
                }
        }

        status = via[B] & (ST_MASK | CTLR_IRQ);

        switch (macii_state) {
        case idle:
                WARN_ON((status & ST_MASK) != ST_IDLE);

                reply_ptr = reply_buf;
                reading_reply = false;

                bus_timeout = false;
                srq_asserted = false;

                x = via[SR];

                if (!(status & CTLR_IRQ)) {
                        /* /CTLR_IRQ asserted in idle state means we must
                         * read an autopoll reply from the transceiver buffer.
                         */
                        macii_state = reading;
                        *reply_ptr = x;
                        reply_len = 1;
                } else {
                        /* bus timeout */
                        reply_len = 0;
                        break;
                }

                /* set ADB state = even for first data byte */
                via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
                break;

        case sending:
                req = current_req;

                if (status == (ST_CMD | CTLR_IRQ)) {
                        /* /CTLR_IRQ de-asserted after the command byte means
                         * the host can continue with the transaction.
                         */

                        /* Store command byte */
                        last_cmd = req->data[1];
                        if ((last_cmd & OP_MASK) == TALK) {
                                last_talk_cmd = last_cmd;
                                if ((last_cmd & CMD_MASK) == ADB_READREG(0, 0))
                                        last_poll_cmd = last_cmd;
                        }
                }

                if (status == ST_CMD) {
                        /* /CTLR_IRQ asserted after the command byte means we
                         * must read an autopoll reply. The first byte was
                         * lost because the shift register was an output.
                         */
                        macii_state = reading;

                        reading_reply = false;
                        reply_ptr = reply_buf;
                        *reply_ptr = last_talk_cmd;
                        reply_len = 1;

                        /* reset to shift in */
                        via[ACR] &= ~SR_OUT;
                        x = via[SR];
                } else if (data_index >= req->nbytes) {
                        req->sent = 1;

                        if (req->reply_expected) {
                                macii_state = reading;

                                reading_reply = true;
                                reply_ptr = req->reply;
                                *reply_ptr = req->data[1];
                                reply_len = 1;

                                via[ACR] &= ~SR_OUT;
                                x = via[SR];
                        } else if ((req->data[1] & OP_MASK) == TALK) {
                                macii_state = reading;

                                reading_reply = false;
                                reply_ptr = reply_buf;
                                *reply_ptr = req->data[1];
                                reply_len = 1;

                                via[ACR] &= ~SR_OUT;
                                x = via[SR];

                                req->complete = 1;
                                current_req = req->next;
                                if (req->done)
                                        (*req->done)(req);
                        } else {
                                macii_state = idle;

                                req->complete = 1;
                                current_req = req->next;
                                if (req->done)
                                        (*req->done)(req);
                                break;
                        }
                } else {
                        via[SR] = req->data[data_index++];
                }

                if ((via[B] & ST_MASK) == ST_CMD) {
                        /* just sent the command byte, set to EVEN */
                        via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
                } else {
                        /* invert state bits, toggle ODD/EVEN */
                        via[B] ^= ST_MASK;
                }
                break;

        case reading:
                x = via[SR];
                WARN_ON((status & ST_MASK) == ST_CMD ||
                        (status & ST_MASK) == ST_IDLE);

                if (!(status & CTLR_IRQ)) {
                        if (status == ST_EVEN && reply_len == 1) {
                                bus_timeout = true;
                        } else if (status == ST_ODD && reply_len == 2) {
                                srq_asserted = true;
                        } else {
                                macii_state = idle;

                                if (bus_timeout)
                                        reply_len = 0;

                                if (reading_reply) {
                                        struct adb_request *req = current_req;

                                        req->reply_len = reply_len;

                                        req->complete = 1;
                                        current_req = req->next;
                                        if (req->done)
                                                (*req->done)(req);
                                } else if (reply_len && autopoll_devs &&
                                           reply_buf[0] == last_poll_cmd) {
                                        adb_input(reply_buf, reply_len, 1);
                                }
                                break;
                        }
                }

                if (reply_len < ARRAY_SIZE(reply_buf)) {
                        reply_ptr++;
                        *reply_ptr = x;
                        reply_len++;
                }

                /* invert state bits, toggle ODD/EVEN */
                via[B] ^= ST_MASK;
                break;

        default:
                break;
        }

        if (macii_state == idle) {
                if (!current_req)
                        macii_queue_poll();

                if (current_req)
                        macii_start();

                if (macii_state == idle) {
                        via[ACR] &= ~SR_OUT;
                        x = via[SR];
                        via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
                }
        }

        local_irq_restore(flags);
        return IRQ_HANDLED;
}