// SPDX-License-Identifier: GPL-2.0
/*
 * Device driver for the Cuda and Egret system controllers found on PowerMacs
 * and 68k Macs.
 *
 * The Cuda or Egret is a 6805 microcontroller interfaced to the 6522 VIA.
 * This MCU controls system power, Parameter RAM, Real Time Clock and the
 * Apple Desktop Bus (ADB) that connects to the keyboard and mouse.
 *
 * Copyright (C) 1996 Paul Mackerras.
 */
#include <linux/stdarg.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/adb.h>
#include <linux/cuda.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>

#ifdef CONFIG_PPC
#include <asm/machdep.h>
#include <asm/pmac_feature.h>
#else
#include <asm/macintosh.h>
#include <asm/macints.h>
#include <asm/mac_via.h>
#endif
#include <asm/io.h>
#include <linux/init.h>

static volatile unsigned char __iomem *via;
static DEFINE_SPINLOCK(cuda_lock);

/* 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 */

/*
 * When the Cuda design replaced the Egret, some signal names and
 * logic sense changed. They all serve the same purposes, however.
 *
 *   VIA pin       |  Egret pin
 * ----------------+------------------------------------------
 *   PB3 (input)   |  Transceiver session   (active low)
 *   PB4 (output)  |  VIA full              (active high)
 *   PB5 (output)  |  System session        (active high)
 *
 *   VIA pin       |  Cuda pin
 * ----------------+------------------------------------------
 *   PB3 (input)   |  Transfer request      (active low)
 *   PB4 (output)  |  Byte acknowledge      (active low)
 *   PB5 (output)  |  Transfer in progress  (active low)
 */

/* Bits in Port B data register */
#define TREQ            0x08            /* Transfer request */
#define TACK            0x10            /* Transfer acknowledge */
#define TIP             0x20            /* Transfer in progress */

/* 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 */

/* Duration of byte acknowledgement pulse (us) */
#define EGRET_TACK_ASSERTED_DELAY       300
#define EGRET_TACK_NEGATED_DELAY        400

/* Interval from interrupt to start of session (us) */
#define EGRET_SESSION_DELAY             450

#ifdef CONFIG_PPC
#define mcu_is_egret    false
#else
static bool mcu_is_egret;
#endif

static inline bool TREQ_asserted(u8 portb)
{
        return !(portb & TREQ);
}

static inline void assert_TIP(void)
{
        if (mcu_is_egret) {
                udelay(EGRET_SESSION_DELAY);
                out_8(&via[B], in_8(&via[B]) | TIP);
        } else
                out_8(&via[B], in_8(&via[B]) & ~TIP);
}

static inline void assert_TIP_and_TACK(void)
{
        if (mcu_is_egret) {
                udelay(EGRET_SESSION_DELAY);
                out_8(&via[B], in_8(&via[B]) | TIP | TACK);
        } else
                out_8(&via[B], in_8(&via[B]) & ~(TIP | TACK));
}

static inline void assert_TACK(void)
{
        if (mcu_is_egret) {
                udelay(EGRET_TACK_NEGATED_DELAY);
                out_8(&via[B], in_8(&via[B]) | TACK);
        } else
                out_8(&via[B], in_8(&via[B]) & ~TACK);
}

static inline void toggle_TACK(void)
{
        out_8(&via[B], in_8(&via[B]) ^ TACK);
}

static inline void negate_TACK(void)
{
        if (mcu_is_egret) {
                udelay(EGRET_TACK_ASSERTED_DELAY);
                out_8(&via[B], in_8(&via[B]) & ~TACK);
        } else
                out_8(&via[B], in_8(&via[B]) | TACK);
}

static inline void negate_TIP_and_TACK(void)
{
        if (mcu_is_egret) {
                udelay(EGRET_TACK_ASSERTED_DELAY);
                out_8(&via[B], in_8(&via[B]) & ~(TIP | TACK));
        } else
                out_8(&via[B], in_8(&via[B]) | TIP | TACK);
}

static enum cuda_state {
    idle,
    sent_first_byte,
    sending,
    reading,
    read_done,
    awaiting_reply
} cuda_state;

static struct adb_request *current_req;
static struct adb_request *last_req;
static unsigned char cuda_rbuf[16];
static unsigned char *reply_ptr;
static int reading_reply;
static int data_index;
static int cuda_irq;
#ifdef CONFIG_PPC
static struct device_node *vias;
#endif
static int cuda_fully_inited;

#ifdef CONFIG_ADB
static int cuda_probe(void);
static int cuda_send_request(struct adb_request *req, int sync);
static int cuda_adb_autopoll(int devs);
static int cuda_reset_adb_bus(void);
#endif /* CONFIG_ADB */

static int cuda_init_via(void);
static void cuda_start(void);
static irqreturn_t cuda_interrupt(int irq, void *arg);
static void cuda_input(unsigned char *buf, int nb);
void cuda_poll(void);
static int cuda_write(struct adb_request *req);

int cuda_request(struct adb_request *req,
                 void (*done)(struct adb_request *), int nbytes, ...);

#ifdef CONFIG_ADB
struct adb_driver via_cuda_driver = {
        .name         = "CUDA",
        .probe        = cuda_probe,
        .send_request = cuda_send_request,
        .autopoll     = cuda_adb_autopoll,
        .poll         = cuda_poll,
        .reset_bus    = cuda_reset_adb_bus,
};
#endif /* CONFIG_ADB */

#ifdef CONFIG_MAC
int __init find_via_cuda(void)
{
    struct adb_request req;
    int err;

    if (macintosh_config->adb_type != MAC_ADB_CUDA &&
        macintosh_config->adb_type != MAC_ADB_EGRET)
        return 0;

    via = via1;
    cuda_state = idle;
    mcu_is_egret = macintosh_config->adb_type == MAC_ADB_EGRET;

    err = cuda_init_via();
    if (err) {
        printk(KERN_ERR "cuda_init_via() failed\n");
        via = NULL;
        return 0;
    }

    /* enable autopoll */
    cuda_request(&req, NULL, 3, CUDA_PACKET, CUDA_AUTOPOLL, 1);
    while (!req.complete)
        cuda_poll();

    return 1;
}
#else
int __init find_via_cuda(void)
{
    struct adb_request req;
    struct resource res;
    int err;

    if (vias)
        return 1;
    vias = of_find_node_by_name(NULL, "via-cuda");
    if (!vias)
        return 0;

    err = of_address_to_resource(vias, 0, &res);
    if (err) {
            printk(KERN_ERR "via-cuda: Error getting \"reg\" property !\n");
            goto fail;
    }
    via = ioremap(res.start, 0x2000);
    if (via == NULL) {
            printk(KERN_ERR "via-cuda: Can't map address !\n");
            goto fail;
    }

    cuda_state = idle;
    sys_ctrler = SYS_CTRLER_CUDA;

    err = cuda_init_via();
    if (err) {
        printk(KERN_ERR "cuda_init_via() failed\n");
        via = NULL;
        return 0;
    }

    /* Clear and enable interrupts, but only on PPC. On 68K it's done  */
    /* for us by the main VIA driver in arch/m68k/mac/via.c        */

    out_8(&via[IFR], 0x7f);     /* clear interrupts by writing 1s */
    out_8(&via[IER], IER_SET|SR_INT); /* enable interrupt from SR */

    /* enable autopoll */
    cuda_request(&req, NULL, 3, CUDA_PACKET, CUDA_AUTOPOLL, 1);
    while (!req.complete)
        cuda_poll();

    return 1;

 fail:
    of_node_put(vias);
    vias = NULL;
    return 0;
}
#endif /* !defined CONFIG_MAC */

static int __init via_cuda_start(void)
{
    if (via == NULL)
        return -ENODEV;

#ifdef CONFIG_MAC
    cuda_irq = IRQ_MAC_ADB;
#else
    cuda_irq = irq_of_parse_and_map(vias, 0);
    if (!cuda_irq) {
        printk(KERN_ERR "via-cuda: can't map interrupts for %pOF\n",
               vias);
        return -ENODEV;
    }
#endif

    if (request_irq(cuda_irq, cuda_interrupt, 0, "ADB", cuda_interrupt)) {
        printk(KERN_ERR "via-cuda: can't request irq %d\n", cuda_irq);
        return -EAGAIN;
    }

    pr_info("Macintosh Cuda and Egret driver.\n");

    cuda_fully_inited = 1;
    return 0;
}

device_initcall(via_cuda_start);

#ifdef CONFIG_ADB
static int
cuda_probe(void)
{
#ifdef CONFIG_PPC
    if (sys_ctrler != SYS_CTRLER_CUDA)
        return -ENODEV;
#else
    if (macintosh_config->adb_type != MAC_ADB_CUDA &&
        macintosh_config->adb_type != MAC_ADB_EGRET)
        return -ENODEV;
#endif
    if (via == NULL)
        return -ENODEV;
    return 0;
}
#endif /* CONFIG_ADB */

static int __init sync_egret(void)
{
        if (TREQ_asserted(in_8(&via[B]))) {
                /* Complete the inbound transfer */
                assert_TIP_and_TACK();
                while (1) {
                        negate_TACK();
                        mdelay(1);
                        (void)in_8(&via[SR]);
                        assert_TACK();
                        if (!TREQ_asserted(in_8(&via[B])))
                                break;
                }
                negate_TIP_and_TACK();
        } else if (in_8(&via[B]) & TIP) {
                /* Terminate the outbound transfer */
                negate_TACK();
                assert_TACK();
                mdelay(1);
                negate_TIP_and_TACK();
        }
        /* Clear shift register interrupt */
        if (in_8(&via[IFR]) & SR_INT)
                (void)in_8(&via[SR]);
        return 0;
}

#define WAIT_FOR(cond, what)                                    \
    do {                                                        \
        int x;                                                  \
        for (x = 1000; !(cond); --x) {                          \
            if (x == 0) {                                       \
                pr_err("Timeout waiting for " what "\n");       \
                return -ENXIO;                                  \
            }                                                   \
            udelay(100);                                        \
        }                                                       \
    } while (0)

static int
__init cuda_init_via(void)
{
#ifdef CONFIG_PPC
    out_8(&via[IER], 0x7f);                                     /* disable interrupts from VIA */
    (void)in_8(&via[IER]);
#else
    out_8(&via[IER], SR_INT);                                   /* disable SR interrupt from VIA */
#endif

    out_8(&via[DIRB], (in_8(&via[DIRB]) | TACK | TIP) & ~TREQ); /* TACK & TIP out */
    out_8(&via[ACR], (in_8(&via[ACR]) & ~SR_CTRL) | SR_EXT);    /* SR data in */
    (void)in_8(&via[SR]);                                       /* clear any left-over data */

    if (mcu_is_egret)
        return sync_egret();

    negate_TIP_and_TACK();

    /* delay 4ms and then clear any pending interrupt */
    mdelay(4);
    (void)in_8(&via[SR]);
    out_8(&via[IFR], SR_INT);

    /* sync with the CUDA - assert TACK without TIP */
    assert_TACK();

    /* wait for the CUDA to assert TREQ in response */
    WAIT_FOR(TREQ_asserted(in_8(&via[B])), "CUDA response to sync");

    /* wait for the interrupt and then clear it */
    WAIT_FOR(in_8(&via[IFR]) & SR_INT, "CUDA response to sync (2)");
    (void)in_8(&via[SR]);
    out_8(&via[IFR], SR_INT);

    /* finish the sync by negating TACK */
    negate_TACK();

    /* wait for the CUDA to negate TREQ and the corresponding interrupt */
    WAIT_FOR(!TREQ_asserted(in_8(&via[B])), "CUDA response to sync (3)");
    WAIT_FOR(in_8(&via[IFR]) & SR_INT, "CUDA response to sync (4)");
    (void)in_8(&via[SR]);
    out_8(&via[IFR], SR_INT);

    return 0;
}

#ifdef CONFIG_ADB
/* Send an ADB command */
static int
cuda_send_request(struct adb_request *req, int sync)
{
    int i;

    if ((via == NULL) || !cuda_fully_inited) {
        req->complete = 1;
        return -ENXIO;
    }
  
    req->reply_expected = 1;

    i = cuda_write(req);
    if (i)
        return i;

    if (sync) {
        while (!req->complete)
            cuda_poll();
    }
    return 0;
}


/* Enable/disable autopolling */
static int
cuda_adb_autopoll(int devs)
{
    struct adb_request req;

    if ((via == NULL) || !cuda_fully_inited)
        return -ENXIO;

    cuda_request(&req, NULL, 3, CUDA_PACKET, CUDA_AUTOPOLL, (devs? 1: 0));
    while (!req.complete)
        cuda_poll();
    return 0;
}

/* Reset adb bus - how do we do this?? */
static int
cuda_reset_adb_bus(void)
{
    struct adb_request req;

    if ((via == NULL) || !cuda_fully_inited)
        return -ENXIO;

    cuda_request(&req, NULL, 2, ADB_PACKET, 0);         /* maybe? */
    while (!req.complete)
        cuda_poll();
    return 0;
}
#endif /* CONFIG_ADB */

/* Construct and send a cuda request */
int
cuda_request(struct adb_request *req, void (*done)(struct adb_request *),
             int nbytes, ...)
{
    va_list list;
    int i;

    if (via == NULL) {
        req->complete = 1;
        return -ENXIO;
    }

    req->nbytes = nbytes;
    req->done = done;
    va_start(list, nbytes);
    for (i = 0; i < nbytes; ++i)
        req->data[i] = va_arg(list, int);
    va_end(list);
    req->reply_expected = 1;
    return cuda_write(req);
}
EXPORT_SYMBOL(cuda_request);

static int
cuda_write(struct adb_request *req)
{
    unsigned long flags;

    if (req->nbytes < 2 || req->data[0] > CUDA_PACKET) {
        req->complete = 1;
        return -EINVAL;
    }
    req->next = NULL;
    req->sent = 0;
    req->complete = 0;
    req->reply_len = 0;

    spin_lock_irqsave(&cuda_lock, flags);
    if (current_req) {
        last_req->next = req;
        last_req = req;
    } else {
        current_req = req;
        last_req = req;
        if (cuda_state == idle)
            cuda_start();
    }
    spin_unlock_irqrestore(&cuda_lock, flags);

    return 0;
}

static void
cuda_start(void)
{
    /* assert cuda_state == idle */
    if (current_req == NULL)
        return;
    data_index = 0;
    if (TREQ_asserted(in_8(&via[B])))
        return;                 /* a byte is coming in from the CUDA */

    /* set the shift register to shift out and send a byte */
    out_8(&via[ACR], in_8(&via[ACR]) | SR_OUT);
    out_8(&via[SR], current_req->data[data_index++]);
    if (mcu_is_egret)
        assert_TIP_and_TACK();
    else
        assert_TIP();
    cuda_state = sent_first_byte;
}

void
cuda_poll(void)
{
        cuda_interrupt(0, NULL);
}
EXPORT_SYMBOL(cuda_poll);

#define ARRAY_FULL(a, p)        ((p) - (a) == ARRAY_SIZE(a))

static irqreturn_t
cuda_interrupt(int irq, void *arg)
{
    unsigned long flags;
    u8 status;
    struct adb_request *req = NULL;
    unsigned char ibuf[16];
    int ibuf_len = 0;
    int complete = 0;
    bool full;
    
    spin_lock_irqsave(&cuda_lock, flags);

    /* On powermacs, this handler is registered for the VIA IRQ. But they use
     * just the shift register IRQ -- other VIA interrupt sources are disabled.
     * On m68k macs, the VIA IRQ sources are dispatched individually. Unless
     * we are polling, the shift register IRQ flag has already been cleared.
     */

#ifdef CONFIG_MAC
    if (!arg)
#endif
    {
        if ((in_8(&via[IFR]) & SR_INT) == 0) {
            spin_unlock_irqrestore(&cuda_lock, flags);
            return IRQ_NONE;
        } else {
            out_8(&via[IFR], SR_INT);
        }
    }

    status = in_8(&via[B]) & (TIP | TACK | TREQ);

    switch (cuda_state) {
    case idle:
        /* System controller has unsolicited data for us */
        (void)in_8(&via[SR]);
idle_state:
        assert_TIP();
        cuda_state = reading;
        reply_ptr = cuda_rbuf;
        reading_reply = 0;
        break;

    case awaiting_reply:
        /* System controller has reply data for us */
        (void)in_8(&via[SR]);
        assert_TIP();
        cuda_state = reading;
        reply_ptr = current_req->reply;
        reading_reply = 1;
        break;

    case sent_first_byte:
        if (TREQ_asserted(status)) {
            /* collision */
            out_8(&via[ACR], in_8(&via[ACR]) & ~SR_OUT);
            (void)in_8(&via[SR]);
            negate_TIP_and_TACK();
            cuda_state = idle;
            /* Egret does not raise an "aborted" interrupt */
            if (mcu_is_egret)
                goto idle_state;
        } else {
            out_8(&via[SR], current_req->data[data_index++]);
            toggle_TACK();
            if (mcu_is_egret)
                assert_TACK();
            cuda_state = sending;
        }
        break;

    case sending:
        req = current_req;
        if (data_index >= req->nbytes) {
            out_8(&via[ACR], in_8(&via[ACR]) & ~SR_OUT);
            (void)in_8(&via[SR]);
            negate_TIP_and_TACK();
            req->sent = 1;
            if (req->reply_expected) {
                cuda_state = awaiting_reply;
            } else {
                current_req = req->next;
                complete = 1;
                /* not sure about this */
                cuda_state = idle;
                cuda_start();
            }
        } else {
            out_8(&via[SR], req->data[data_index++]);
            toggle_TACK();
            if (mcu_is_egret)
                assert_TACK();
        }
        break;

    case reading:
        full = reading_reply ? ARRAY_FULL(current_req->reply, reply_ptr)
                             : ARRAY_FULL(cuda_rbuf, reply_ptr);
        if (full)
            (void)in_8(&via[SR]);
        else
            *reply_ptr++ = in_8(&via[SR]);
        if (!TREQ_asserted(status) || full) {
            if (mcu_is_egret)
                assert_TACK();
            /* that's all folks */
            negate_TIP_and_TACK();
            cuda_state = read_done;
            /* Egret does not raise a "read done" interrupt */
            if (mcu_is_egret)
                goto read_done_state;
        } else {
            toggle_TACK();
            if (mcu_is_egret)
                negate_TACK();
        }
        break;

    case read_done:
        (void)in_8(&via[SR]);
read_done_state:
        if (reading_reply) {
            req = current_req;
            req->reply_len = reply_ptr - req->reply;
            if (req->data[0] == ADB_PACKET) {
                /* Have to adjust the reply from ADB commands */
                if (req->reply_len <= 2 || (req->reply[1] & 2) != 0) {
                    /* the 0x2 bit indicates no response */
                    req->reply_len = 0;
                } else {
                    /* leave just the command and result bytes in the reply */
                    req->reply_len -= 2;
                    memmove(req->reply, req->reply + 2, req->reply_len);
                }
            }
            current_req = req->next;
            complete = 1;
            reading_reply = 0;
        } else {
            /* This is tricky. We must break the spinlock to call
             * cuda_input. However, doing so means we might get
             * re-entered from another CPU getting an interrupt
             * or calling cuda_poll(). I ended up using the stack
             * (it's only for 16 bytes) and moving the actual
             * call to cuda_input to outside of the lock.
             */
            ibuf_len = reply_ptr - cuda_rbuf;
            memcpy(ibuf, cuda_rbuf, ibuf_len);
        }
        reply_ptr = cuda_rbuf;
        cuda_state = idle;
        cuda_start();
        if (cuda_state == idle && TREQ_asserted(in_8(&via[B]))) {
            assert_TIP();
            cuda_state = reading;
        }
        break;

    default:
        pr_err("cuda_interrupt: unknown cuda_state %d?\n", cuda_state);
    }
    spin_unlock_irqrestore(&cuda_lock, flags);
    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)
        cuda_input(ibuf, ibuf_len);
    return IRQ_HANDLED;
}

static void
cuda_input(unsigned char *buf, int nb)
{
    switch (buf[0]) {
    case ADB_PACKET:
#ifdef CONFIG_XMON
        if (nb == 5 && buf[2] == 0x2c) {
            extern int xmon_wants_key, xmon_adb_keycode;
            if (xmon_wants_key) {
                xmon_adb_keycode = buf[3];
                return;
            }
        }
#endif /* CONFIG_XMON */
#ifdef CONFIG_ADB
        adb_input(buf+2, nb-2, buf[1] & 0x40);
#endif /* CONFIG_ADB */
        break;

    case TIMER_PACKET:
        /* Egret sends these periodically. Might be useful as a 'heartbeat'
         * to trigger a recovery for the VIA shift register errata.
         */
        break;

    default:
        print_hex_dump(KERN_INFO, "cuda_input: ", DUMP_PREFIX_NONE, 32, 1,
                       buf, nb, false);
    }
}

/* Offset between Unix time (1970-based) and Mac time (1904-based) */
#define RTC_OFFSET      2082844800

time64_t cuda_get_time(void)
{
        struct adb_request req;
        u32 now;

        if (cuda_request(&req, NULL, 2, CUDA_PACKET, CUDA_GET_TIME) < 0)
                return 0;
        while (!req.complete)
                cuda_poll();
        if (req.reply_len != 7)
                pr_err("%s: got %d byte reply\n", __func__, req.reply_len);
        now = (req.reply[3] << 24) + (req.reply[4] << 16) +
              (req.reply[5] << 8) + req.reply[6];
        return (time64_t)now - RTC_OFFSET;
}

int cuda_set_rtc_time(struct rtc_time *tm)
{
        u32 now;
        struct adb_request req;

        now = lower_32_bits(rtc_tm_to_time64(tm) + RTC_OFFSET);
        if (cuda_request(&req, NULL, 6, CUDA_PACKET, CUDA_SET_TIME,
                         now >> 24, now >> 16, now >> 8, now) < 0)
                return -ENXIO;
        while (!req.complete)
                cuda_poll();
        if ((req.reply_len != 3) && (req.reply_len != 7))
                pr_err("%s: got %d byte reply\n", __func__, req.reply_len);
        return 0;
}