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via-macii.c

/*
 * 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 <fthain@telegraphics.com.au> - 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 <stdarg.h>
#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/machw.h>
#include <asm/mac_via.h>
#include <asm/system.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 */

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 = {
      "Mac II",
      macii_probe,
      macii_init,
      macii_send_request,
      macii_autopoll,
      macii_poll,
      macii_reset_bus
};

static enum macii_state {
      idle,
      sending,
      reading,
      read_done,
} 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 req->data or reply_buf */
static int 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 int last_status;              /* status bits as at previous interrupt */
static int srq_asserted;     /* have to poll for the device that asserted it */
static int command_byte;         /* the most recent command byte transmitted */
static int autopoll_devs;      /* bits set are device addresses to be polled */

/* Sanity check for request queue. Doesn't check for cycles. */
static int request_is_queued(struct adb_request *req) {
      struct adb_request *cur;
      unsigned long flags;
      local_irq_save(flags);
      cur = current_req;
      while (cur) {
            if (cur == req) {
                  local_irq_restore(flags);
                  return 1;
            }
            cur = cur->next;
      }
      local_irq_restore(flags);
      return 0;
}

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

      via = via1;

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

/* Initialize the driver */
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, IRQ_FLG_LOCK, "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;
      last_status = via[B] & (ST_MASK|CTLR_IRQ);

      /* 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)
{
      /* No point polling the active device as it will never assert SRQ, so
       * poll the next device in the autopoll list. This could leave us
       * stuck in a polling loop if an unprobed device is asserting SRQ.
       * In theory, that could only happen if a device was plugged in after
       * probing started. Unplugging it again will break the cycle.
       * (Simply polling the next higher device often ends up polling almost
       * every device (after wrapping around), which takes too long.)
       */
      int device_mask;
      int next_device;
      static struct adb_request req;

      if (!autopoll_devs) return;

      device_mask = (1 << (((command_byte & 0xF0) >> 4) + 1)) - 1;
      if (autopoll_devs & ~device_mask)
            next_device = ffs(autopoll_devs & ~device_mask) - 1;
      else
            next_device = ffs(autopoll_devs) - 1;

      BUG_ON(request_is_queued(&req));

      adb_request(&req, NULL, ADBREQ_NOSEND, 1,
                  ADB_READREG(next_device, 0));

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

      if (current_req != NULL) {
            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;
      unsigned long flags;

      BUG_ON(request_is_queued(req));

      local_irq_save(flags);
      err = macii_write(req);
      local_irq_restore(flags);

      if (!err && sync) {
            while (!req->complete) {
                  macii_poll();
            }
            BUG_ON(request_is_queued(req));
      }

      return err;
}

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

      if (current_req != NULL) {
            last_req->next = req;
            last_req = req;
      } else {
            current_req = req;
            last_req = req;
            if (macii_state == idle) macii_start();
      }
      return 0;
}

/* Start auto-polling */
static int macii_autopoll(int devs)
{
      static struct adb_request req;
      unsigned long flags;
      int err = 0;

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

      if (!autopoll_devs) return 0;

      local_irq_save(flags);

      if (current_req == NULL) {
            /* Send a Talk Reg 0. The controller will repeatedly transmit
             * this as long as it is idle.
             */
            adb_request(&req, NULL, ADBREQ_NOSEND, 1,
                        ADB_READREG(ffs(autopoll_devs) - 1, 0));
            err = macii_write(&req);
      }

      local_irq_restore(flags);
      return err;
}

static inline int need_autopoll(void) {
      /* Was the last command Talk Reg 0
       * and is the target on the autopoll list?
       */
      if ((command_byte & 0x0F) == 0x0C &&
          ((1 << ((command_byte & 0xF0) >> 4)) & autopoll_devs))
            return 0;
      return 1;
}

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

/* Reset the bus */
static int macii_reset_bus(void)
{
      static struct adb_request req;
      
      if (request_is_queued(&req))
            return 0;

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

      /* 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;

      BUG_ON(req == NULL);

      BUG_ON(macii_state != idle);

      /* 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.
       */

      /* store command byte */
      command_byte = req->data[1];
      /* 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;
}

/*
 * 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 basic ADB state machine was left unchanged from the original MacII code
 * by Alan Cox, which was based on the CUDA driver for PowerMac. 
 * The syntax of the ADB status lines is totally different on MacII,
 * though. MacII uses the states Command -> Even -> Odd -> Even ->...-> Idle
 * for sending and Idle -> Even -> Odd -> Even ->...-> Idle for receiving.
 * Start and end of a receive packet are signalled by asserting /IRQ on the
 * interrupt line (/IRQ means the CTLR_IRQ bit in port B; not to be confused
 * with the VIA shift register interrupt. /IRQ never actually interrupts the
 * processor, it's just an ordinary input.)
 */
static irqreturn_t macii_interrupt(int irq, void *arg)
{
      int x;
      static int entered;
      struct adb_request *req;

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

      BUG_ON(entered++);

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

      switch (macii_state) {
            case idle:
                  if (reading_reply) {
                        reply_ptr = current_req->reply;
                  } else {
                        BUG_ON(current_req != NULL);
                        reply_ptr = reply_buf;
                  }

                  x = via[SR];

                  if ((status & CTLR_IRQ) && (x == 0xFF)) {
                        /* Bus timeout without SRQ sequence:
                         *     data is "FF" while CTLR_IRQ is "H"
                         */
                        reply_len = 0;
                        srq_asserted = 0;
                        macii_state = read_done;
                  } else {
                        macii_state = reading;
                        *reply_ptr = x;
                        reply_len = 1;
                  }

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

            case sending:
                  req = current_req;
                  if (data_index >= req->nbytes) {
                        req->sent = 1;
                        macii_state = idle;

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

                              if (current_req)
                                    macii_start();
                              else
                                    if (need_autopoll())
                                          macii_autopoll(autopoll_devs);
                        }

                        if (macii_state == idle) {
                              /* reset to shift in */
                              via[ACR] &= ~SR_OUT;
                              x = via[SR];
                              /* set ADB state idle - might get SRQ */
                              via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
                        }
                  } 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];
                  BUG_ON((status & ST_MASK) == ST_CMD ||
                         (status & ST_MASK) == ST_IDLE);

                  /* Bus timeout with SRQ sequence:
                   *     data is "XX FF"      while CTLR_IRQ is "L L"
                   * End of packet without SRQ sequence:
                   *     data is "XX...YY 00" while CTLR_IRQ is "L...H L"
                   * End of packet SRQ sequence:
                   *     data is "XX...YY 00" while CTLR_IRQ is "L...L L"
                   * (where XX is the first response byte and
                   * YY is the last byte of valid response data.)
                   */

                  srq_asserted = 0;
                  if (!(status & CTLR_IRQ)) {
                        if (x == 0xFF) {
                              if (!(last_status & CTLR_IRQ)) {
                                    macii_state = read_done;
                                    reply_len = 0;
                                    srq_asserted = 1;
                              }
                        } else if (x == 0x00) {
                              macii_state = read_done;
                              if (!(last_status & CTLR_IRQ))
                                    srq_asserted = 1;
                        }
                  }

                  if (macii_state == reading) {
                        BUG_ON(reply_len > 15);
                        reply_ptr++;
                        *reply_ptr = x;
                        reply_len++;
                  }

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

            case read_done:
                  x = via[SR];

                  if (reading_reply) {
                        reading_reply = 0;
                        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)
                        adb_input(reply_buf, reply_len, 0);

                  macii_state = idle;

                  /* SRQ seen before, initiate poll now */
                  if (srq_asserted)
                        macii_queue_poll();

                  if (current_req)
                        macii_start();
                  else
                        if (need_autopoll())
                              macii_autopoll(autopoll_devs);

                  if (macii_state == idle)
                        via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
                  break;

            default:
            break;
      }

      entered--;
      return IRQ_HANDLED;
}

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