horizon.c

讲述linux的初始化过程

    ;
  return;
}

/* TX */

static inline void SELECT_TX_CHANNEL (hrz_dev * dev, u16 tx_channel) {
  wr_regl (dev, TX_CHANNEL_PORT_OFF, tx_channel);
  return;
}

/* Update or query one configuration parameter of a particular channel. */

static inline void update_tx_channel_config (hrz_dev * dev, short chan, u8 mode, u16 value) {
  wr_regw (dev, TX_CHANNEL_CONFIG_COMMAND_OFF,
	   chan * TX_CHANNEL_CONFIG_MULT | mode);
    wr_regw (dev, TX_CHANNEL_CONFIG_DATA_OFF, value);
    return;
}

static inline u16 query_tx_channel_config (hrz_dev * dev, short chan, u8 mode) {
  wr_regw (dev, TX_CHANNEL_CONFIG_COMMAND_OFF,
	   chan * TX_CHANNEL_CONFIG_MULT | mode);
    return rd_regw (dev, TX_CHANNEL_CONFIG_DATA_OFF);
}

/********** dump functions **********/

static inline void dump_skb (char * prefix, unsigned int vc, struct sk_buff * skb) {
#ifdef DEBUG_HORIZON
  unsigned int i;
  unsigned char * data = skb->data;
  PRINTDB (DBG_DATA, "%s(%u) ", prefix, vc);
  for (i=0; i<skb->len && i < 256;i++)
    PRINTDM (DBG_DATA, "%02x ", data[i]);
  PRINTDE (DBG_DATA,"");
#else
  (void) prefix;
  (void) vc;
  (void) skb;
#endif
  return;
}

static inline void dump_regs (hrz_dev * dev) {
#ifdef DEBUG_HORIZON
  PRINTD (DBG_REGS, "CONTROL 0: %#x", rd_regl (dev, CONTROL_0_REG));
  PRINTD (DBG_REGS, "RX CONFIG: %#x", rd_regw (dev, RX_CONFIG_OFF));
  PRINTD (DBG_REGS, "TX CONFIG: %#x", rd_regw (dev, TX_CONFIG_OFF));
  PRINTD (DBG_REGS, "TX STATUS: %#x", rd_regw (dev, TX_STATUS_OFF));
  PRINTD (DBG_REGS, "IRQ ENBLE: %#x", rd_regl (dev, INT_ENABLE_REG_OFF));
  PRINTD (DBG_REGS, "IRQ SORCE: %#x", rd_regl (dev, INT_SOURCE_REG_OFF));
#else
  (void) dev;
#endif
  return;
}

static inline void dump_framer (hrz_dev * dev) {
#ifdef DEBUG_HORIZON
  unsigned int i;
  PRINTDB (DBG_REGS, "framer registers:");
  for (i = 0; i < 0x10; ++i)
    PRINTDM (DBG_REGS, " %02x", rd_framer (dev, i));
  PRINTDE (DBG_REGS,"");
#else
  (void) dev;
#endif
  return;
}

/********** VPI/VCI <-> (RX) channel conversions **********/

/* RX channels are 10 bit integers, these fns are quite paranoid */

static inline int channel_to_vpivci (const u16 channel, short * vpi, int * vci) {
  unsigned short vci_bits = 10 - vpi_bits;
  if ((channel & RX_CHANNEL_MASK) == channel) {
    *vci = channel & ((~0)<<vci_bits);
    *vpi = channel >> vci_bits;
    return channel ? 0 : -EINVAL;
  }
  return -EINVAL;
}

static inline int vpivci_to_channel (u16 * channel, const short vpi, const int vci) {
  unsigned short vci_bits = 10 - vpi_bits;
  if (0 <= vpi && vpi < 1<<vpi_bits && 0 <= vci && vci < 1<<vci_bits) {
    *channel = vpi<<vci_bits | vci;
    return *channel ? 0 : -EINVAL;
  }
  return -EINVAL;
}

/********** decode RX queue entries **********/

static inline u16 rx_q_entry_to_length (u32 x) {
  return x & RX_Q_ENTRY_LENGTH_MASK;
}

static inline u16 rx_q_entry_to_rx_channel (u32 x) {
  return (x>>RX_Q_ENTRY_CHANNEL_SHIFT) & RX_CHANNEL_MASK;
}

/* Cell Transmit Rate Values
 *
 * the cell transmit rate (cells per sec) can be set to a variety of
 * different values by specifying two parameters: a timer preload from
 * 1 to 16 (stored as 0 to 15) and a clock divider (2 to the power of
 * an exponent from 0 to 14; the special value 15 disables the timer).
 *
 * cellrate = baserate / (preload * 2^divider)
 *
 * The maximum cell rate that can be specified is therefore just the
 * base rate. Halving the preload is equivalent to adding 1 to the
 * divider and so values 1 to 8 of the preload are redundant except
 * in the case of a maximal divider (14).
 *
 * Given a desired cell rate, an algorithm to determine the preload
 * and divider is:
 * 
 * a) x = baserate / cellrate, want p * 2^d = x (as far as possible)
 * b) if x > 16 * 2^14 then set p = 16, d = 14 (min rate), done
 *    if x <= 16 then set p = x, d = 0 (high rates), done
 * c) now have 16 < x <= 2^18, or 1 < x/16 <= 2^14 and we want to
 *    know n such that 2^(n-1) < x/16 <= 2^n, so slide a bit until
 *    we find the range (n will be between 1 and 14), set d = n
 * d) Also have 8 < x/2^n <= 16, so set p nearest x/2^n
 *
 * The algorithm used below is a minor variant of the above.
 *
 * The base rate is derived from the oscillator frequency (Hz) using a
 * fixed divider:
 *
 * baserate = freq / 32 in the case of some Unknown Card
 * baserate = freq / 8  in the case of the Horizon        25
 * baserate = freq / 8  in the case of the Horizon Ultra 155
 *
 * The Horizon cards have oscillators and base rates as follows:
 *
 * Card               Oscillator  Base Rate
 * Unknown Card       33 MHz      1.03125 MHz (33 MHz = PCI freq)
 * Horizon        25  32 MHz      4       MHz
 * Horizon Ultra 155  40 MHz      5       MHz
 *
 * The following defines give the base rates in Hz. These were
 * previously a factor of 100 larger, no doubt someone was using
 * cps*100.
 */

#define BR_UKN 1031250l
#define BR_HRZ 4000000l
#define BR_ULT 5000000l

// d is an exponent
#define CR_MIND 0
#define CR_MAXD 14

// p ranges from 1 to a power of 2
#define CR_MAXPEXP 4

static int make_rate (const hrz_dev * dev, u32 c, rounding r,
		      u16 * bits, unsigned int * actual) {
  
  // note: rounding the rate down means rounding 'p' up
  
  const unsigned long br = test_bit (ultra, (hrz_flags *) &dev->flags) ?
    BR_ULT : BR_HRZ;
  
  u32 div = CR_MIND;
  u32 pre;
  
  // local fn to build the timer bits
  int set_cr (void) {
    // paranoia
    if (div > CR_MAXD || (!pre) || pre > 1<<CR_MAXPEXP) {
      PRINTD (DBG_QOS, "set_cr internal failure: d=%u p=%u",
	      div, pre);
      return -EINVAL;
    } else {
      if (bits)
	*bits = (div<<CLOCK_SELECT_SHIFT) | (pre-1);
      if (actual) {
	*actual = (br + (pre<<div) - 1) / (pre<<div);
	PRINTD (DBG_QOS, "actual rate: %u", *actual);
      }
      return 0;
    }
  }
  
  // br_exp and br_man are used to avoid overflowing (c*maxp*2^d) in
  // the tests below. We could think harder about exact possibilities
  // of failure...
  
  unsigned long br_man = br;
  unsigned int br_exp = 0;
  
  PRINTD (DBG_QOS|DBG_FLOW, "make_rate b=%lu, c=%u, %s", br, c,
	  (r == round_up) ? "up" : (r == round_down) ? "down" : "nearest");
  
  // avoid div by zero
  if (!c) {
    PRINTD (DBG_QOS|DBG_ERR, "zero rate is not allowed!");
    return -EINVAL;
  }
  
  while (br_exp < CR_MAXPEXP + CR_MIND && (br_man % 2 == 0)) {
    br_man = br_man >> 1;
    ++br_exp;
  }
  // (br >>br_exp) <<br_exp == br and
  // br_exp <= CR_MAXPEXP+CR_MIND
  
  if (br_man <= (c << (CR_MAXPEXP+CR_MIND-br_exp))) {
    // Equivalent to: B <= (c << (MAXPEXP+MIND))
    // take care of rounding
    switch (r) {
      case round_down:
	pre = (br+(c<<div)-1)/(c<<div);
	// but p must be non-zero
	if (!pre)
	  pre = 1;
	break;
      case round_nearest:
	pre = (br+(c<<div)/2)/(c<<div);
	// but p must be non-zero
	if (!pre)
	  pre = 1;
	break;
      case round_up:
	pre = br/(c<<div);
	// but p must be non-zero
	if (!pre)
	  return -EINVAL;
	break;
    }
    PRINTD (DBG_QOS, "A: p=%u, d=%u", pre, div);
    return set_cr ();
  }
  
  // at this point we have
  // d == MIND and (c << (MAXPEXP+MIND)) < B
  while (div < CR_MAXD) {
    div++;
    if (br_man <= (c << (CR_MAXPEXP+div-br_exp))) {
      // Equivalent to: B <= (c << (MAXPEXP+d))
      // c << (MAXPEXP+d-1) < B <= c << (MAXPEXP+d)
      // 1 << (MAXPEXP-1) < B/2^d/c <= 1 << MAXPEXP
      // MAXP/2 < B/c2^d <= MAXP
      // take care of rounding
      switch (r) {
	case round_down:
	  pre = (br+(c<<div)-1)/(c<<div);
	  break;
	case round_nearest:
	  pre = (br+(c<<div)/2)/(c<<div);
	  break;
	case round_up:
	  pre = br/(c<<div);
	  break;
      }
      PRINTD (DBG_QOS, "B: p=%u, d=%u", pre, div);
      return set_cr ();
    }
  }
  // at this point we have
  // d == MAXD and (c << (MAXPEXP+MAXD)) < B
  // but we cannot go any higher
  // take care of rounding
  switch (r) {
    case round_down:
      return -EINVAL;
      break;
    case round_nearest:
      break;
    case round_up:
      break;
  }
  pre = 1 << CR_MAXPEXP;
  PRINTD (DBG_QOS, "C: p=%u, d=%u", pre, div);
  return set_cr ();
}

static int make_rate_with_tolerance (const hrz_dev * dev, u32 c, rounding r, unsigned int tol,
				     u16 * bit_pattern, unsigned int * actual) {
  unsigned int my_actual;
  
  PRINTD (DBG_QOS|DBG_FLOW, "make_rate_with_tolerance c=%u, %s, tol=%u",
	  c, (r == round_up) ? "up" : (r == round_down) ? "down" : "nearest", tol);
  
  if (!actual)
    // actual rate is not returned
    actual = &my_actual;
  
  if (make_rate (dev, c, round_nearest, bit_pattern, actual))
    // should never happen as round_nearest always succeeds
    return -1;
  
  if (c - tol <= *actual && *actual <= c + tol)
    // within tolerance
    return 0;
  else
    // intolerant, try rounding instead
    return make_rate (dev, c, r, bit_pattern, actual);
}

/********** Listen on a VC **********/

static int hrz_open_rx (hrz_dev * dev, u16 channel) {
  // is there any guarantee that we don't get two simulataneous
  // identical calls of this function from different processes? yes
  // rate_lock
  unsigned long flags;
  u32 channel_type; // u16?
  
  u16 buf_ptr = RX_CHANNEL_IDLE;
  
  rx_ch_desc * rx_desc = &memmap->rx_descs[channel];
  
  PRINTD (DBG_FLOW, "hrz_open_rx %x", channel);
  
  spin_lock_irqsave (&dev->mem_lock, flags);
  channel_type = rd_mem (dev, &rx_desc->wr_buf_type) & BUFFER_PTR_MASK;
  spin_unlock_irqrestore (&dev->mem_lock, flags);
  
  // very serious error, should never occur
  if (channel_type != RX_CHANNEL_DISABLED) {
    PRINTD (DBG_ERR|DBG_VCC, "RX channel for VC already open");
    return -EBUSY; // clean up?
  }
  
  // Give back spare buffer
  if (dev->noof_spare_buffers) {
    buf_ptr = dev->spare_buffers[--dev->noof_spare_buffers];
    PRINTD (DBG_VCC, "using a spare buffer: %u", buf_ptr);
    // should never occur
    if (buf_ptr == RX_CHANNEL_DISABLED || buf_ptr == RX_CHANNEL_IDLE) {
      // but easy to recover from
      PRINTD (DBG_ERR|DBG_VCC, "bad spare buffer pointer, using IDLE");
      buf_ptr = RX_CHANNEL_IDLE;
    }
  } else {
    PRINTD (DBG_VCC, "using IDLE buffer pointer");
  }
  
  // Channel is currently disabled so change its status to idle
  
  // do we really need to save the flags again?
  spin_lock_irqsave (&dev->mem_lock, flags);
  
  wr_mem (dev, &rx_desc->wr_buf_type,
	  buf_ptr | CHANNEL_TYPE_AAL5 | FIRST_CELL_OF_AAL5_FRAME);
  if (buf_ptr != RX_CHANNEL_IDLE)
    wr_mem (dev, &rx_desc->rd_buf_type, buf_ptr);
  
  spin_unlock_irqrestore (&dev->mem_lock, flags);
  
  // rxer->rate = make_rate (qos->peak_cells);
  
  PRINTD (DBG_FLOW, "hrz_open_rx ok");
  
  return 0;
}

#if 0
/********** change vc rate for a given vc **********/

static void hrz_change_vc_qos (ATM_RXER * rxer, MAAL_QOS * qos) {
  rxer->rate = make_rate (qos->peak_cells);
}
#endif

/********** free an skb (as per ATM device driver documentation) **********/

static inline void hrz_kfree_skb (struct sk_buff * skb) {
  if (ATM_SKB(skb)->vcc->pop) {
    ATM_SKB(skb)->vcc->pop (ATM_SKB(skb)->vcc, skb);
  } else {
    dev_kfree_skb_any (skb);
  }
}

/********** cancel listen on a VC **********/

static void hrz_close_rx (hrz_dev * dev, u16 vc) {
  unsigned long flags;
  
  u32 value;
  
  u32 r1, r2;
  
  rx_ch_desc * rx_desc = &memmap->rx_descs[vc];
  
  int was_idle = 0;
  
  spin_lock_irqsave (&dev->mem_lock, flags);
  value = rd_mem (dev, &rx_desc->wr_buf_type) & BUFFER_PTR_MASK;
  spin_unlock_irqrestore (&dev->mem_lock, flags);
  
  if (value == RX_CHANNEL_DISABLED) {
    // I suppose this could happen once we deal with _NONE traffic properly
    PRINTD (DBG_VCC, "closing VC: RX channel %u already disabled", vc);
    return;
  }
  if (value == RX_CHANNEL_IDLE)
    was_idle = 1;
  
  spin_lock_irqsave (&dev->mem_lock, flags);
  
  for (;;) {
    wr_mem (dev, &rx_desc->wr_buf_type, RX_CHANNEL_DISABLED);
    
    if ((rd_mem (dev, &rx_desc->wr_buf_type) & BUFFER_PTR_MASK) == RX_CHANNEL_DISABLED)
      break;
    
    was_idle = 0;
  }
  
  if (was_idle) {
    spin_unlock_irqrestore (&dev->mem_lock, flags);
    return;
  }
  
  WAIT_FLUSH_RX_COMPLETE(dev);
  
  // XXX Is this all really necessary? We can rely on the rx_data_av
  // handler to discard frames that remain queued for delivery. If the
  // worry is that immediately reopening the channel (perhaps by a
  // different process) may cause some data to be mis-delivered then
  // there may still be a simpler solution (such as busy-waiting on
  // rx_busy once the channel is disabled or before a new one is
  // opened - does this leave any holes?). Arguably setting up and
  // tearing down the TX and RX halves of each virtual circuit could
  // most safely be done within ?x_busy protected regions.
  
  // OK, current changes are that Simon's marker is disabled and we DO
  // look for NULL rxer elsewhere. The code here seems flush frames
  // and then remember the last dead cell belonging to the channel
  // just disabled - the cell gets relinked at the next vc_open.