/*
   * atari_scsi.c -- Device dependent functions for the Atari generic SCSI port
   *
   * Copyright 1994 Roman Hodek <Roman.Hodek@informatik.uni-erlangen.de>
   *
   *   Loosely based on the work of Robert De Vries' team and added:
   *    - working real DMA
   *    - Falcon support (untested yet!)   ++bjoern fixed and now it works
   *    - lots of extensions and bug fixes.
   *
   * This file is subject to the terms and conditions of the GNU General Public
   * License.  See the file COPYING in the main directory of this archive
   * for more details.
   *
   */
  
  
  /**************************************************************************/
  /*                                                                        */
  /* Notes for Falcon SCSI:                                                 */
  /* ----------------------                                                 */
  /*                                                                        */
  /* Since the Falcon SCSI uses the ST-DMA chip, that is shared among       */
  /* several device drivers, locking and unlocking the access to this       */
  /* chip is required. But locking is not possible from an interrupt,       */
  /* since it puts the process to sleep if the lock is not available.       */
  /* This prevents "late" locking of the DMA chip, i.e. locking it just     */
  /* before using it, since in case of disconnection-reconnection           */
  /* commands, the DMA is started from the reselection interrupt.           */
  /*                                                                        */
  /* Two possible schemes for ST-DMA-locking would be:                      */
  /*  1) The lock is taken for each command separately and disconnecting    */
  /*     is forbidden (i.e. can_queue = 1).                                 */
  /*  2) The DMA chip is locked when the first command comes in and         */
  /*     released when the last command is finished and all queues are      */
  /*     empty.                                                             */
  /* The first alternative would result in bad performance, since the       */
  /* interleaving of commands would not be used. The second is unfair to    */
  /* other drivers using the ST-DMA, because the queues will seldom be      */
  /* totally empty if there is a lot of disk traffic.                       */
  /*                                                                        */
  /* For this reasons I decided to employ a more elaborate scheme:          */
  /*  - First, we give up the lock every time we can (for fairness), this    */
  /*    means every time a command finishes and there are no other commands */
  /*    on the disconnected queue.                                          */
  /*  - If there are others waiting to lock the DMA chip, we stop           */
  /*    issuing commands, i.e. moving them onto the issue queue.           */
  /*    Because of that, the disconnected queue will run empty in a         */
  /*    while. Instead we go to sleep on a 'fairness_queue'.                */
  /*  - If the lock is released, all processes waiting on the fairness      */
  /*    queue will be woken. The first of them tries to re-lock the DMA,     */
  /*    the others wait for the first to finish this task. After that,      */
  /*    they can all run on and do their commands...                        */
  /* This sounds complicated (and it is it :-(), but it seems to be a       */
  /* good compromise between fairness and performance: As long as no one     */
  /* else wants to work with the ST-DMA chip, SCSI can go along as          */
  /* usual. If now someone else comes, this behaviour is changed to a       */
  /* "fairness mode": just already initiated commands are finished and      */
  /* then the lock is released. The other one waiting will probably win     */
  /* the race for locking the DMA, since it was waiting for longer. And     */
  /* after it has finished, SCSI can go ahead again. Finally: I hope I      */
  /* have not produced any deadlock possibilities!                          */
  /*                                                                        */
  /**************************************************************************/

  #include <linux/module.h>
  
  #define NDEBUG (0)

  #define NDEBUG_ABORT		0x00100000
  #define NDEBUG_TAGS		0x00200000
  #define NDEBUG_MERGING		0x00400000

  
  #define AUTOSENSE
  /* For the Atari version, use only polled IO or REAL_DMA */
  #define	REAL_DMA
  /* Support tagged queuing? (on devices that are able to... :-) */
  #define	SUPPORT_TAGS
  #define	MAX_TAGS 32
  
  #include <linux/types.h>
  #include <linux/stddef.h>
  #include <linux/ctype.h>
  #include <linux/delay.h>
  #include <linux/mm.h>
  #include <linux/blkdev.h>

  #include <linux/interrupt.h>
  #include <linux/init.h>
  #include <linux/nvram.h>
  #include <linux/bitops.h>
  
  #include <asm/setup.h>
  #include <asm/atarihw.h>
  #include <asm/atariints.h>
  #include <asm/page.h>
  #include <asm/pgtable.h>
  #include <asm/irq.h>
  #include <asm/traps.h>
  
  #include "scsi.h"
  #include <scsi/scsi_host.h>
  #include "atari_scsi.h"
  #include "NCR5380.h"
  #include <asm/atari_stdma.h>
  #include <asm/atari_stram.h>
  #include <asm/io.h>
  
  #include <linux/stat.h>
  
  #define	IS_A_TT()	ATARIHW_PRESENT(TT_SCSI)
  
  #define	SCSI_DMA_WRITE_P(elt,val)				\
  	do {							\
  		unsigned long v = val;				\
  		tt_scsi_dma.elt##_lo = v & 0xff;		\
  		v >>= 8;					\
  		tt_scsi_dma.elt##_lmd = v & 0xff;		\
  		v >>= 8;					\
  		tt_scsi_dma.elt##_hmd = v & 0xff;		\
  		v >>= 8;					\
  		tt_scsi_dma.elt##_hi = v & 0xff;		\
  	} while(0)
  
  #define	SCSI_DMA_READ_P(elt)					\
  	(((((((unsigned long)tt_scsi_dma.elt##_hi << 8) |	\
  	     (unsigned long)tt_scsi_dma.elt##_hmd) << 8) |	\
  	   (unsigned long)tt_scsi_dma.elt##_lmd) << 8) |	\
  	 (unsigned long)tt_scsi_dma.elt##_lo)
  
  
  static inline void SCSI_DMA_SETADR(unsigned long adr)
  {
  	st_dma.dma_lo = (unsigned char)adr;
  	MFPDELAY();
  	adr >>= 8;
  	st_dma.dma_md = (unsigned char)adr;
  	MFPDELAY();
  	adr >>= 8;
  	st_dma.dma_hi = (unsigned char)adr;
  	MFPDELAY();
  }
  
  static inline unsigned long SCSI_DMA_GETADR(void)
  {
  	unsigned long adr;
  	adr = st_dma.dma_lo;
  	MFPDELAY();
  	adr |= (st_dma.dma_md & 0xff) << 8;
  	MFPDELAY();
  	adr |= (st_dma.dma_hi & 0xff) << 16;
  	MFPDELAY();
  	return adr;
  }
  
  static inline void ENABLE_IRQ(void)
  {
  	if (IS_A_TT())
  		atari_enable_irq(IRQ_TT_MFP_SCSI);
  	else
  		atari_enable_irq(IRQ_MFP_FSCSI);
  }
  
  static inline void DISABLE_IRQ(void)
  {
  	if (IS_A_TT())
  		atari_disable_irq(IRQ_TT_MFP_SCSI);
  	else
  		atari_disable_irq(IRQ_MFP_FSCSI);
  }
  
  
  #define HOSTDATA_DMALEN		(((struct NCR5380_hostdata *) \
  				(atari_scsi_host->hostdata))->dma_len)
  
  /* Time (in jiffies) to wait after a reset; the SCSI standard calls for 250ms,
   * we usually do 0.5s to be on the safe side. But Toshiba CD-ROMs once more
   * need ten times the standard value... */
  #ifndef CONFIG_ATARI_SCSI_TOSHIBA_DELAY
  #define	AFTER_RESET_DELAY	(HZ/2)
  #else
  #define	AFTER_RESET_DELAY	(5*HZ/2)
  #endif
  
  /***************************** Prototypes *****************************/
  
  #ifdef REAL_DMA

  static int scsi_dma_is_ignored_buserr(unsigned char dma_stat);
  static void atari_scsi_fetch_restbytes(void);
  static long atari_scsi_dma_residual(struct Scsi_Host *instance);
  static int falcon_classify_cmd(Scsi_Cmnd *cmd);
  static unsigned long atari_dma_xfer_len(unsigned long wanted_len,
  					Scsi_Cmnd *cmd, int write_flag);

  #endif

  static irqreturn_t scsi_tt_intr(int irq, void *dummy);
  static irqreturn_t scsi_falcon_intr(int irq, void *dummy);
  static void falcon_release_lock_if_possible(struct NCR5380_hostdata *hostdata);
  static void falcon_get_lock(void);

  #ifdef CONFIG_ATARI_SCSI_RESET_BOOT

  static void atari_scsi_reset_boot(void);

  #endif

  static unsigned char atari_scsi_tt_reg_read(unsigned char reg);
  static void atari_scsi_tt_reg_write(unsigned char reg, unsigned char value);
  static unsigned char atari_scsi_falcon_reg_read(unsigned char reg);
  static void atari_scsi_falcon_reg_write(unsigned char reg, unsigned char value);

  
  /************************* End of Prototypes **************************/

  static struct Scsi_Host *atari_scsi_host;
  static unsigned char (*atari_scsi_reg_read)(unsigned char reg);
  static void (*atari_scsi_reg_write)(unsigned char reg, unsigned char value);

  
  #ifdef REAL_DMA
  static unsigned long	atari_dma_residual, atari_dma_startaddr;
  static short		atari_dma_active;
  /* pointer to the dribble buffer */

  static char		*atari_dma_buffer;

  /* precalculated physical address of the dribble buffer */
  static unsigned long	atari_dma_phys_buffer;
  /* != 0 tells the Falcon int handler to copy data from the dribble buffer */
  static char		*atari_dma_orig_addr;
  /* size of the dribble buffer; 4k seems enough, since the Falcon cannot use
   * scatter-gather anyway, so most transfers are 1024 byte only. In the rare
   * cases where requests to physical contiguous buffers have been merged, this
   * request is <= 4k (one page). So I don't think we have to split transfers
   * just due to this buffer size...
   */
  #define	STRAM_BUFFER_SIZE	(4096)
  /* mask for address bits that can't be used with the ST-DMA */
  static unsigned long	atari_dma_stram_mask;
  #define STRAM_ADDR(a)	(((a) & atari_dma_stram_mask) == 0)
  /* number of bytes to cut from a transfer to handle NCR overruns */

  static int atari_read_overruns;

  #endif
  
  static int setup_can_queue = -1;

  module_param(setup_can_queue, int, 0);

  static int setup_cmd_per_lun = -1;

  module_param(setup_cmd_per_lun, int, 0);

  static int setup_sg_tablesize = -1;

  module_param(setup_sg_tablesize, int, 0);

  #ifdef SUPPORT_TAGS
  static int setup_use_tagged_queuing = -1;

  module_param(setup_use_tagged_queuing, int, 0);

  #endif
  static int setup_hostid = -1;

  module_param(setup_hostid, int, 0);

  #if defined(REAL_DMA)

  static int scsi_dma_is_ignored_buserr(unsigned char dma_stat)

  {
  	int i;

  	unsigned long addr = SCSI_DMA_READ_P(dma_addr), end_addr;

  
  	if (dma_stat & 0x01) {
  
  		/* A bus error happens when DMA-ing from the last page of a
  		 * physical memory chunk (DMA prefetch!), but that doesn't hurt.
  		 * Check for this case:
  		 */

  
  		for (i = 0; i < m68k_num_memory; ++i) {
  			end_addr = m68k_memory[i].addr + m68k_memory[i].size;

  			if (end_addr <= addr && addr <= end_addr + 4)

  				return 1;

  		}
  	}

  	return 0;

  }
  
  
  #if 0
  /* Dead code... wasn't called anyway :-) and causes some trouble, because at
   * end-of-DMA, both SCSI ints are triggered simultaneously, so the NCR int has
   * to clear the DMA int pending bit before it allows other level 6 interrupts.
   */

  static void scsi_dma_buserr(int irq, void *dummy)

  {

  	unsigned char dma_stat = tt_scsi_dma.dma_ctrl;

  
  	/* Don't do anything if a NCR interrupt is pending. Probably it's just
  	 * masked... */

  	if (atari_irq_pending(IRQ_TT_MFP_SCSI))

  		return;

  	printk("Bad SCSI DMA interrupt! dma_addr=0x%08lx dma_stat=%02x dma_cnt=%08lx
  ",
  	       SCSI_DMA_READ_P(dma_addr), dma_stat, SCSI_DMA_READ_P(dma_cnt));
  	if (dma_stat & 0x80) {

  		if (!scsi_dma_is_ignored_buserr(dma_stat))
  			printk("SCSI DMA bus error -- bad DMA programming!
  ");
  	} else {

  		/* Under normal circumstances we never should get to this point,
  		 * since both interrupts are triggered simultaneously and the 5380
  		 * int has higher priority. When this irq is handled, that DMA
  		 * interrupt is cleared. So a warning message is printed here.
  		 */

  		printk("SCSI DMA intr ?? -- this shouldn't happen!
  ");

  	}
  }
  #endif
  
  #endif

  static irqreturn_t scsi_tt_intr(int irq, void *dummy)

  {
  #ifdef REAL_DMA
  	int dma_stat;
  
  	dma_stat = tt_scsi_dma.dma_ctrl;
  
  	INT_PRINTK("scsi%d: NCR5380 interrupt, DMA status = %02x
  ",
  		   atari_scsi_host->host_no, dma_stat & 0xff);
  
  	/* Look if it was the DMA that has interrupted: First possibility
  	 * is that a bus error occurred...
  	 */
  	if (dma_stat & 0x80) {

  		if (!scsi_dma_is_ignored_buserr(dma_stat)) {

  			printk(KERN_ERR "SCSI DMA caused bus error near 0x%08lx
  ",
  			       SCSI_DMA_READ_P(dma_addr));
  			printk(KERN_CRIT "SCSI DMA bus error -- bad DMA programming!");
  		}
  	}
  
  	/* If the DMA is active but not finished, we have the case
  	 * that some other 5380 interrupt occurred within the DMA transfer.
  	 * This means we have residual bytes, if the desired end address
  	 * is not yet reached. Maybe we have to fetch some bytes from the
  	 * rest data register, too. The residual must be calculated from
  	 * the address pointer, not the counter register, because only the
  	 * addr reg counts bytes not yet written and pending in the rest
  	 * data reg!
  	 */
  	if ((dma_stat & 0x02) && !(dma_stat & 0x40)) {

  		atari_dma_residual = HOSTDATA_DMALEN - (SCSI_DMA_READ_P(dma_addr) - atari_dma_startaddr);

  
  		DMA_PRINTK("SCSI DMA: There are %ld residual bytes.
  ",
  			   atari_dma_residual);
  
  		if ((signed int)atari_dma_residual < 0)
  			atari_dma_residual = 0;
  		if ((dma_stat & 1) == 0) {

  			/*
  			 * After read operations, we maybe have to
  			 * transport some rest bytes
  			 */

  			atari_scsi_fetch_restbytes();

  		} else {
  			/*
  			 * There seems to be a nasty bug in some SCSI-DMA/NCR
  			 * combinations: If a target disconnects while a write
  			 * operation is going on, the address register of the
  			 * DMA may be a few bytes farer than it actually read.
  			 * This is probably due to DMA prefetching and a delay
  			 * between DMA and NCR.  Experiments showed that the
  			 * dma_addr is 9 bytes to high, but this could vary.
  			 * The problem is, that the residual is thus calculated
  			 * wrong and the next transfer will start behind where
  			 * it should.  So we round up the residual to the next
  			 * multiple of a sector size, if it isn't already a
  			 * multiple and the originally expected transfer size
  			 * was.  The latter condition is there to ensure that
  			 * the correction is taken only for "real" data
  			 * transfers and not for, e.g., the parameters of some
  			 * other command.  These shouldn't disconnect anyway.
  			 */

  			if (atari_dma_residual & 0x1ff) {
  				DMA_PRINTK("SCSI DMA: DMA bug corrected, "
  					   "difference %ld bytes
  ",
  					   512 - (atari_dma_residual & 0x1ff));
  				atari_dma_residual = (atari_dma_residual + 511) & ~0x1ff;
  			}
  		}
  		tt_scsi_dma.dma_ctrl = 0;
  	}
  
  	/* If the DMA is finished, fetch the rest bytes and turn it off */
  	if (dma_stat & 0x40) {
  		atari_dma_residual = 0;
  		if ((dma_stat & 1) == 0)
  			atari_scsi_fetch_restbytes();
  		tt_scsi_dma.dma_ctrl = 0;
  	}
  
  #endif /* REAL_DMA */

  	NCR5380_intr(irq, dummy);

  
  #if 0
  	/* To be sure the int is not masked */

  	atari_enable_irq(IRQ_TT_MFP_SCSI);

  #endif
  	return IRQ_HANDLED;
  }

  static irqreturn_t scsi_falcon_intr(int irq, void *dummy)

  {
  #ifdef REAL_DMA
  	int dma_stat;
  
  	/* Turn off DMA and select sector counter register before
  	 * accessing the status register (Atari recommendation!)
  	 */
  	st_dma.dma_mode_status = 0x90;
  	dma_stat = st_dma.dma_mode_status;
  
  	/* Bit 0 indicates some error in the DMA process... don't know
  	 * what happened exactly (no further docu).
  	 */
  	if (!(dma_stat & 0x01)) {
  		/* DMA error */
  		printk(KERN_CRIT "SCSI DMA error near 0x%08lx!
  ", SCSI_DMA_GETADR());
  	}
  
  	/* If the DMA was active, but now bit 1 is not clear, it is some
  	 * other 5380 interrupt that finishes the DMA transfer. We have to
  	 * calculate the number of residual bytes and give a warning if
  	 * bytes are stuck in the ST-DMA fifo (there's no way to reach them!)
  	 */
  	if (atari_dma_active && (dma_stat & 0x02)) {

  		unsigned long transferred;

  
  		transferred = SCSI_DMA_GETADR() - atari_dma_startaddr;
  		/* The ST-DMA address is incremented in 2-byte steps, but the
  		 * data are written only in 16-byte chunks. If the number of
  		 * transferred bytes is not divisible by 16, the remainder is
  		 * lost somewhere in outer space.
  		 */
  		if (transferred & 15)
  			printk(KERN_ERR "SCSI DMA error: %ld bytes lost in "
  			       "ST-DMA fifo
  ", transferred & 15);
  
  		atari_dma_residual = HOSTDATA_DMALEN - transferred;
  		DMA_PRINTK("SCSI DMA: There are %ld residual bytes.
  ",
  			   atari_dma_residual);

  	} else

  		atari_dma_residual = 0;
  	atari_dma_active = 0;
  
  	if (atari_dma_orig_addr) {
  		/* If the dribble buffer was used on a read operation, copy the DMA-ed
  		 * data to the original destination address.
  		 */
  		memcpy(atari_dma_orig_addr, phys_to_virt(atari_dma_startaddr),
  		       HOSTDATA_DMALEN - atari_dma_residual);
  		atari_dma_orig_addr = NULL;
  	}
  
  #endif /* REAL_DMA */

  	NCR5380_intr(irq, dummy);

  	return IRQ_HANDLED;
  }
  
  
  #ifdef REAL_DMA

  static void atari_scsi_fetch_restbytes(void)

  {
  	int nr;
  	char *src, *dst;
  	unsigned long phys_dst;
  
  	/* fetch rest bytes in the DMA register */
  	phys_dst = SCSI_DMA_READ_P(dma_addr);
  	nr = phys_dst & 3;
  	if (nr) {
  		/* there are 'nr' bytes left for the last long address
  		   before the DMA pointer */
  		phys_dst ^= nr;
  		DMA_PRINTK("SCSI DMA: there are %d rest bytes for phys addr 0x%08lx",
  			   nr, phys_dst);
  		/* The content of the DMA pointer is a physical address!  */
  		dst = phys_to_virt(phys_dst);
  		DMA_PRINTK(" = virt addr %p
  ", dst);
  		for (src = (char *)&tt_scsi_dma.dma_restdata; nr != 0; --nr)
  			*dst++ = *src++;
  	}
  }
  #endif /* REAL_DMA */
  
  
  static int falcon_got_lock = 0;
  static DECLARE_WAIT_QUEUE_HEAD(falcon_fairness_wait);
  static int falcon_trying_lock = 0;
  static DECLARE_WAIT_QUEUE_HEAD(falcon_try_wait);
  static int falcon_dont_release = 0;
  
  /* This function releases the lock on the DMA chip if there is no
   * connected command and the disconnected queue is empty. On
   * releasing, instances of falcon_get_lock are awoken, that put
   * themselves to sleep for fairness. They can now try to get the lock
   * again (but others waiting longer more probably will win).
   */

  static void falcon_release_lock_if_possible(struct NCR5380_hostdata *hostdata)

  {
  	unsigned long flags;

  
  	if (IS_A_TT())
  		return;

  	local_irq_save(flags);

  	if (falcon_got_lock && !hostdata->disconnected_queue &&
  	    !hostdata->issue_queue && !hostdata->connected) {

  
  		if (falcon_dont_release) {
  #if 0
  			printk("WARNING: Lock release not allowed. Ignored
  ");
  #endif
  			local_irq_restore(flags);
  			return;
  		}
  		falcon_got_lock = 0;
  		stdma_release();

  		wake_up(&falcon_fairness_wait);

  	}
  
  	local_irq_restore(flags);
  }
  
  /* This function manages the locking of the ST-DMA.
   * If the DMA isn't locked already for SCSI, it tries to lock it by
   * calling stdma_lock(). But if the DMA is locked by the SCSI code and
   * there are other drivers waiting for the chip, we do not issue the
   * command immediately but wait on 'falcon_fairness_queue'. We will be
   * waked up when the DMA is unlocked by some SCSI interrupt. After that
   * we try to get the lock again.
   * But we must be prepared that more than one instance of
   * falcon_get_lock() is waiting on the fairness queue. They should not
   * try all at once to call stdma_lock(), one is enough! For that, the
   * first one sets 'falcon_trying_lock', others that see that variable
   * set wait on the queue 'falcon_try_wait'.
   * Complicated, complicated.... Sigh...
   */

  static void falcon_get_lock(void)

  {
  	unsigned long flags;

  	if (IS_A_TT())
  		return;

  
  	local_irq_save(flags);

  	while (!in_irq() && falcon_got_lock && stdma_others_waiting())

  		sleep_on(&falcon_fairness_wait);

  
  	while (!falcon_got_lock) {

  		if (in_irq())

  			panic("Falcon SCSI hasn't ST-DMA lock in interrupt");

  		if (!falcon_trying_lock) {
  			falcon_trying_lock = 1;
  			stdma_lock(scsi_falcon_intr, NULL);
  			falcon_got_lock = 1;
  			falcon_trying_lock = 0;

  			wake_up(&falcon_try_wait);
  		} else {
  			sleep_on(&falcon_try_wait);

  		}

  	}

  
  	local_irq_restore(flags);
  	if (!falcon_got_lock)
  		panic("Falcon SCSI: someone stole the lock :-(
  ");
  }

  int __init atari_scsi_detect(struct scsi_host_template *host)

  {
  	static int called = 0;
  	struct Scsi_Host *instance;
  
  	if (!MACH_IS_ATARI ||
  	    (!ATARIHW_PRESENT(ST_SCSI) && !ATARIHW_PRESENT(TT_SCSI)) ||
  	    called)

  		return 0;

  
  	host->proc_name = "Atari";
  
  	atari_scsi_reg_read  = IS_A_TT() ? atari_scsi_tt_reg_read :
  					   atari_scsi_falcon_reg_read;
  	atari_scsi_reg_write = IS_A_TT() ? atari_scsi_tt_reg_write :
  					   atari_scsi_falcon_reg_write;
  
  	/* setup variables */
  	host->can_queue =
  		(setup_can_queue > 0) ? setup_can_queue :
  		IS_A_TT() ? ATARI_TT_CAN_QUEUE : ATARI_FALCON_CAN_QUEUE;
  	host->cmd_per_lun =
  		(setup_cmd_per_lun > 0) ? setup_cmd_per_lun :
  		IS_A_TT() ? ATARI_TT_CMD_PER_LUN : ATARI_FALCON_CMD_PER_LUN;
  	/* Force sg_tablesize to 0 on a Falcon! */
  	host->sg_tablesize =
  		!IS_A_TT() ? ATARI_FALCON_SG_TABLESIZE :
  		(setup_sg_tablesize >= 0) ? setup_sg_tablesize : ATARI_TT_SG_TABLESIZE;
  
  	if (setup_hostid >= 0)
  		host->this_id = setup_hostid;
  	else {
  		/* use 7 as default */
  		host->this_id = 7;
  		/* Test if a host id is set in the NVRam */
  		if (ATARIHW_PRESENT(TT_CLK) && nvram_check_checksum()) {
  			unsigned char b = nvram_read_byte( 14 );
  			/* Arbitration enabled? (for TOS) If yes, use configured host ID */
  			if (b & 0x80)
  				host->this_id = b & 7;
  		}
  	}
  
  #ifdef SUPPORT_TAGS
  	if (setup_use_tagged_queuing < 0)
  		setup_use_tagged_queuing = DEFAULT_USE_TAGGED_QUEUING;
  #endif
  #ifdef REAL_DMA
  	/* If running on a Falcon and if there's TT-Ram (i.e., more than one
  	 * memory block, since there's always ST-Ram in a Falcon), then allocate a
  	 * STRAM_BUFFER_SIZE byte dribble buffer for transfers from/to alternative
  	 * Ram.
  	 */
  	if (MACH_IS_ATARI && ATARIHW_PRESENT(ST_SCSI) &&
  	    !ATARIHW_PRESENT(EXTD_DMA) && m68k_num_memory > 1) {
  		atari_dma_buffer = atari_stram_alloc(STRAM_BUFFER_SIZE, "SCSI");
  		if (!atari_dma_buffer) {

  			printk(KERN_ERR "atari_scsi_detect: can't allocate ST-RAM "
  					"double buffer
  ");
  			return 0;

  		}

  		atari_dma_phys_buffer = virt_to_phys(atari_dma_buffer);

  		atari_dma_orig_addr = 0;
  	}
  #endif

  	instance = scsi_register(host, sizeof(struct NCR5380_hostdata));
  	if (instance == NULL) {

  		atari_stram_free(atari_dma_buffer);
  		atari_dma_buffer = 0;
  		return 0;
  	}
  	atari_scsi_host = instance;

  	/*
  	 * Set irq to 0, to avoid that the mid-level code disables our interrupt
  	 * during queue_command calls. This is completely unnecessary, and even
  	 * worse causes bad problems on the Falcon, where the int is shared with
  	 * IDE and floppy!
  	 */

         instance->irq = 0;
  
  #ifdef CONFIG_ATARI_SCSI_RESET_BOOT
  	atari_scsi_reset_boot();
  #endif

  	NCR5380_init(instance, 0);

  
  	if (IS_A_TT()) {
  
  		/* This int is actually "pseudo-slow", i.e. it acts like a slow
  		 * interrupt after having cleared the pending flag for the DMA
  		 * interrupt. */
  		if (request_irq(IRQ_TT_MFP_SCSI, scsi_tt_intr, IRQ_TYPE_SLOW,

  				 "SCSI NCR5380", instance)) {

  			printk(KERN_ERR "atari_scsi_detect: cannot allocate irq %d, aborting",IRQ_TT_MFP_SCSI);
  			scsi_unregister(atari_scsi_host);
  			atari_stram_free(atari_dma_buffer);
  			atari_dma_buffer = 0;
  			return 0;
  		}
  		tt_mfp.active_edge |= 0x80;		/* SCSI int on L->H */
  #ifdef REAL_DMA
  		tt_scsi_dma.dma_ctrl = 0;
  		atari_dma_residual = 0;

  
  		if (MACH_IS_MEDUSA) {

  			/* While the read overruns (described by Drew Eckhardt in
  			 * NCR5380.c) never happened on TTs, they do in fact on the Medusa
  			 * (This was the cause why SCSI didn't work right for so long
  			 * there.) Since handling the overruns slows down a bit, I turned
  			 * the #ifdef's into a runtime condition.
  			 *
  			 * In principle it should be sufficient to do max. 1 byte with
  			 * PIO, but there is another problem on the Medusa with the DMA
  			 * rest data register. So 'atari_read_overruns' is currently set
  			 * to 4 to avoid having transfers that aren't a multiple of 4. If
  			 * the rest data bug is fixed, this can be lowered to 1.
  			 */
  			atari_read_overruns = 4;

  		}

  #endif /*REAL_DMA*/

  	} else { /* ! IS_A_TT */

  		/* Nothing to do for the interrupt: the ST-DMA is initialized
  		 * already by atari_init_INTS()
  		 */
  
  #ifdef REAL_DMA
  		atari_dma_residual = 0;
  		atari_dma_active = 0;
  		atari_dma_stram_mask = (ATARIHW_PRESENT(EXTD_DMA) ? 0x00000000
  					: 0xff000000);
  #endif
  	}
  
  	printk(KERN_INFO "scsi%d: options CAN_QUEUE=%d CMD_PER_LUN=%d SCAT-GAT=%d "
  #ifdef SUPPORT_TAGS
  			"TAGGED-QUEUING=%s "
  #endif
  			"HOSTID=%d",
  			instance->host_no, instance->hostt->can_queue,
  			instance->hostt->cmd_per_lun,
  			instance->hostt->sg_tablesize,
  #ifdef SUPPORT_TAGS
  			setup_use_tagged_queuing ? "yes" : "no",
  #endif
  			instance->hostt->this_id );

  	NCR5380_print_options(instance);
  	printk("
  ");

  
  	called = 1;

  	return 1;

  }

  int atari_scsi_release(struct Scsi_Host *sh)

  {
  	if (IS_A_TT())

  		free_irq(IRQ_TT_MFP_SCSI, sh);

  	if (atari_dma_buffer)

  		atari_stram_free(atari_dma_buffer);

  	NCR5380_exit(sh);

  	return 1;
  }

  
  void __init atari_scsi_setup(char *str, int *ints)
  {
  	/* Format of atascsi parameter is:
  	 *   atascsi=<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  	 * Defaults depend on TT or Falcon, hostid determined at run time.
  	 * Negative values mean don't change.
  	 */

  	if (ints[0] < 1) {

  		printk("atari_scsi_setup: no arguments!
  ");

  		return;
  	}
  
  	if (ints[0] >= 1) {
  		if (ints[1] > 0)
  			/* no limits on this, just > 0 */
  			setup_can_queue = ints[1];
  	}
  	if (ints[0] >= 2) {
  		if (ints[2] > 0)
  			setup_cmd_per_lun = ints[2];
  	}
  	if (ints[0] >= 3) {
  		if (ints[3] >= 0) {
  			setup_sg_tablesize = ints[3];
  			/* Must be <= SG_ALL (255) */
  			if (setup_sg_tablesize > SG_ALL)
  				setup_sg_tablesize = SG_ALL;
  		}
  	}
  	if (ints[0] >= 4) {
  		/* Must be between 0 and 7 */
  		if (ints[4] >= 0 && ints[4] <= 7)
  			setup_hostid = ints[4];
  		else if (ints[4] > 7)

  			printk("atari_scsi_setup: invalid host ID %d !
  ", ints[4]);

  	}
  #ifdef SUPPORT_TAGS
  	if (ints[0] >= 5) {
  		if (ints[5] >= 0)
  			setup_use_tagged_queuing = !!ints[5];
  	}
  #endif
  }
  
  int atari_scsi_bus_reset(Scsi_Cmnd *cmd)
  {

  	int rv;

  	struct NCR5380_hostdata *hostdata =
  		(struct NCR5380_hostdata *)cmd->device->host->hostdata;
  
  	/* For doing the reset, SCSI interrupts must be disabled first,
  	 * since the 5380 raises its IRQ line while _RST is active and we
  	 * can't disable interrupts completely, since we need the timer.
  	 */
  	/* And abort a maybe active DMA transfer */
  	if (IS_A_TT()) {

  		atari_turnoff_irq(IRQ_TT_MFP_SCSI);

  #ifdef REAL_DMA
  		tt_scsi_dma.dma_ctrl = 0;
  #endif /* REAL_DMA */

  	} else {
  		atari_turnoff_irq(IRQ_MFP_FSCSI);

  #ifdef REAL_DMA
  		st_dma.dma_mode_status = 0x90;
  		atari_dma_active = 0;
  		atari_dma_orig_addr = NULL;
  #endif /* REAL_DMA */
  	}
  
  	rv = NCR5380_bus_reset(cmd);
  
  	/* Re-enable ints */
  	if (IS_A_TT()) {

  		atari_turnon_irq(IRQ_TT_MFP_SCSI);
  	} else {
  		atari_turnon_irq(IRQ_MFP_FSCSI);

  	}
  	if ((rv & SCSI_RESET_ACTION) == SCSI_RESET_SUCCESS)
  		falcon_release_lock_if_possible(hostdata);

  	return rv;

  }

  #ifdef CONFIG_ATARI_SCSI_RESET_BOOT
  static void __init atari_scsi_reset_boot(void)
  {
  	unsigned long end;

  	/*
  	 * Do a SCSI reset to clean up the bus during initialization. No messing
  	 * with the queues, interrupts, or locks necessary here.
  	 */

  	printk("Atari SCSI: resetting the SCSI bus...");

  
  	/* get in phase */

  	NCR5380_write(TARGET_COMMAND_REG,
  		      PHASE_SR_TO_TCR(NCR5380_read(STATUS_REG)));

  
  	/* assert RST */

  	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_RST);

  	/* The min. reset hold time is 25us, so 40us should be enough */

  	udelay(50);

  	/* reset RST and interrupt */

  	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
  	NCR5380_read(RESET_PARITY_INTERRUPT_REG);

  
  	end = jiffies + AFTER_RESET_DELAY;
  	while (time_before(jiffies, end))
  		barrier();

  	printk(" done
  ");

  }
  #endif

  const char *atari_scsi_info(struct Scsi_Host *host)

  {
  	/* atari_scsi_detect() is verbose enough... */
  	static const char string[] = "Atari native SCSI";
  	return string;
  }
  
  
  #if defined(REAL_DMA)

  unsigned long atari_scsi_dma_setup(struct Scsi_Host *instance, void *data,
  				   unsigned long count, int dir)

  {

  	unsigned long addr = virt_to_phys(data);

  
  	DMA_PRINTK("scsi%d: setting up dma, data = %p, phys = %lx, count = %ld, "
  		   "dir = %d
  ", instance->host_no, data, addr, count, dir);
  
  	if (!IS_A_TT() && !STRAM_ADDR(addr)) {
  		/* If we have a non-DMAable address on a Falcon, use the dribble
  		 * buffer; 'orig_addr' != 0 in the read case tells the interrupt
  		 * handler to copy data from the dribble buffer to the originally
  		 * wanted address.
  		 */
  		if (dir)

  			memcpy(atari_dma_buffer, data, count);

  		else
  			atari_dma_orig_addr = data;
  		addr = atari_dma_phys_buffer;
  	}

  	atari_dma_startaddr = addr;	/* Needed for calculating residual later. */

  	/* Cache cleanup stuff: On writes, push any dirty cache out before sending
  	 * it to the peripheral. (Must be done before DMA setup, since at least
  	 * the ST-DMA begins to fill internal buffers right after setup. For
  	 * reads, invalidate any cache, may be altered after DMA without CPU
  	 * knowledge.

  	 *

  	 * ++roman: For the Medusa, there's no need at all for that cache stuff,
  	 * because the hardware does bus snooping (fine!).
  	 */

  	dma_cache_maintenance(addr, count, dir);

  
  	if (count == 0)
  		printk(KERN_NOTICE "SCSI warning: DMA programmed for 0 bytes !
  ");
  
  	if (IS_A_TT()) {
  		tt_scsi_dma.dma_ctrl = dir;

  		SCSI_DMA_WRITE_P(dma_addr, addr);
  		SCSI_DMA_WRITE_P(dma_cnt, count);

  		tt_scsi_dma.dma_ctrl = dir | 2;

  	} else { /* ! IS_A_TT */

  		/* set address */

  		SCSI_DMA_SETADR(addr);

  
  		/* toggle direction bit to clear FIFO and set DMA direction */
  		dir <<= 8;
  		st_dma.dma_mode_status = 0x90 | dir;
  		st_dma.dma_mode_status = 0x90 | (dir ^ 0x100);
  		st_dma.dma_mode_status = 0x90 | dir;
  		udelay(40);
  		/* On writes, round up the transfer length to the next multiple of 512
  		 * (see also comment at atari_dma_xfer_len()). */
  		st_dma.fdc_acces_seccount = (count + (dir ? 511 : 0)) >> 9;
  		udelay(40);
  		st_dma.dma_mode_status = 0x10 | dir;
  		udelay(40);
  		/* need not restore value of dir, only boolean value is tested */
  		atari_dma_active = 1;
  	}

  	return count;

  }

  static long atari_scsi_dma_residual(struct Scsi_Host *instance)

  {

  	return atari_dma_residual;

  }
  
  
  #define	CMD_SURELY_BLOCK_MODE	0
  #define	CMD_SURELY_BYTE_MODE	1
  #define	CMD_MODE_UNKNOWN		2

  static int falcon_classify_cmd(Scsi_Cmnd *cmd)

  {
  	unsigned char opcode = cmd->cmnd[0];

  	if (opcode == READ_DEFECT_DATA || opcode == READ_LONG ||

  	    opcode == READ_BUFFER)
  		return CMD_SURELY_BYTE_MODE;

  	else if (opcode == READ_6 || opcode == READ_10 ||
  		 opcode == 0xa8 /* READ_12 */ || opcode == READ_REVERSE ||
  		 opcode == RECOVER_BUFFERED_DATA) {
  		/* In case of a sequential-access target (tape), special care is
  		 * needed here: The transfer is block-mode only if the 'fixed' bit is
  		 * set! */
  		if (cmd->device->type == TYPE_TAPE && !(cmd->cmnd[1] & 1))

  			return CMD_SURELY_BYTE_MODE;

  		else

  			return CMD_SURELY_BLOCK_MODE;
  	} else
  		return CMD_MODE_UNKNOWN;

  }
  
  
  /* This function calculates the number of bytes that can be transferred via
   * DMA. On the TT, this is arbitrary, but on the Falcon we have to use the
   * ST-DMA chip. There are only multiples of 512 bytes possible and max.
   * 255*512 bytes :-( This means also, that defining READ_OVERRUNS is not
   * possible on the Falcon, since that would require to program the DMA for
   * n*512 - atari_read_overrun bytes. But it seems that the Falcon doesn't have
   * the overrun problem, so this question is academic :-)
   */

  static unsigned long atari_dma_xfer_len(unsigned long wanted_len,
  					Scsi_Cmnd *cmd, int write_flag)

  {
  	unsigned long	possible_len, limit;

  	if (IS_A_TT())
  		/* TT SCSI DMA can transfer arbitrary #bytes */

  		return wanted_len;

  
  	/* ST DMA chip is stupid -- only multiples of 512 bytes! (and max.
  	 * 255*512 bytes, but this should be enough)
  	 *
  	 * ++roman: Aaargl! Another Falcon-SCSI problem... There are some commands
  	 * that return a number of bytes which cannot be known beforehand. In this
  	 * case, the given transfer length is an "allocation length". Now it
  	 * can happen that this allocation length is a multiple of 512 bytes and
  	 * the DMA is used. But if not n*512 bytes really arrive, some input data
  	 * will be lost in the ST-DMA's FIFO :-( Thus, we have to distinguish
  	 * between commands that do block transfers and those that do byte
  	 * transfers. But this isn't easy... there are lots of vendor specific
  	 * commands, and the user can issue any command via the
  	 * SCSI_IOCTL_SEND_COMMAND.
  	 *
  	 * The solution: We classify SCSI commands in 1) surely block-mode cmd.s,
  	 * 2) surely byte-mode cmd.s and 3) cmd.s with unknown mode. In case 1)
  	 * and 3), the thing to do is obvious: allow any number of blocks via DMA
  	 * or none. In case 2), we apply some heuristic: Byte mode is assumed if
  	 * the transfer (allocation) length is < 1024, hoping that no cmd. not
  	 * explicitly known as byte mode have such big allocation lengths...
  	 * BTW, all the discussion above applies only to reads. DMA writes are
  	 * unproblematic anyways, since the targets aborts the transfer after
  	 * receiving a sufficient number of bytes.
  	 *
  	 * Another point: If the transfer is from/to an non-ST-RAM address, we
  	 * use the dribble buffer and thus can do only STRAM_BUFFER_SIZE bytes.
  	 */
  
  	if (write_flag) {
  		/* Write operation can always use the DMA, but the transfer size must
  		 * be rounded up to the next multiple of 512 (atari_dma_setup() does
  		 * this).
  		 */
  		possible_len = wanted_len;

  	} else {

  		/* Read operations: if the wanted transfer length is not a multiple of
  		 * 512, we cannot use DMA, since the ST-DMA cannot split transfers
  		 * (no interrupt on DMA finished!)
  		 */
  		if (wanted_len & 0x1ff)
  			possible_len = 0;
  		else {
  			/* Now classify the command (see above) and decide whether it is
  			 * allowed to do DMA at all */

  			switch (falcon_classify_cmd(cmd)) {
  			case CMD_SURELY_BLOCK_MODE:

  				possible_len = wanted_len;
  				break;

  			case CMD_SURELY_BYTE_MODE:

  				possible_len = 0; /* DMA prohibited */
  				break;

  			case CMD_MODE_UNKNOWN:
  			default:

  				/* For unknown commands assume block transfers if the transfer
  				 * size/allocation length is >= 1024 */
  				possible_len = (wanted_len < 1024) ? 0 : wanted_len;
  				break;
  			}
  		}
  	}

  	/* Last step: apply the hard limit on DMA transfers */

  	limit = (atari_dma_buffer && !STRAM_ADDR(virt_to_phys(cmd->SCp.ptr))) ?

  		    STRAM_BUFFER_SIZE : 255*512;
  	if (possible_len > limit)
  		possible_len = limit;
  
  	if (possible_len != wanted_len)
  		DMA_PRINTK("Sorry, must cut DMA transfer size to %ld bytes "
  			   "instead of %ld
  ", possible_len, wanted_len);

  	return possible_len;

  }
  
  
  #endif	/* REAL_DMA */
  
  
  /* NCR5380 register access functions
   *
   * There are separate functions for TT and Falcon, because the access
   * methods are quite different. The calling macros NCR5380_read and
   * NCR5380_write call these functions via function pointers.
   */

  static unsigned char atari_scsi_tt_reg_read(unsigned char reg)

  {

  	return tt_scsi_regp[reg * 2];

  }

  static void atari_scsi_tt_reg_write(unsigned char reg, unsigned char value)

  {
  	tt_scsi_regp[reg * 2] = value;
  }

  static unsigned char atari_scsi_falcon_reg_read(unsigned char reg)

  {
  	dma_wd.dma_mode_status= (u_short)(0x88 + reg);

  	return (u_char)dma_wd.fdc_acces_seccount;

  }

  static void atari_scsi_falcon_reg_write(unsigned char reg, unsigned char value)

  {
  	dma_wd.dma_mode_status = (u_short)(0x88 + reg);
  	dma_wd.fdc_acces_seccount = (u_short)value;
  }
  
  
  #include "atari_NCR5380.c"

  static struct scsi_host_template driver_template = {

  	.proc_info		= atari_scsi_proc_info,
  	.name			= "Atari native SCSI",
  	.detect			= atari_scsi_detect,
  	.release		= atari_scsi_release,
  	.info			= atari_scsi_info,
  	.queuecommand		= atari_scsi_queue_command,
  	.eh_abort_handler	= atari_scsi_abort,
  	.eh_bus_reset_handler	= atari_scsi_bus_reset,
  	.can_queue		= 0, /* initialized at run-time */
  	.this_id		= 0, /* initialized at run-time */
  	.sg_tablesize		= 0, /* initialized at run-time */
  	.cmd_per_lun		= 0, /* initialized at run-time */
  	.use_clustering		= DISABLE_CLUSTERING
  };
  
  
  #include "scsi_module.c"
  
  MODULE_LICENSE("GPL");