atari_ncr5380.c

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/*
 * NCR 5380 generic driver routines.  These should make it *trivial*
 *	to implement 5380 SCSI drivers under Linux with a non-trantor
 *	architecture.
 *
 *	Note that these routines also work with NR53c400 family chips.
 *
 * Copyright 1993, Drew Eckhardt
 *	Visionary Computing
 *	(Unix and Linux consulting and custom programming)
 *	[e-mail]
 *	[phone]
 *
 * DISTRIBUTION RELEASE 6.
 *
 * For more information, please consult
 *
 * NCR 5380 Family
 * SCSI Protocol Controller
 * Databook
 *
 * NCR Microelectronics
 * 1635 Aeroplaza Drive
 * Colorado Springs, CO 80916
 * 1+ [phone]
 * 1+ [phone]
 */

/*
 * ++roman: To port the 5380 driver to the Atari, I had to do some changes in
 * this file, too:
 *
 *  - Some of the debug statements were incorrect (undefined variables and the
 *    like). I fixed that.
 *
 *  - In information_transfer(), I think a #ifdef was wrong. Looking at the
 *    possible DMA transfer size should also happen for REAL_DMA. I added this
 *    in the #if statement.
 *
 *  - When using real DMA, information_transfer() should return in a DATAOUT
 *    phase after starting the DMA. It has nothing more to do.
 *
 *  - The interrupt service routine should run main after end of DMA, too (not
 *    only after RESELECTION interrupts). Additionally, it should _not_ test
 *    for more interrupts after running main, since a DMA process may have
 *    been started and interrupts are turned on now. The new int could happen
 *    inside the execution of NCR5380_intr(), leading to recursive
 *    calls.
 *
 *  - I've added a function merge_contiguous_buffers() that tries to
 *    merge scatter-gather buffers that are located at contiguous
 *    physical addresses and can be processed with the same DMA setup.
 *    Since most scatter-gather operations work on a page (4K) of
 *    4 buffers (1K), in more than 90% of all cases three interrupts and
 *    DMA setup actions are saved.
 *
 * - I've deleted all the stuff for AUTOPROBE_IRQ, REAL_DMA_POLL, PSEUDO_DMA
 *    and USLEEP, because these were messing up readability and will never be
 *    needed for Atari SCSI.
 *
 * - I've revised the NCR5380_main() calling scheme (relax the 'main_running'
 *   stuff), and 'main' is executed in a bottom half if awoken by an
 *   interrupt.
 *
 * - The code was quite cluttered up by "#if (NDEBUG & NDEBUG_*) printk..."
 *   constructs. In my eyes, this made the source rather unreadable, so I
 *   finally replaced that by the *_PRINTK() macros.
 *
 */

/*
 * Further development / testing that should be done :
 * 1.  Test linked command handling code after Eric is ready with
 *     the high level code.
 */
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_transport_spi.h>

#if (NDEBUG & NDEBUG_LISTS)
#define LIST(x, y)						\
	do {							\
		printk("LINE:%d   Adding %p to %p\n",		\
		       __LINE__, (void*)(x), (void*)(y));	\
		if ((x) == (y))					\
			udelay(5);				\
	} while (0)
#define REMOVE(w, x, y, z)					\
	do {							\
		printk("LINE:%d   Removing: %p->%p  %p->%p \n",	\
		       __LINE__, (void*)(w), (void*)(x),	\
		       (void*)(y), (void*)(z));			\
		if ((x) == (y))					\
			udelay(5);				\
	} while (0)
#else
#define LIST(x,y)
#define REMOVE(w,x,y,z)
#endif

#ifndef notyet
#undef LINKED
#endif

/*
 * Design
 * Issues :
 *
 * The other Linux SCSI drivers were written when Linux was Intel PC-only,
 * and specifically for each board rather than each chip.  This makes their
 * adaptation to platforms like the Mac (Some of which use NCR5380's)
 * more difficult than it has to be.
 *
 * Also, many of the SCSI drivers were written before the command queuing
 * routines were implemented, meaning their implementations of queued
 * commands were hacked on rather than designed in from the start.
 *
 * When I designed the Linux SCSI drivers I figured that
 * while having two different SCSI boards in a system might be useful
 * for debugging things, two of the same type wouldn't be used.
 * Well, I was wrong and a number of users have mailed me about running
 * multiple high-performance SCSI boards in a server.
 *
 * Finally, when I get questions from users, I have no idea what
 * revision of my driver they are running.
 *
 * This driver attempts to address these problems :
 * This is a generic 5380 driver.  To use it on a different platform,
 * one simply writes appropriate system specific macros (ie, data
 * transfer - some PC's will use the I/O bus, 68K's must use
 * memory mapped) and drops this file in their 'C' wrapper.
 *
 * As far as command queueing, two queues are maintained for
 * each 5380 in the system - commands that haven't been issued yet,
 * and commands that are currently executing.  This means that an
 * unlimited number of commands may be queued, letting
 * more commands propagate from the higher driver levels giving higher
 * throughput.  Note that both I_T_L and I_T_L_Q nexuses are supported,
 * allowing multiple commands to propagate all the way to a SCSI-II device
 * while a command is already executing.
 *
 * To solve the multiple-boards-in-the-same-system problem,
 * there is a separate instance structure for each instance
 * of a 5380 in the system.  So, multiple NCR5380 drivers will
 * be able to coexist with appropriate changes to the high level
 * SCSI code.
 *
 * A NCR5380_PUBLIC_REVISION macro is provided, with the release
 * number (updated for each public release) printed by the
 * NCR5380_print_options command, which should be called from the
 * wrapper detect function, so that I know what release of the driver
 * users are using.
 *
 * Issues specific to the NCR5380 :
 *
 * When used in a PIO or pseudo-dma mode, the NCR5380 is a braindead
 * piece of hardware that requires you to sit in a loop polling for
 * the REQ signal as long as you are connected.  Some devices are
 * brain dead (ie, many TEXEL CD ROM drives) and won't disconnect
 * while doing long seek operations.
 *
 * The workaround for this is to keep track of devices that have
 * disconnected.  If the device hasn't disconnected, for commands that
 * should disconnect, we do something like
 *
 * while (!REQ is asserted) { sleep for N usecs; poll for M usecs }
 *
 * Some tweaking of N and M needs to be done.  An algorithm based
 * on "time to data" would give the best results as long as short time
 * to datas (ie, on the same track) were considered, however these
 * broken devices are the exception rather than the rule and I'd rather
 * spend my time optimizing for the normal case.
 *
 * Architecture :
 *
 * At the heart of the design is a coroutine, NCR5380_main,
 * which is started when not running by the interrupt handler,
 * timer, and queue command function.  It attempts to establish
 * I_T_L or I_T_L_Q nexuses by removing the commands from the
 * issue queue and calling NCR5380_select() if a nexus
 * is not established.
 *
 * Once a nexus is established, the NCR5380_information_transfer()
 * phase goes through the various phases as instructed by the target.
 * if the target goes into MSG IN and sends a DISCONNECT message,
 * the command structure is placed into the per instance disconnected
 * queue, and NCR5380_main tries to find more work.  If USLEEP
 * was defined, and the target is idle for too long, the system
 * will try to sleep.
 *
 * If a command has disconnected, eventually an interrupt will trigger,
 * calling NCR5380_intr()  which will in turn call NCR5380_reselect
 * to reestablish a nexus.  This will run main if necessary.
 *
 * On command termination, the done function will be called as
 * appropriate.
 *
 * SCSI pointers are maintained in the SCp field of SCSI command
 * structures, being initialized after the command is connected
 * in NCR5380_select, and set as appropriate in NCR5380_information_transfer.
 * Note that in violation of the standard, an implicit SAVE POINTERS operation
 * is done, since some BROKEN disks fail to issue an explicit SAVE POINTERS.
 */

/*
 * Using this file :
 * This file a skeleton Linux SCSI driver for the NCR 5380 series
 * of chips.  To use it, you write an architecture specific functions
 * and macros and include this file in your driver.
 *
 * These macros control options :
 * AUTOSENSE - if defined, REQUEST SENSE will be performed automatically
 *	for commands that return with a CHECK CONDITION status.
 *
 * LINKED - if defined, linked commands are supported.
 *
 * REAL_DMA - if defined, REAL DMA is used during the data transfer phases.
 *
 * SUPPORT_TAGS - if defined, SCSI-2 tagged queuing is used where possible
 *
 * These macros MUST be defined :
 *
 * NCR5380_read(register)  - read from the specified register
 *
 * NCR5380_write(register, value) - write to the specific register
 *
 * Either real DMA *or* pseudo DMA may be implemented
 * REAL functions :
 * NCR5380_REAL_DMA should be defined if real DMA is to be used.
 * Note that the DMA setup functions should return the number of bytes
 *	that they were able to program the controller for.
 *
 * Also note that generic i386/PC versions of these macros are
 *	available as NCR5380_i386_dma_write_setup,
 *	NCR5380_i386_dma_read_setup, and NCR5380_i386_dma_residual.
 *
 * NCR5380_dma_write_setup(instance, src, count) - initialize
 * NCR5380_dma_read_setup(instance, dst, count) - initialize
 * NCR5380_dma_residual(instance); - residual count
 *
 * PSEUDO functions :
 * NCR5380_pwrite(instance, src, count)
 * NCR5380_pread(instance, dst, count);
 *
 * If nothing specific to this implementation needs doing (ie, with external
 * hardware), you must also define
 *
 * NCR5380_queue_command
 * NCR5380_reset
 * NCR5380_abort
 * NCR5380_proc_info
 *
 * to be the global entry points into the specific driver, ie
 * #define NCR5380_queue_command t128_queue_command.
 *
 * If this is not done, the routines will be defined as static functions
 * with the NCR5380* names and the user must provide a globally
 * accessible wrapper function.
 *
 * The generic driver is initialized by calling NCR5380_init(instance),
 * after setting the appropriate host specific fields and ID.  If the
 * driver wishes to autoprobe for an IRQ line, the NCR5380_probe_irq(instance,
 * possible) function may be used.  Before the specific driver initialization
 * code finishes, NCR5380_print_options should be called.
 */

static struct Scsi_Host *first_instance = NULL;
static struct scsi_host_template *the_template = NULL;

/* Macros ease life... :-) */
#define	SETUP_HOSTDATA(in)				\
    struct NCR5380_hostdata *hostdata =			\
	(struct NCR5380_hostdata *)(in)->hostdata
#define	HOSTDATA(in) ((struct NCR5380_hostdata *)(in)->hostdata)

#define	NEXT(cmd)		((Scsi_Cmnd *)(cmd)->host_scribble)
#define	SET_NEXT(cmd,next)	((cmd)->host_scribble = (void *)(next))
#define	NEXTADDR(cmd)		((Scsi_Cmnd **)&(cmd)->host_scribble)

#define	HOSTNO		instance->host_no
#define	H_NO(cmd)	(cmd)->device->host->host_no

#ifdef SUPPORT_TAGS

/*
 * Functions for handling tagged queuing
 * =====================================
 *
 * ++roman (01/96): Now I've implemented SCSI-2 tagged queuing. Some notes:
 *
 * Using consecutive numbers for the tags is no good idea in my eyes. There
 * could be wrong re-usings if the counter (8 bit!) wraps and some early
 * command has been preempted for a long time. My solution: a bitfield for
 * remembering used tags.
 *
 * There's also the problem that each target has a certain queue size, but we
 * cannot know it in advance :-( We just see a QUEUE_FULL status being
 * returned. So, in this case, the driver internal queue size assumption is
 * reduced to the number of active tags if QUEUE_FULL is returned by the
 * target. The command is returned to the mid-level, but with status changed
 * to BUSY, since --as I've seen-- the mid-level can't handle QUEUE_FULL
 * correctly.
 *
 * We're also not allowed running tagged commands as long as an untagged
 * command is active. And REQUEST SENSE commands after a contingent allegiance
 * condition _must_ be untagged. To keep track whether an untagged command has
 * been issued, the host->busy array is still employed, as it is without
 * support for tagged queuing.
 *
 * One could suspect that there are possible race conditions between
 * is_lun_busy(), cmd_get_tag() and cmd_free_tag(). But I think this isn't the
 * case: is_lun_busy() and cmd_get_tag() are both called from NCR5380_main(),
 * which already guaranteed to be running at most once. It is also the only
 * place where tags/LUNs are allocated. So no other allocation can slip
 * between that pair, there could only happen a reselection, which can free a
 * tag, but that doesn't hurt. Only the sequence in cmd_free_tag() becomes
 * important: the tag bit must be cleared before 'nr_allocated' is decreased.
 */

/* -1 for TAG_NONE is not possible with unsigned char cmd->tag */
#undef TAG_NONE
#define TAG_NONE 0xff

typedef struct {
	DECLARE_BITMAP(allocated, MAX_TAGS);
	int nr_allocated;
	int queue_size;
} TAG_ALLOC;

static TAG_ALLOC TagAlloc[8][8];	/* 8 targets and 8 LUNs */


static void __init init_tags(void)
{
	int target, lun;
	TAG_ALLOC *ta;

	if (!setup_use_tagged_queuing)
		return;

	for (target = 0; target < 8; ++target) {
		for (lun = 0; lun < 8; ++lun) {
			ta = &TagAlloc[target][lun];
			bitmap_zero(ta->allocated, MAX_TAGS);
			ta->nr_allocated = 0;
			/* At the beginning, assume the maximum queue size we could
			 * support (MAX_TAGS). This value will be decreased if the target
			 * returns QUEUE_FULL status.
			 */
			ta->queue_size = MAX_TAGS;
		}
	}
}


/* Check if we can issue a command to this LUN: First see if the LUN is marked
 * busy by an untagged command. If the command should use tagged queuing, also
 * check that there is a free tag and the target's queue won't overflow. This
 * function should be called with interrupts disabled to avoid race
 * conditions.
 */

static int is_lun_busy(Scsi_Cmnd *cmd, int should_be_tagged)
{
	SETUP_HOSTDATA(cmd->device->host);

	if (hostdata->busy[cmd->device->id] & (1 << cmd->device->lun))
		return 1;
	if (!should_be_tagged ||
	    !setup_use_tagged_queuing || !cmd->device->tagged_supported)
		return 0;
	if (TagAlloc[cmd->device->id][cmd->device->lun].nr_allocated >=
	    TagAlloc[cmd->device->id][cmd->device->lun].queue_size) {
		TAG_PRINTK("scsi%d: target %d lun %d: no free tags\n",
			   H_NO(cmd), cmd->device->id, cmd->device->lun);
		return 1;
	}
	return 0;
}


/* Allocate a tag for a command (there are no checks anymore, check_lun_busy()
 * must be called before!), or reserve the LUN in 'busy' if the command is
 * untagged.
 */

static void cmd_get_tag(Scsi_Cmnd *cmd, int should_be_tagged)
{
	SETUP_HOSTDATA(cmd->device->host);

	/* If we or the target don't support tagged queuing, allocate the LUN for
	 * an untagged command.
	 */
	if (!should_be_tagged ||
	    !setup_use_tagged_queuing || !cmd->device->tagged_supported) {
		cmd->tag = TAG_NONE;
		hostdata->busy[cmd->device->id] |= (1 << cmd->device->lun);
		TAG_PRINTK("scsi%d: target %d lun %d now allocated by untagged "
			   "command\n", H_NO(cmd), cmd->device->id, cmd->device->lun);
	} else {
		TAG_ALLOC *ta = &TagAlloc[cmd->device->id][cmd->device->lun];

		cmd->tag = find_first_zero_bit(ta->allocated, MAX_TAGS);
		set_bit(cmd->tag, ta->allocated);
		ta->nr_allocated++;
		TAG_PRINTK("scsi%d: using tag %d for target %d lun %d "
			   "(now %d tags in use)\n",
			   H_NO(cmd), cmd->tag, cmd->device->id,
			   cmd->device->lun, ta->nr_allocated);
	}
}


/* Mark the tag of command 'cmd' as free, or in case of an untagged command,
 * unlock the LUN.
 */

static void cmd_free_tag(Scsi_Cmnd *cmd)
{
	SETUP_HOSTDATA(cmd->device->host);

	if (cmd->tag == TAG_NONE) {
		hostdata->busy[cmd->device->id] &= ~(1 << cmd->device->lun);
		TAG_PRINTK("scsi%d: target %d lun %d untagged cmd finished\n",
			   H_NO(cmd), cmd->device->id, cmd->device->lun);
	} else if (cmd->tag >= MAX_TAGS) {
		printk(KERN_NOTICE "scsi%d: trying to free bad tag %d!\n",
		       H_NO(cmd), cmd->tag);