atari_scsi.c

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/*
 * atari_scsi.c -- Device dependent functions for the Atari generic SCSI port
 *
 * Copyright 1994 Roman Hodek <[e-mail]>
 *
 *   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(CONFIG_TT_DMA_EMUL)
#include "atari_dma_emul.c"
#endif

#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\n",
	       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!\n");
	} 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!\n");
	}
}
#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\n",
		   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\n",
			       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.\n",
			   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\n",
					   512 - (atari_dma_residual & 0x1ff));
				atari_dma_residual = (atari_dma_residual + 511) & ~0x1ff;
			}
		}
		tt_scsi_dma.dma_ctrl = 0;