drivers/ide/ide-timing.h

#ifndef _IDE_TIMING_H
#define _IDE_TIMING_H

/*
 *  Copyright (c) 1999-2001 Vojtech Pavlik
 */

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Should you need to contact me, the author, you can do so either by
 * e-mail - mail your message to <vojtech@ucw.cz>, or by paper mail:
 * Vojtech Pavlik, Simunkova 1594, Prague 8, 182 00 Czech Republic
 */

#include <linux/kernel.h>
#include <linux/hdreg.h>

/*
 * PIO 0-5, MWDMA 0-2 and UDMA 0-6 timings (in nanoseconds).
 * These were taken from ATA/ATAPI-6 standard, rev 0a, except
 * for PIO 5, which is a nonstandard extension and UDMA6, which
 * is currently supported only by Maxtor drives. 
 */

static struct ide_timing ide_timing[] = {

	{ XFER_UDMA_6,     0,   0,   0,   0,   0,   0,   0,  15 },
	{ XFER_UDMA_5,     0,   0,   0,   0,   0,   0,   0,  20 },
	{ XFER_UDMA_4,     0,   0,   0,   0,   0,   0,   0,  30 },
	{ XFER_UDMA_3,     0,   0,   0,   0,   0,   0,   0,  45 },

	{ XFER_UDMA_2,     0,   0,   0,   0,   0,   0,   0,  60 },
	{ XFER_UDMA_1,     0,   0,   0,   0,   0,   0,   0,  80 },
	{ XFER_UDMA_0,     0,   0,   0,   0,   0,   0,   0, 120 },

	{ XFER_MW_DMA_2,  25,   0,   0,   0,  70,  25, 120,   0 },
	{ XFER_MW_DMA_1,  45,   0,   0,   0,  80,  50, 150,   0 },
	{ XFER_MW_DMA_0,  60,   0,   0,   0, 215, 215, 480,   0 },

	{ XFER_SW_DMA_2,  60,   0,   0,   0, 120, 120, 240,   0 },
	{ XFER_SW_DMA_1,  90,   0,   0,   0, 240, 240, 480,   0 },
	{ XFER_SW_DMA_0, 120,   0,   0,   0, 480, 480, 960,   0 },

	{ XFER_PIO_5,     20,  50,  30, 100,  50,  30, 100,   0 },
	{ XFER_PIO_4,     25,  70,  25, 120,  70,  25, 120,   0 },
	{ XFER_PIO_3,     30,  80,  70, 180,  80,  70, 180,   0 },

	{ XFER_PIO_2,     30, 290,  40, 330, 100,  90, 240,   0 },
	{ XFER_PIO_1,     50, 290,  93, 383, 125, 100, 383,   0 },
	{ XFER_PIO_0,     70, 290, 240, 600, 165, 150, 600,   0 },

	{ XFER_PIO_SLOW, 120, 290, 240, 960, 290, 240, 960,   0 },

	{ 0xff }
};

#define ENOUGH(v,unit)		(((v)-1)/(unit)+1)
#define EZ(v,unit)		((v)?ENOUGH(v,unit):0)

static void ide_timing_quantize(struct ide_timing *t, struct ide_timing *q, int T, int UT)
{
	q->setup   = EZ(t->setup   * 1000,  T);
	q->act8b   = EZ(t->act8b   * 1000,  T);
	q->rec8b   = EZ(t->rec8b   * 1000,  T);
	q->cyc8b   = EZ(t->cyc8b   * 1000,  T);
	q->active  = EZ(t->active  * 1000,  T);
	q->recover = EZ(t->recover * 1000,  T);
	q->cycle   = EZ(t->cycle   * 1000,  T);
	q->udma    = EZ(t->udma    * 1000, UT);
}

static void ide_timing_merge(struct ide_timing *a, struct ide_timing *b, struct ide_timing *m, unsigned int what)
{
	if (what & IDE_TIMING_SETUP  ) m->setup   = max(a->setup,   b->setup);
	if (what & IDE_TIMING_ACT8B  ) m->act8b   = max(a->act8b,   b->act8b);
	if (what & IDE_TIMING_REC8B  ) m->rec8b   = max(a->rec8b,   b->rec8b);
	if (what & IDE_TIMING_CYC8B  ) m->cyc8b   = max(a->cyc8b,   b->cyc8b);
	if (what & IDE_TIMING_ACTIVE ) m->active  = max(a->active,  b->active);
	if (what & IDE_TIMING_RECOVER) m->recover = max(a->recover, b->recover);
	if (what & IDE_TIMING_CYCLE  ) m->cycle   = max(a->cycle,   b->cycle);
	if (what & IDE_TIMING_UDMA   ) m->udma    = max(a->udma,    b->udma);
}

static struct ide_timing *ide_timing_find_mode(u8 speed)
{
	struct ide_timing *t;

	for (t = ide_timing; t->mode != speed; t++)
		if (t->mode == 0xff)
			return NULL;
	return t; 
}

static int ide_timing_compute(ide_drive_t *drive, u8 speed,
			      struct ide_timing *t, int T, int UT)
{
	struct hd_driveid *id = drive->id;
	struct ide_timing *s, p;

/*
 * Find the mode.
 */

	if (!(s = ide_timing_find_mode(speed)))
		return -EINVAL;

/*
 * Copy the timing from the table.
 */

	*t = *s;

/*
 * If the drive is an EIDE drive, it can tell us it needs extended
 * PIO/MWDMA cycle timing.
 */

	if (id && id->field_valid & 2) {	/* EIDE drive */

		memset(&p, 0, sizeof(p));

		if (speed <= XFER_PIO_2)
			p.cycle = p.cyc8b = id->eide_pio;
		else if (speed <= XFER_PIO_5)
			p.cycle = p.cyc8b = id->eide_pio_iordy;
		else if (speed >= XFER_MW_DMA_0 && speed <= XFER_MW_DMA_2)
			p.cycle = id->eide_dma_min;

		ide_timing_merge(&p, t, t, IDE_TIMING_CYCLE | IDE_TIMING_CYC8B);
	}

/*
 * Convert the timing to bus clock counts.
 */

	ide_timing_quantize(t, t, T, UT);

/*
 * Even in DMA/UDMA modes we still use PIO access for IDENTIFY, S.M.A.R.T
 * and some other commands. We have to ensure that the DMA cycle timing is
 * slower/equal than the fastest PIO timing.
 */

	if (speed >= XFER_SW_DMA_0) {
		u8 pio = ide_get_best_pio_mode(drive, 255, 5);
		ide_timing_compute(drive, XFER_PIO_0 + pio, &p, T, UT);
		ide_timing_merge(&p, t, t, IDE_TIMING_ALL);
	}

/*
 * Lengthen active & recovery time so that cycle time is correct.
 */

	if (t->act8b + t->rec8b < t->cyc8b) {
		t->act8b += (t->cyc8b - (t->act8b + t->rec8b)) / 2;
		t->rec8b = t->cyc8b - t->act8b;
	}

	if (t->active + t->recover < t->cycle) {
		t->active += (t->cycle - (t->active + t->recover)) / 2;
		t->recover = t->cycle - t->active;
	}

	return 0;
}

#endif