/*
* Copyright (C) 1999-2000 Andre Hedrick <andre@linux-ide.org>
* Copyright (C) 2002 Lionel Bouton <Lionel.Bouton@inet6.fr>, Maintainer
* Copyright (C) 2003 Vojtech Pavlik <vojtech@suse.cz>
* Copyright (C) 2007 Bartlomiej Zolnierkiewicz
*
* May be copied or modified under the terms of the GNU General Public License
*
*
* Thanks :
*
* SiS Taiwan : for direct support and hardware.
* Daniela Engert : for initial ATA100 advices and numerous others.
* John Fremlin, Manfred Spraul, Dave Morgan, Peter Kjellerstedt :
* for checking code correctness, providing patches.
*
*
* Original tests and design on the SiS620 chipset.
* ATA100 tests and design on the SiS735 chipset.
* ATA16/33 support from specs
* ATA133 support for SiS961/962 by L.C. Chang <lcchang@sis.com.tw>
* ATA133 961/962/963 fixes by Vojtech Pavlik <vojtech@suse.cz>
*
* Documentation:
* SiS chipset documentation available under NDA to companies only
* (not to individuals).
*/
/*
* The original SiS5513 comes from a SiS5511/55112/5513 chipset. The original
* SiS5513 was also used in the SiS5596/5513 chipset. Thus if we see a SiS5511
* or SiS5596, we can assume we see the first MWDMA-16 capable SiS5513 chip.
*
* Later SiS chipsets integrated the 5513 functionality into the NorthBridge,
* starting with SiS5571 and up to SiS745. The PCI ID didn't change, though. We
* can figure out that we have a more modern and more capable 5513 by looking
* for the respective NorthBridge IDs.
*
* Even later (96x family) SiS chipsets use the MuTIOL link and place the 5513
* into the SouthBrige. Here we cannot rely on looking up the NorthBridge PCI
* ID, while the now ATA-133 capable 5513 still has the same PCI ID.
* Fortunately the 5513 can be 'unmasked' by fiddling with some config space
* bits, changing its device id to the true one - 5517 for 961 and 5518 for
* 962/963.
*/
#include <linux/types.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/hdreg.h>
#include <linux/pci.h>
#include <linux/init.h>
#include <linux/ide.h>
#include "ide-timing.h"
/* registers layout and init values are chipset family dependant */
#define ATA_16 0x01
#define ATA_33 0x02
#define ATA_66 0x03
#define ATA_100a 0x04 /* SiS730/SiS550 is ATA100 with ATA66 layout */
#define ATA_100 0x05
#define ATA_133a 0x06 /* SiS961b with 133 support */
#define ATA_133 0x07 /* SiS962/963 */
static u8 chipset_family;
/*
* Devices supported
*/
static const struct {
const char *name;
u16 host_id;
u8 chipset_family;
u8 flags;
} SiSHostChipInfo[] = {
{ "SiS968", PCI_DEVICE_ID_SI_968, ATA_133 },
{ "SiS966", PCI_DEVICE_ID_SI_966, ATA_133 },
{ "SiS965", PCI_DEVICE_ID_SI_965, ATA_133 },
{ "SiS745", PCI_DEVICE_ID_SI_745, ATA_100 },
{ "SiS735", PCI_DEVICE_ID_SI_735, ATA_100 },
{ "SiS733", PCI_DEVICE_ID_SI_733, ATA_100 },
{ "SiS635", PCI_DEVICE_ID_SI_635, ATA_100 },
{ "SiS633", PCI_DEVICE_ID_SI_633, ATA_100 },
{ "SiS730", PCI_DEVICE_ID_SI_730, ATA_100a },
{ "SiS550", PCI_DEVICE_ID_SI_550, ATA_100a },
{ "SiS640", PCI_DEVICE_ID_SI_640, ATA_66 },
{ "SiS630", PCI_DEVICE_ID_SI_630, ATA_66 },
{ "SiS620", PCI_DEVICE_ID_SI_620, ATA_66 },
{ "SiS540", PCI_DEVICE_ID_SI_540, ATA_66 },
{ "SiS530", PCI_DEVICE_ID_SI_530, ATA_66 },
{ "SiS5600", PCI_DEVICE_ID_SI_5600, ATA_33 },
{ "SiS5598", PCI_DEVICE_ID_SI_5598, ATA_33 },
{ "SiS5597", PCI_DEVICE_ID_SI_5597, ATA_33 },
{ "SiS5591/2", PCI_DEVICE_ID_SI_5591, ATA_33 },
{ "SiS5582", PCI_DEVICE_ID_SI_5582, ATA_33 },
{ "SiS5581", PCI_DEVICE_ID_SI_5581, ATA_33 },
{ "SiS5596", PCI_DEVICE_ID_SI_5596, ATA_16 },
{ "SiS5571", PCI_DEVICE_ID_SI_5571, ATA_16 },
{ "SiS5517", PCI_DEVICE_ID_SI_5517, ATA_16 },
{ "SiS551x", PCI_DEVICE_ID_SI_5511, ATA_16 },
};
/* Cycle time bits and values vary across chip dma capabilities
These three arrays hold the register layout and the values to set.
Indexed by chipset_family and (dma_mode - XFER_UDMA_0) */
/* {0, ATA_16, ATA_33, ATA_66, ATA_100a, ATA_100, ATA_133} */
static u8 cycle_time_offset[] = { 0, 0, 5, 4, 4, 0, 0 };
static u8 cycle_time_range[] = { 0, 0, 2, 3, 3, 4, 4 };
static u8 cycle_time_value[][XFER_UDMA_6 - XFER_UDMA_0 + 1] = {
{ 0, 0, 0, 0, 0, 0, 0 }, /* no UDMA */
{ 0, 0, 0, 0, 0, 0, 0 }, /* no UDMA */
{ 3, 2, 1, 0, 0, 0, 0 }, /* ATA_33 */
{ 7, 5, 3, 2, 1, 0, 0 }, /* ATA_66 */
{ 7, 5, 3, 2, 1, 0, 0 }, /* ATA_100a (730 specific),
different cycle_time range and offset */
{ 11, 7, 5, 4, 2, 1, 0 }, /* ATA_100 */
{ 15, 10, 7, 5, 3, 2, 1 }, /* ATA_133a (earliest 691 southbridges) */
{ 15, 10, 7, 5, 3, 2, 1 }, /* ATA_133 */
};
/* CRC Valid Setup Time vary across IDE clock setting 33/66/100/133
See SiS962 data sheet for more detail */
static u8 cvs_time_value[][XFER_UDMA_6 - XFER_UDMA_0 + 1] = {
{ 0, 0, 0, 0, 0, 0, 0 }, /* no UDMA */
{ 0, 0, 0, 0, 0, 0, 0 }, /* no UDMA */
{ 2, 1, 1, 0, 0, 0, 0 },
{ 4, 3, 2, 1, 0, 0, 0 },
{ 4, 3, 2, 1, 0, 0, 0 },
{ 6, 4, 3, 1, 1, 1, 0 },
{ 9, 6, 4, 2, 2, 2, 2 },
{ 9, 6, 4, 2, 2, 2, 2 },
};
/* Initialize time, Active time, Recovery time vary across
IDE clock settings. These 3 arrays hold the register value
for PIO0/1/2/3/4 and DMA0/1/2 mode in order */
static u8 ini_time_value[][8] = {
{ 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 0, 0, 0, 0, 0, 0, 0 },
{ 2, 1, 0, 0, 0, 1, 0, 0 },
{ 4, 3, 1, 1, 1, 3, 1, 1 },
{ 4, 3, 1, 1, 1, 3, 1, 1 },
{ 6, 4, 2, 2, 2, 4, 2, 2 },
{ 9, 6, 3, 3, 3, 6, 3, 3 },
{ 9, 6, 3, 3, 3, 6, 3, 3 },
};
static u8 act_time_value[][8] = {
{ 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 0, 0, 0, 0, 0, 0, 0 },
{ 9, 9, 9, 2, 2, 7, 2, 2 },
{ 19, 19, 19, 5, 4, 14, 5, 4 },
{ 19, 19, 19, 5, 4, 14, 5, 4 },
{ 28, 28, 28, 7, 6, 21, 7, 6 },
{ 38, 38, 38, 10, 9, 28, 10, 9 },
{ 38, 38, 38, 10, 9, 28, 10, 9 },
};
static u8 rco_time_value[][8] = {
{ 0, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 0, 0, 0, 0, 0, 0, 0 },
{ 9, 2, 0, 2, 0, 7, 1, 1 },
{ 19, 5, 1, 5, 2, 16, 3, 2 },
{ 19, 5, 1, 5, 2, 16, 3, 2 },
{ 30, 9, 3, 9, 4, 25, 6, 4 },
{ 40, 12, 4, 12, 5, 34, 12, 5 },
{ 40, 12, 4, 12, 5, 34, 12, 5 },
};
/*
* Printing configuration
*/
/* Used for chipset type printing at boot time */
static char *chipset_capability[] = {
"ATA", "ATA 16",
"ATA 33", "ATA 66",
"ATA 100 (1st gen)", "ATA 100 (2nd gen)",
"ATA 133 (1st gen)", "ATA 133 (2nd gen)"
};
/*
* Configuration functions
*/
static u8 sis_ata133_get_base(ide_drive_t *drive)
{
struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
u32 reg54 = 0;
pci_read_config_dword(dev, 0x54, ®54);
return ((reg54 & 0x40000000) ? 0x70 : 0x40) + drive->dn * 4;
}
static void sis_ata16_program_timings(ide_drive_t *drive, const u8 mode)
{
struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
u16 t1 = 0;
u8 drive_pci = 0x40 + drive->dn * 2;
const u16 pio_timings[] = { 0x000, 0x607, 0x404, 0x303, 0x301 };
const u16 mwdma_timings[] = { 0x008, 0x302, 0x301 };
pci_read_config_word(dev, drive_pci, &t1);
/* clear active/recovery timings */
t1 &= ~0x070f;
if (mode >= XFER_MW_DMA_0) {
if (chipset_family > ATA_16)
t1 &= ~0x8000; /* disable UDMA */
t1 |= mwdma_timings[mode - XFER_MW_DMA_0];
} else
t1 |= pio_timings[mode - XFER_PIO_0];
pci_write_config_word(dev, drive_pci, t1);
}
static void sis_ata100_program_timings(ide_drive_t *drive, const u8 mode)
{
struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
u8 t1, drive_pci = 0x40 + drive->dn * 2;
/* timing bits: 7:4 active 3:0 recovery */
const u8 pio_timings[] = { 0x00, 0x67, 0x44, 0x33, 0x31 };
const u8 mwdma_timings[] = { 0x08, 0x32, 0x31 };
if (mode >= XFER_MW_DMA_0) {
u8 t2 = 0;
pci_read_config_byte(dev, drive_pci, &t2);
t2 &= ~0x80; /* disable UDMA */
pci_write_config_byte(dev, drive_pci, t2);
t1 = mwdma_timings[mode - XFER_MW_DMA_0];
} else
t1 = pio_timings[mode - XFER_PIO_0];
pci_write_config_byte(dev, drive_pci + 1, t1);
}
static void sis_ata133_program_timings(ide_drive_t *drive, const u8 mode)
{
struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
u32 t1 = 0;
u8 drive_pci = sis_ata133_get_base(drive), clk, idx;
pci_read_config_dword(dev, drive_pci, &t1);
t1 &= 0xc0c00fff;
clk = (t1 & 0x08) ? ATA_133 : ATA_100;
if (mode >= XFER_MW_DMA_0) {
t1 &= ~0x04; /* disable UDMA */
idx = mode - XFER_MW_DMA_0 + 5;
} else
idx = mode - XFER_PIO_0;
t1 |= ini_time_value[clk][idx] << 12;
t1 |= act_time_value[clk][idx] << 16;
t1 |= rco_time_value[clk][idx] << 24;
pci_write_config_dword(dev, drive_pci, t1);
}
static void sis_program_timings(ide_drive_t *drive, const u8 mode)
{
if (chipset_family < ATA_100) /* ATA_16/33/66/100a */
sis_ata16_program_timings(drive, mode);
else if (chipset_family < ATA_133) /* ATA_100/133a */
sis_ata100_program_timings(drive, mode);
else /* ATA_133 */
sis_ata133_program_timings(drive, mode);
}
static void config_drive_art_rwp(ide_drive_t *drive)
{
ide_hwif_t *hwif = HWIF(drive);
struct pci_dev *dev = to_pci_dev(hwif->dev);
u8 reg4bh = 0;
u8 rw_prefetch = 0;
pci_read_config_byte(dev, 0x4b, ®4bh);
if (drive->media == ide_disk)
rw_prefetch = 0x11 << drive->dn;
if ((reg4bh & (0x11 << drive->dn)) != rw_prefetch)
pci_write_config_byte(dev, 0x4b, reg4bh|rw_prefetch);
}
static void sis_set_pio_mode(ide_drive_t *drive, const u8 pio)
{
config_drive_art_rwp(drive);
sis_program_timings(drive, XFER_PIO_0 + pio);
}
static void sis_ata133_program_udma_timings(ide_drive_t *drive, const u8 mode)
{
struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
u32 regdw = 0;
u8 drive_pci = sis_ata133_get_base(drive), clk, idx;
pci_read_config_dword(dev, drive_pci, ®dw);
regdw |= 0x04;
regdw &= 0xfffff00f;
/* check if ATA133 enable */
clk = (regdw & 0x08) ? ATA_133 : ATA_100;
idx = mode - XFER_UDMA_0;
regdw |= cycle_time_value[clk][idx] << 4;
regdw |= cvs_time_value[clk][idx] << 8;
pci_write_config_dword(dev, drive_pci, regdw);
}
static void sis_ata33_program_udma_timings(ide_drive_t *drive, const u8 mode)
{
struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
u8 drive_pci = 0x40 + drive->dn * 2, reg = 0, i = chipset_family;
pci_read_config_byte(dev, drive_pci + 1, ®);
/* force the UDMA bit on if we want to use UDMA */
reg |= 0x80;
/* clean reg cycle time bits */
reg &= ~((0xff >> (8 - cycle_time_range[i])) << cycle_time_offset[i]);
/* set reg cycle time bits */
reg |= cycle_time_value[i][mode - XFER_UDMA_0] << cycle_time_offset[i];
pci_write_config_byte(dev, drive_pci + 1, reg);
}
static void sis_program_udma_timings(ide_drive_t *drive, const u8 mode)
{
if (chipset_family >= ATA_133) /* ATA_133 */
sis_ata133_program_udma_timings(drive, mode);
else /* ATA_33/66/100a/100/133a */
sis_ata33_program_udma_timings(drive, mode);
}
static void sis_set_dma_mode(ide_drive_t *drive, const u8 speed)
{
if (speed >= XFER_UDMA_0)
sis_program_udma_timings(drive, speed);
else
sis_program_timings(drive, speed);
}
static u8 sis_ata133_udma_filter(ide_drive_t *drive)
{
struct pci_dev *dev = to_pci_dev(drive->hwif->dev);
u32 regdw = 0;
u8 drive_pci = sis_ata133_get_base(drive);
pci_read_config_dword(dev, drive_pci, ®dw);
/* if ATA133 disable, we should not set speed above UDMA5 */
return (regdw & 0x08) ? ATA_UDMA6 : ATA_UDMA5;
}
static int __devinit sis_find_family(struct pci_dev *dev)
{
struct pci_dev *host;
int i = 0;
chipset_family = 0;
for (i = 0; i < ARRAY_SIZE(SiSHostChipInfo) && !chipset_family; i++) {
host = pci_get_device(PCI_VENDOR_ID_SI, SiSHostChipInfo[i].host_id, NULL);
if (!host)
continue;
chipset_family = SiSHostChipInfo[i].chipset_family;
/* Special case for SiS630 : 630S/ET is ATA_100a */
if (SiSHostChipInfo[i].host_id == PCI_DEVICE_ID_SI_630) {
if (host->revision >= 0x30)
chipset_family = ATA_100a;
}
pci_dev_put(host);
printk(KERN_INFO "SIS5513: %s %s controller\n",
SiSHostChipInfo[i].name, chipset_capability[chipset_family]);
}
if (!chipset_family) { /* Belongs to pci-quirks */
u32 idemisc;
u16 trueid;
/* Disable ID masking and register remapping */
pci_read_config_dword(dev, 0x54, &idemisc);
pci_write_config_dword(dev, 0x54, (idemisc & 0x7fffffff));
pci_read_config_word(dev, PCI_DEVICE_ID, &trueid);
pci_write_config_dword(dev, 0x54, idemisc);
if (trueid == 0x5518) {
printk(KERN_INFO "SIS5513: SiS 962/963 MuTIOL IDE UDMA133 controller\n");
chipset_family = ATA_133;
/* Check for 5513 compability mapping
* We must use this, else the port enabled code will fail,
* as it expects the enablebits at 0x4a.
*/
if ((idemisc & 0x40000000) == 0) {
pci_write_config_dword(dev, 0x54, idemisc | 0x40000000);
printk(KERN_INFO "SIS5513: Switching to 5513 register mapping\n");
}
}
}
if (!chipset_family) { /* Belongs to pci-quirks */
struct pci_dev *lpc_bridge;
u16 trueid;
u8 prefctl;
u8 idecfg;
pci_read_config_byte(dev, 0x4a, &idecfg);
pci_write_config_byte(dev, 0x4a, idecfg | 0x10);
pci_read_config_word(dev, PCI_DEVICE_ID, &trueid);
pci_write_config_byte(dev, 0x4a, idecfg);
if (trueid == 0x5517) { /* SiS 961/961B */
lpc_bridge = pci_get_slot(dev->bus, 0x10); /* Bus 0, Dev 2, Fn 0 */
pci_read_config_byte(dev, 0x49, &prefctl);
pci_dev_put(lpc_bridge);
if (lpc_bridge->revision == 0x10 && (prefctl & 0x80)) {
printk(KERN_INFO "SIS5513: SiS 961B MuTIOL IDE UDMA133 controller\n");
chipset_family = ATA_133a;
} else {
printk(KERN_INFO "SIS5513: SiS 961 MuTIOL IDE UDMA100 controller\n");
chipset_family = ATA_100;
}
}
}
return chipset_family;
}
static unsigned int __devinit init_chipset_sis5513(struct pci_dev *dev,
const char *name)
{
/* Make general config ops here
1/ tell IDE channels to operate in Compatibility mode only
2/ tell old chips to allow per drive IDE timings */
u8 reg;
u16 regw;
switch (chipset_family) {
case ATA_133:
/* SiS962 operation mode */
pci_read_config_word(dev, 0x50, ®w);
if (regw & 0x08)
pci_write_config_word(dev, 0x50, regw&0xfff7);
pci_read_config_word(dev, 0x52, ®w);
if (regw & 0x08)
pci_write_config_word(dev, 0x52, regw&0xfff7);
break;
case ATA_133a:
case ATA_100:
/* Fixup latency */
pci_write_config_byte(dev, PCI_LATENCY_TIMER, 0x80);
/* Set compatibility bit */
pci_read_config_byte(dev, 0x49, ®);
if (!(reg & 0x01))
pci_write_config_byte(dev, 0x49, reg|0x01);
break;
case ATA_100a:
case ATA_66:
/* Fixup latency */
pci_write_config_byte(dev, PCI_LATENCY_TIMER, 0x10);
/* On ATA_66 chips the bit was elsewhere */
pci_read_config_byte(dev, 0x52, ®);
if (!(reg & 0x04))
pci_write_config_byte(dev, 0x52, reg|0x04);
break;
case ATA_33:
/* On ATA_33 we didn't have a single bit to set */
pci_read_config_byte(dev, 0x09, ®);
if ((reg & 0x0f) != 0x00)
pci_write_config_byte(dev, 0x09, reg&0xf0);
case ATA_16:
/* force per drive recovery and active timings
needed on ATA_33 and below chips */
pci_read_config_byte(dev, 0x52, ®);
if (!(reg & 0x08))
pci_write_config_byte(dev, 0x52, reg|0x08);
break;
}
return 0;
}
struct sis_laptop {
u16 device;
u16 subvendor;
u16 subdevice;
};
static const struct sis_laptop sis_laptop[] = {
/* devid, subvendor, subdev */
{ 0x5513, 0x1043, 0x1107 }, /* ASUS A6K */
{ 0x5513, 0x1734, 0x105f }, /* FSC Amilo A1630 */
{ 0x5513, 0x1071, 0x8640 }, /* EasyNote K5305 */
/* end marker */
{ 0, }
};
static u8 __devinit sis_cable_detect(ide_hwif_t *hwif)
{
struct pci_dev *pdev = to_pci_dev(hwif->dev);
const struct sis_laptop *lap = &sis_laptop[0];
u8 ata66 = 0;
while (lap->device) {
if (lap->device == pdev->device &&
lap->subvendor == pdev->subsystem_vendor &&
lap->subdevice == pdev->subsystem_device)
return ATA_CBL_PATA40_SHORT;
lap++;
}
if (chipset_family >= ATA_133) {
u16 regw = 0;
u16 reg_addr = hwif->channel ? 0x52: 0x50;
pci_read_config_word(pdev, reg_addr, ®w);
ata66 = (regw & 0x8000) ? 0 : 1;
} else if (chipset_family >= ATA_66) {
u8 reg48h = 0;
u8 mask = hwif->channel ? 0x20 : 0x10;
pci_read_config_byte(pdev, 0x48, ®48h);
ata66 = (reg48h & mask) ? 0 : 1;
}
return ata66 ? ATA_CBL_PATA80 : ATA_CBL_PATA40;
}
static const struct ide_port_ops sis_port_ops = {
.set_pio_mode = sis_set_pio_mode,
.set_dma_mode = sis_set_dma_mode,
.cable_detect = sis_cable_detect,
};
static const struct ide_port_ops sis_ata133_port_ops = {
.set_pio_mode = sis_set_pio_mode,
.set_dma_mode = sis_set_dma_mode,
.udma_filter = sis_ata133_udma_filter,
.cable_detect = sis_cable_detect,
};
static const struct ide_port_info sis5513_chipset __devinitdata = {
.name = "SIS5513",
.init_chipset = init_chipset_sis5513,
.enablebits = { {0x4a, 0x02, 0x02}, {0x4a, 0x04, 0x04} },
.host_flags = IDE_HFLAG_LEGACY_IRQS | IDE_HFLAG_NO_AUTODMA,
.pio_mask = ATA_PIO4,
.mwdma_mask = ATA_MWDMA2,
};
static int __devinit sis5513_init_one(struct pci_dev *dev, const struct pci_device_id *id)
{
struct ide_port_info d = sis5513_chipset;
u8 udma_rates[] = { 0x00, 0x00, 0x07, 0x1f, 0x3f, 0x3f, 0x7f, 0x7f };
int rc;
rc = pci_enable_device(dev);
if (rc)
return rc;
if (sis_find_family(dev) == 0)
return -ENOTSUPP;
if (chipset_family >= ATA_133)
d.port_ops = &sis_ata133_port_ops;
else
d.port_ops = &sis_port_ops;
d.udma_mask = udma_rates[chipset_family];
return ide_setup_pci_device(dev, &d);
}
static const struct pci_device_id sis5513_pci_tbl[] = {
{ PCI_VDEVICE(SI, PCI_DEVICE_ID_SI_5513), 0 },
{ PCI_VDEVICE(SI, PCI_DEVICE_ID_SI_5518), 0 },
{ PCI_VDEVICE(SI, PCI_DEVICE_ID_SI_1180), 0 },
{ 0, },
};
MODULE_DEVICE_TABLE(pci, sis5513_pci_tbl);
static struct pci_driver driver = {
.name = "SIS_IDE",
.id_table = sis5513_pci_tbl,
.probe = sis5513_init_one,
};
static int __init sis5513_ide_init(void)
{
return ide_pci_register_driver(&driver);
}
module_init(sis5513_ide_init);
MODULE_AUTHOR("Lionel Bouton, L C Chang, Andre Hedrick, Vojtech Pavlik");
MODULE_DESCRIPTION("PCI driver module for SIS IDE");
MODULE_LICENSE("GPL");
/*
* TODO:
* - CLEANUP
* - Use drivers/ide/ide-timing.h !
* - More checks in the config registers (force values instead of
* relying on the BIOS setting them correctly).
* - Further optimisations ?
* . for example ATA66+ regs 0x48 & 0x4A
*/
