README.ide -- Information regarding ide.c and ide-cd.c (IDE driver in 1.3.x)
================================================================================
Supported by:  mlord@bnr.ca           -- disks, interfaces, probing
               snyder@fnald0.fnal.gov -- cdroms, ATAPI, audio

   +-----------------------------------------------------------------+
   |  The hdparm utility for controlling various IDE features is     |
   |  packaged separately.  Look for it on popular linux FTP sites.  |
   +-----------------------------------------------------------------+

See description later on below for handling BIG IDE drives with >1024 cyls.

Major features of ide.c & ide-cd.c:

NEW!	- support for up to *four* IDE interfaces on one or more IRQs
NEW!	- support for any mix of up to *eight* disk and/or cdrom drives
	- support for reading IDE ATAPI cdrom drives (NEC,MITSUMI,VERTOS,SONY)
	- support for audio functions
	- auto-detection of interfaces, drives, IRQs, and disk geometries
		- "single" drives should be jumpered as "master", not "slave"
NEW!		  (both are now probed for)
	- support for BIOSs which report "more than 16 heads" on disk drives
	- uses LBA (slightly faster) on disk drives which support it
	- support for lots of fancy (E)IDE drive functions with hdparm utility
	- optional (compile time) support for 32-bit VLB data transfers
	- support for IDE multiple (block) mode (same as hd.c)
	- support for interrupt unmasking during I/O (better than hd.c)
	- improved handshaking and error detection/recovery
	- can co-exist with hd.c controlling the first interface
	- run-time selectable 32bit interface support (using hdparm-2.3)
NEW!	- support for reliable operation of buggy RZ1000 interfaces
		- PCI support is automatic
NEW!	- support for reliable operation of buggy CMD-640 interfaces
		- PCI support is automatic
		- for VLB, use kernel command line option:   ide0=cmd640_vlb
		- this support also enables the secondary i/f on most cards
		- experimental interface timing parameter support
NEW!	- experimental support for UMC 8672 interfaces
NEW!	- support for secondary interface on the FGI/Holtek HT-6560B VLB i/f
		- use kernel command line option:   ide1=ht6560
NEW!	- experimental "fast" speed support for QD6580 interfaces
		- use kernel command line option:   ide0=qd6580
NEW!	- experimental support for DTC-2278D interfaces
		- use kernel command line option:   ide1=dtc2278
NEW!	- support for drives with a stuck WRERR_STAT bit
NEW!	- support for removeable devices, including door lock/unlock
NEW!	- transparent support for DiskManager 6.0x and "Dynamic Disk Overlay"
	- works with Linux fdisk, LILO, loadlin, bootln, etc..
NEW!	- mostly transparent support for EZ-Drive
NEW!		- to use LILO with EZ, install LILO on the linux partition
		  rather than on the master boot record, and then mark the
		  linux partition as "bootable" or "active" using fdisk.
		  (courtesy of Juha Laiho <jlaiho@ichaos.nullnet.fi>).
NEW!	- ide-cd.c now compiles separate from ide.c
NEW!	- Bus-Master DMA support for Intel PCI Triton chipset IDE interfaces
		- for details, see comments at top of triton.c
NEW!    - ide-cd.c now supports door locking and auto-loading.
		- Also preliminary support for multisession
		  and direct reads of audio data.

For work in progress, see the comments in ide.c, ide-cd.c, and triton.c.

Note that there is now a group actively working on support for the Promise
caching IDE cards, such as the DC4030VL, and early results are encouraging.
Look for this support to be added to the kernel soon.


***  IMPORTANT NOTICES (for kernel versions prior to 1.3.22)
***  =================
***  "CMD" EIDE Interfaces will not (by default) work *reliably* when drives
***  are attached to the second interface.  This is due to a flaw in the
***  hardware.  To "fix" this, supply the special kernel "command line"
***  parameter to LILO or LOADLIN:    ide1=serialize
***
***  "CMD 640B" EIDE Interfaces will not work *reliably* when "hdparm -u1"
***  (interrupt unmasking) is used.  This is due to a flaw in the hardware,
***  and is only a problem when "hdparm -u1" is used after booting.
***
***  "RZ1000" EIDE Interfaces will also not work *reliably* when "hdparm -u1"
***  (interrupt unmasking) is used.  This is due to a flaw in the hardware,
***  and is only a problem when "hdparm -u1" is used after booting.
***
***  Failure to abide by these restrictions can cause severe data corruption!


***  IMPORTANT NOTICES (for kernel versions after 1.3.21)
***  =================
***  PCI versions of the CMD640 and RZ1000 interfaces are now detected
***  automatically at startup when PCI BIOS support is configured.
***  Linux disables the "pre-fetch" or "read-ahead" modes of these interfaces
***  to prevent data corruption possible due to hardware design flaws.
***  Use of the "serialize" option is no longer necessary.
***
***  The CMD640 is also used on some Vesa Local Bus (VLB) cards, and is *NOT*
***  automatically detected by Linux.  For safe, reliable operation with such
***  interfaces, one *MUST* use the "ide0=cmd640_vlb" kernel option.
***  Use of the "serialize" option is no longer necessary.


To access devices on the 2nd/3rd/4th interfaces, device entries must first be
created in /dev for them.  To create such entries, simply run the included
shell script:   MAKEDEV.ide

Apparently many releases of Slackware 2.2/2.3 have incorrect entries
in /dev for hdc* and hdd* -- this can also be corrected by running MAKEDEV.ide

ide.c automatically probes for the primary and secondary interfaces,
for the drives/geometries attached to those interfaces, and for the
IRQ numbers being used by the interfaces (normally IRQ14 & IRQ15).

Interfaces beyond the first two are not normally probed for, but may be
specified using kernel "command line" options.  For example,

	ide3=0x1e8,0x3f0,11	/* ioports 0x1e8-0x1ef,0x3f0, irq 11 */

Normally the irq number need not be specified, as ide.c will probe for it:

	ide3=0x1e8,0x3f0	/* ioports 0x1e8-0x1ef,0x3f0 */

Any number of interfaces may share a single IRQ if necessary, at a slight
performance penalty, whether on separate cards or a single VLB card.
The IDE driver automatically detects and handles this.  However, this may
or may not be harmful to your hardware.. two or more cards driving the same IRQ
can potentially burn each other's bus driver, though in practice this
seldom occurs.  Be careful, and if in doubt, don't do it!

Drives are normally found by auto-probing and/or examining the CMOS/BIOS data.
For really weird situations, the apparent (fdisk) geometry can also be specified
on the kernel "command line" using LILO.  The format of such lines is:

	hdx=cyls,heads,sects,wpcom,irq
or	hdx=cdrom

where hdx can be any of hda through hdh, Three values are required
(cyls,heads,sects).  For example:

	hdc=1050,32,64  hdd=cdrom

either {hda,hdb} or {hdc,hdd}.  The results of successful auto-probing may
override the physical geometry/irq specified, though the "original" geometry
may be retained as the "logical" geometry for partitioning purposes (fdisk).

If the auto-probing during boot time confuses a drive (ie. the drive works
with hd.c but not with ide.c), then an command line option may be specified
for each drive for which you'd like the drive to skip the hardware
probe/identification sequence.  For example:

	hdb=noprobe
or
	hdc=768,16,32
	hdc=noprobe

Note that when only one IDE device is attached to an interface,
it should be jumpered as "single" or "master", *not* "slave".
Many folks have had "trouble" with cdroms because of this requirement,
so ide.c now probes for both units, though success is more likely
when the drive is jumpered correctly.

Courtesy of Scott Snyder, the driver supports ATAPI cdrom drives
such as the NEC-260 and the new MITSUMI triple/quad speed drives.
Such drives will be identified at boot time, just like a harddisk.

If for some reason your cdrom drive is *not* found at boot time, you can force
the probe to look harder by supplying a kernel command line parameter
via LILO, such as:

	hdc=cdrom	/* hdc = "master" on second interface */
or
	hdd=cdrom	/* hdd = "slave" on second interface */

For example, a GW2000 system might have a harddrive on the primary
interface (/dev/hda) and an IDE cdrom drive on the secondary interface
(/dev/hdc).  To mount a CD in the cdrom drive, one would use something like:

	ln -sf /dev/hdc /dev/cdrom
	mkdir /cd
	mount /dev/cdrom /cd -t iso9660 -o ro

If, after doing all of the above, mount doesn't work and you see
errors from the driver (with dmesg) complaining about `status=0xff',
this means that the hardware is not responding to the driver's attempts
to read it.  One of the following is probably the problem:

  - Your hardware is broken.

  - You are using the wrong address for the device, or you have the
    drive jumpered wrong.  Review the configuration instructions above.

  - Your IDE controller requires some nonstandard initialization sequence
    before it will work properly.  If this is the case, there will often
    be a separate MS-DOS driver just for the controller.  IDE interfaces
    on sound cards usually fall into this category.  Such configurations
    can often be made to work by first booting MS-DOS, loading the
    appropriate drivers, and then warm-booting linux (without powering
    off).  This can be automated using loadlin in the MS-DOS autoexec.

If you always get timeout errors, interrupts from the drive are probably
not making it to the host.  Check how you have the hardware jumpered
and make sure it matches what the driver expects (see the configuration
instructions above).  If you have a PCI system, also check the BIOS
setup; i've had one report of a system which was shipped with IRQ 15
disabled by the BIOS.

The kernel is able to execute binaries directly off of the cdrom,
provided it is mounted with the default block size of 1024 (as above).

Please pass on any feedback on the cdrom stuff to the author & maintainer,
Scott Snyder (snyder@fnald0.fnal.gov).

Note that if BOTH hd.c and ide.c are configured into the kernel,
hd.c will normally be allowed to control the primary IDE interface.
This is useful for older hardware that may be incompatible with ide.c,
and still allows newer hardware to run on the 2nd/3rd/4th IDE ports
under control of ide.c.   To have ide.c also "take over" the primary
IDE port in this situation, use the "command line" parameter:  ide0=0x1f0

mlord@bnr.ca
snyder@fnald0.fnal.gov
================================================================================

Summary of ide driver parameters for kernel "command line":
----------------------------------------------------------

  "hdx="  is recognized for all "x" from "a" to "h", such as "hdc".
  "idex=" is recognized for all "x" from "0" to "3", such as "ide1".
 
  "hdx=noprobe"        : drive may be present, but do not probe for it
  "hdx=nowerr"         : ignore the WRERR_STAT bit on this drive
  "hdx=cdrom"          : drive is present, and is a cdrom drive
  "hdx=cyl,head,sect"  : disk drive is present, with specified geometry
 
  "idex=noprobe"       : do not attempt to access/use this interface
  "idex=base"          : probe for an interface at the addr specified,
                               where "base" is usually 0x1f0 or 0x170
                               and "ctl" is assumed to be "base"+0x206
  "idex=base,ctl"      : specify both base and ctl
  "idex=base,ctl,irq"  : specify base, ctl, and irq number
 
  The following two are valid ONLY on ide0 or ide1,
  and the defaults for the base,ctl ports must not be altered.
 
  "idex=serialize"     : do not overlap operations on ide0 and ide1.
  "idex=dtc2278"       : enables use of DTC2278 secondary i/f
  "idex=ht6560b"       : enables use of HT6560B secondary i/f
  "idex=cmd640_vlb"    : required for VLB cards with the CMD640 chip
                         (not for PCI -- automatically detected)
 
  This option is valid ONLY on ide0, and the defaults for the base,ctl ports 
  must not be altered.
  
  "ide0=qd6580"        : select "fast" interface speed on a qd6580 interface
 
Everything else is rejected with a "BAD OPTION" message.

================================================================================

Some Terminology
----------------
IDE = Integrated Drive Electronics, meaning that each drive has a built-in
controller, which is why an "IDE interface card" is not a "controller card".

IDE drives are designed to attach almost directly to the ISA bus of an AT-style
computer.  The typical IDE interface card merely provides I/O port address
decoding and tri-state buffers, although several newer localbus cards go much
beyond the basics.  When purchasing a localbus IDE interface, avoid cards with
an onboard BIOS and those which require special drivers.  Instead, look for a
card which uses hardware switches/jumpers to select the interface timing speed,
to allow much faster data transfers than the original 8Mhz ISA bus allows.

ATA = AT (the old IBM 286 computer) Attachment Interface, a draft American
National Standard for connecting hard drives to PCs.  This is the official
name for "IDE".

The latest standards define some enhancements, known as the ATA-2 spec,
which grew out of vendor-specific "Enhanced IDE" (EIDE) implementations.

ATAPI = ATA Packet Interface, a new protocol for controlling the drives,
similar to SCSI protocols, created at the same time as the ATA2 standard.
ATAPI is currently used for controlling CDROM and TAPE devices, and will
likely also soon be used for Floppy drives, removable R/W cartridges,
and for high capacity hard disk drives.

How To Use *Big* ATA/IDE drives with Linux
------------------------------------------
The ATA Interface spec for IDE disk drives allows a total of 28 bits
(8 bits for sector, 16 bits for cylinder, and 4 bits for head) for addressing
individual disk sectors of 512 bytes each (in "Linear Block Address" (LBA)
mode, there is still only a total of 28 bits available in the hardware).
This "limits" the capacity of an IDE drive to no more than 128GB (Giga-bytes).
All current day IDE drives are somewhat smaller than this upper limit, and
within a few years, ATAPI disk drives will raise the limit considerably.

All IDE disk drives "suffer" from a "16-heads" limitation:  the hardware has
only a four bit field for head selection, restricting the number of "physical"
heads to 16 or less.  Since the BIOS usually has a 63 sectors/track limit,
this means that all IDE drivers larger than 504MB (528Meg) must use a "physical"
geometry with more than 1024 cylinders.

   (1024cyls * 16heads * 63sects * 512bytes/sector) / (1024 * 1024) == 504MB

(Some BIOSs (and controllers with onboard BIOS) pretend to allow "32" or "64"
 heads per drive (discussed below), but can only do so by playing games with
 the real (hidden) geometry, which is always limited to 16 or fewer heads).

This presents two problems to most systems:

	1. The INT13 interface to the BIOS only allows 10-bits for cylinder
	addresses, giving a limit of 1024cyls for programs which use it.

	2. The physical geometry fields of the disk partition table only
	allow 10-bits for cylinder addresses, giving a similar limit of 1024
	cyls for operating systems that do not use the "sector count" fields
	instead of the physical Cyl/Head/Sect (CHS) geometry fields.

Neither of these limitations affects Linux itself, as it (1) does not use the
BIOS for disk access, and it (2) is clever enough to use the "sector count"
fields of the partition table instead of the physical CHS geometry fields.

	a) Most folks use LILO to load linux.  LILO uses the INT13 interface
	to the BIOS to load the kernel at boot time.  Therefore, LILO can only
	load linux if the files it needs (usually just the kernel images) are
	located below the magic 1024 cylinder "boundary" (more on this later).

	b) Many folks also like to have bootable DOS partitions on their
	drive(s).  DOS also uses the INT13 interface to the BIOS, not only
	for booting, but also for operation after booting.  Therefore, DOS
	can normally only access partitions which are contained entirely below
	the magic 1024 cylinder "boundary".

There are at least seven commonly used schemes for kludging DOS to work
around this "limitation".  In the long term, the problem is being solved
by introduction of an alternative BIOS interface that does not have the
same limitations as the INT13 interface.  New versions of DOS are expected
to detect and use this interface in systems whose BIOS provides it.

But in the present day, alternative solutions are necessary.

The most popular solution in newer systems is to have the BIOS shift bits
between the cylinder and head number fields.  This is activated by entering
a translated logical geometry into the BIOS/CMOS setup for the drive.
Thus, if the drive has a geometry of 2100/16/63 (CHS), then the BIOS could
present a "logical" geometry of 525/64/63 by "shifting" two bits from the
cylinder number into the head number field for purposes of the partition table,
CMOS setup, and INT13 interfaces.  Linux kernels 1.1.39 and higher detect and
"handle" this translation automatically, making this a rather painless solution
for the 1024 cyls problem.  If for some reason Linux gets confused (unlikely),
then use the kernel command line parameters to pass the *logical* geometry,
as in:  hda=525,64,63

If the BIOS does not support this form of drive translation, then several
options remain, listed below in inverse order of popularity:

	- boot from a floppy disk instead of the hard drive (takes 10 seconds).
	- use a partition below the 1024 cyl boundary to hold the linux
	boot files (kernel images and /boot directory), and place the rest
	of linux anywhere else on the drive.  These files can reside in a DOS
	partition, or in a tailor-made linux boot partition.

If you cannot use drive translation, *and* your BIOS also restricts you to
entering no more than 1024 cylinders in the geometry field in the CMOS setup,
then just set it to 1024.  As of v3.5 of this driver, Linux automatically
determines the *real* number of cylinders for fdisk to use, allowing easy
access to the full disk capacity without having to fiddle around.

Regardless of what you do, all DOS partitions *must* be contained entirely
within the first 1024 logical cylinders.  For a 1Gig WD disk drive, here's
a good "half and half" partitioning scheme to start with:

	geometry = 2100/16/63
	/dev/hda1 from cyl    1 to  992		dos
	/dev/hda2 from cyl  993 to 1023		swap
	/dev/hda3 from cyl 1024 to 2100		linux

To ensure that LILO can boot linux, the boot files (kernel and /boot/*)
must reside within the first 1024 cylinders of the drive.  If your linux
root partition is *not* completely within the first 1024 cyls (quite common),
then you can use LILO to boot linux from files on your DOS partition
by doing the following after installing slackware (or whatever):

	0. Boot from the "boot floppy" created during the installation
        1. Mount your DOS partition as /dos (and stick it in /etc/fstab)
        2. Move your kernel (/vmlinuz) to /dos/vmlinuz with:  mv /vmlinuz /dos
        3. Edit /etc/lilo.conf to change /vmlinuz to /dos/vmlinuz
        4. Move /boot to /dos/boot with:  cp -a /boot /dos ; rm -r /boot
        5. Create a symlink for LILO to use with:  ln -s /dos/boot /boot
        6. Re-run LILO with:  lilo

	A danger with this approach is that whenever an MS-DOS "defragmentation"
	program is run (like Norton "speeddisk"), it may move the Linux boot
	files around, confusing LILO and making the (Linux) system unbootable.
	Be sure to keep a kernel "boot floppy" at hand for such circumstances.

If you "don't do DOS", then partition as you please, but remember to create
a small partition to hold the /boot directory (and vmlinuz) as described above
such that they stay within the first 1024 cylinders.

Note that when creating partitions that span beyond cylinder 1024,
Linux fdisk will complain about "Partition X has different physical/logical
endings" and emit messages such as "This is larger than 1024, and may cause
problems with some software".   Ignore this for linux partitions.  The "some
software" refers to DOS, the BIOS, and LILO, as described previously.

Western Digital ships a "DiskManager 6.03" diskette with all of their big
hard drives.  Use BIOS translation instead of this if possible, as it is a
more generally compatible method of achieving the same results (DOS access
to the entire disk).  However, if you must use DiskManager, it now works
with Linux 1.3.x in most cases.  Let me know if you still have trouble.

mlord@bnr.ca

================================================================================
EIDE card compatibility reports:
================================================================================

comp.os.linux.hardware #18483 (7 + 0 more)                            (1)--[1]
From: test <a>
[1] Re: Promise EIDEMAX
Date: Fri Aug 11 23:17:39 EDT 1995
Organization: Technical University of Brno, Czech Republic
Lines: 14
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Mailer: Mozilla 1.1N (X11; I; Linux 1.2.11 i486)
To: rmorton@VNET.IBM.COM
X-URL: news:19950806.154256.872@almaden.ibm.com

I have a Promise <sth>2300 board with DX2/80 w/ 32Mb ram.

This one is a bit schizophrenic - half (2 drives) at VLBUS and
the rest 2 on ISA.

Works quite well, Linux works with it (4 HDDs), it
also supports its dual irq mechanism (14 & 15).
In the documentation I've found that there are certain things made about this
controller(in kernel).
My current kernel is 1.2.11 and Promise should be supported in all 1.2.xx
kernels I think.

   Vladimir Myslik

comp.sys.intel #41571 (1 + 2 more)              --(1)--(1)+-(1)--(1)
From: triblet@almaden.ibm.com (Chuck Tribolet)            \-(1)--(1)--(1)--(1)
Newsgroups: comp.sys.intel,comp.os.os2.bugs
[1] Re: RZ1000 errorIntel motherboards and RZ1000
Date: Tue Aug 29 11:00:12 EDT 1995
Organization: IBM Almaden Research Center
Lines: 20
X-Newsreader: IBM NewsReader/2 v1.02

In <41ip85$gf9@park.uvsc.edu>, Terry Lambert <terry@cs.weber.edu> writes:
>Try running a real OS.  BIOS drivers so not initiate bus mastering
>DMA, and DOS does not interleave I/O.

1: The RZ1000 can't do DMA.
2: I was running OS/2 (2.11 back then).

I agreed that you might be able to concoct a benchmark that was affected,
but it has had no real world effect for me or a lot of other people.  Disabling
IDE prefetch has the effect of a small increase in PCI bus busy at a time
when the CPU is giving all it's CPU cycles to the IDE driver (because the
RZ1000 can't run DMA and the driver has to be in a PIO loop) and therefore
the CPU can't do much of anything else anyway.


Chuck Tribolet
Triblet@Almaden.IBM.Com
San Jose, CA
 
Silicon Valley - best day job in the world

================================================================================

 1995 Nov 16 at 08:25  EST
 from:       'dwhysong@dolphin.physics.ucsb.edu' (BNR400)

[I'm cc'ing this to Mark Lord: FYI, I've got at DTC2278S VLB EIDE
controller with a Connor CFA850A as /dev/hda and a Maxtor 7213A as
/dev/hdb using Linux 1.2.13 w/patches for assembly strcpy and the kswap
patches. I'm getting strange behavior and an unstable system when I try to
use 32 bit VLB data transfer to the interface card. However, hdparm
reports that the Connor is extremely fast when I can get the 32 bit mode
enabled using hdparm -c1 /dev/hd(a|b). However, if I don't do hdparm -c1
on both /dev/hda and /dev/hdb, then when I run "hdparm -t /dev/hda" the
disk subsystem locks up... the disk LED comes on and stays on, and no
other programs are able to get disk access (I can switch VC's, but I can't
get past the username prompt). I thought you should know about this. I'm
not sure if it's a problem with the support for the DTC cards, or a
peculiarity with my hardware configuration. I doubt that my hardware
itself is flaky, though that's always a possibility.]

On Wed, 15 Nov 1995, Michael Faurot wrote:

> > The trick is setting BOTH drives to use the 32 bit interface.
>
> Congrats on getting it going.  Those are some great transfer
> rates.  I noticed you did switch on the unmasking.  Noticed any
> problems with things under extreme load or with serial transfers?

I've never had any problems which I could trace to interrupt unmasking.
Of course, my system usually doesn't have a really heavy load, either.
These numbers seem way too high for a disk with something like 3500 (?)
RPM.

Sleepy# hdparm -t /dev/hda

/dev/hda:
 Timing buffer-cache reads:   32 MB in  2.24 seconds =14.29 MB/sec
 Timing buffered disk reads:  16 MB in  3.63 seconds = 4.41 MB/sec
 Estimating raw driver speed: 16 MB in  2.51 seconds = 6.37 MB/sec

> Not sure I was much help to you, but I'm glad to hear you got it
> working--and pretty impressivly at that. :-)

Mmm, well, about that... I've found that my Connor drive (/dev/hda) is
pretty fast when I have my system configured like this. I'm still not
sure I trust the "hdparm -t"  results, though. However, when I try
"hdparm -t /dev/hdb" (/dev/hdb is an older Maxtor 7213A) I have the same
problem I had before with my disk subsystem locking up.

I've tried just about every possible combination of flags in ide.c and
hdparm, and I can't get decent performance out of this drive/controller
combination without some kind of instability creeping in. I'm living with
the situation now only because /dev/hdb is a DOS-only drive, and I don't
need it under Linux. However, I don't really like the situation.

-Dave
dwhysong@physics.ucsb.edu

(Why can't this stuff be simple? Plug the card in, and it works? Every
hardware manufacturer has to have their own way of doing things...)

