Root/Documentation/ide/ide.txt

1
2    Information regarding the Enhanced IDE drive in Linux 2.6
3
4==============================================================================
5
6
7   The hdparm utility can be used to control various IDE features on a
8   running system. It is packaged separately. Please Look for it on popular
9   linux FTP sites.
10
11
12
13*** IMPORTANT NOTICES: BUGGY IDE CHIPSETS CAN CORRUPT DATA!!
14*** =================
15*** PCI versions of the CMD640 and RZ1000 interfaces are now detected
16*** automatically at startup when PCI BIOS support is configured.
17***
18*** Linux disables the "prefetch" ("readahead") mode of the RZ1000
19*** to prevent data corruption possible due to hardware design flaws.
20***
21*** For the CMD640, linux disables "IRQ unmasking" (hdparm -u1) on any
22*** drive for which the "prefetch" mode of the CMD640 is turned on.
23*** If "prefetch" is disabled (hdparm -p8), then "IRQ unmasking" can be
24*** used again.
25***
26*** For the CMD640, linux disables "32bit I/O" (hdparm -c1) on any drive
27*** for which the "prefetch" mode of the CMD640 is turned off.
28*** If "prefetch" is enabled (hdparm -p9), then "32bit I/O" can be
29*** used again.
30***
31*** The CMD640 is also used on some Vesa Local Bus (VLB) cards, and is *NOT*
32*** automatically detected by Linux. For safe, reliable operation with such
33*** interfaces, one *MUST* use the "cmd640.probe_vlb" kernel option.
34***
35*** Use of the "serialize" option is no longer necessary.
36
37================================================================================
38Common pitfalls:
39
40- 40-conductor IDE cables are capable of transferring data in DMA modes up to
41  udma2, but no faster.
42
43- If possible devices should be attached to separate channels if they are
44  available. Typically the disk on the first and CD-ROM on the second.
45
46- If you mix devices on the same cable, please consider using similar devices
47  in respect of the data transfer mode they support.
48
49- Even better try to stick to the same vendor and device type on the same
50  cable.
51
52================================================================================
53
54This is the multiple IDE interface driver, as evolved from hd.c.
55
56It supports up to 9 IDE interfaces per default, on one or more IRQs (usually
5714 & 15). There can be up to two drives per interface, as per the ATA-6 spec.
58
59Primary: ide0, port 0x1f0; major=3; hda is minor=0; hdb is minor=64
60Secondary: ide1, port 0x170; major=22; hdc is minor=0; hdd is minor=64
61Tertiary: ide2, port 0x1e8; major=33; hde is minor=0; hdf is minor=64
62Quaternary: ide3, port 0x168; major=34; hdg is minor=0; hdh is minor=64
63fifth.. ide4, usually PCI, probed
64sixth.. ide5, usually PCI, probed
65
66To access devices on interfaces > ide0, device entries please make sure that
67device files for them are present in /dev. If not, please create such
68entries, by using /dev/MAKEDEV.
69
70This driver automatically probes for most IDE interfaces (including all PCI
71ones), for the drives/geometries attached to those interfaces, and for the IRQ
72lines being used by the interfaces (normally 14, 15 for ide0/ide1).
73
74Any number of interfaces may share a single IRQ if necessary, at a slight
75performance penalty, whether on separate cards or a single VLB card.
76The IDE driver automatically detects and handles this. However, this may
77or may not be harmful to your hardware.. two or more cards driving the same IRQ
78can potentially burn each other's bus driver, though in practice this
79seldom occurs. Be careful, and if in doubt, don't do it!
80
81Drives are normally found by auto-probing and/or examining the CMOS/BIOS data.
82For really weird situations, the apparent (fdisk) geometry can also be specified
83on the kernel "command line" using LILO. The format of such lines is:
84
85    ide_core.chs=[interface_number.device_number]:cyls,heads,sects
86or ide_core.cdrom=[interface_number.device_number]
87
88For example:
89
90    ide_core.chs=1.0:1050,32,64 ide_core.cdrom=1.1
91
92The results of successful auto-probing may override the physical geometry/irq
93specified, though the "original" geometry may be retained as the "logical"
94geometry for partitioning purposes (fdisk).
95
96If the auto-probing during boot time confuses a drive (ie. the drive works
97with hd.c but not with ide.c), then an command line option may be specified
98for each drive for which you'd like the drive to skip the hardware
99probe/identification sequence. For example:
100
101    ide_core.noprobe=0.1
102or
103    ide_core.chs=1.0:768,16,32
104    ide_core.noprobe=1.0
105
106Note that when only one IDE device is attached to an interface, it should be
107jumpered as "single" or "master", *not* "slave". Many folks have had
108"trouble" with cdroms because of this requirement, so the driver now probes
109for both units, though success is more likely when the drive is jumpered
110correctly.
111
112Courtesy of Scott Snyder and others, the driver supports ATAPI cdrom drives
113such as the NEC-260 and the new MITSUMI triple/quad speed drives.
114Such drives will be identified at boot time, just like a hard disk.
115
116If for some reason your cdrom drive is *not* found at boot time, you can force
117the probe to look harder by supplying a kernel command line parameter
118via LILO, such as:
119
120    ide_core.cdrom=1.0 /* "master" on second interface (hdc) */
121or
122    ide_core.cdrom=1.1 /* "slave" on second interface (hdd) */
123
124For example, a GW2000 system might have a hard drive on the primary
125interface (/dev/hda) and an IDE cdrom drive on the secondary interface
126(/dev/hdc). To mount a CD in the cdrom drive, one would use something like:
127
128    ln -sf /dev/hdc /dev/cdrom
129    mkdir /mnt/cdrom
130    mount /dev/cdrom /mnt/cdrom -t iso9660 -o ro
131
132If, after doing all of the above, mount doesn't work and you see
133errors from the driver (with dmesg) complaining about `status=0xff',
134this means that the hardware is not responding to the driver's attempts
135to read it. One of the following is probably the problem:
136
137  - Your hardware is broken.
138
139  - You are using the wrong address for the device, or you have the
140    drive jumpered wrong. Review the configuration instructions above.
141
142  - Your IDE controller requires some nonstandard initialization sequence
143    before it will work properly. If this is the case, there will often
144    be a separate MS-DOS driver just for the controller. IDE interfaces
145    on sound cards usually fall into this category. Such configurations
146    can often be made to work by first booting MS-DOS, loading the
147    appropriate drivers, and then warm-booting linux (without powering
148    off). This can be automated using loadlin in the MS-DOS autoexec.
149
150If you always get timeout errors, interrupts from the drive are probably
151not making it to the host. Check how you have the hardware jumpered
152and make sure it matches what the driver expects (see the configuration
153instructions above). If you have a PCI system, also check the BIOS
154setup; I've had one report of a system which was shipped with IRQ 15
155disabled by the BIOS.
156
157The kernel is able to execute binaries directly off of the cdrom,
158provided it is mounted with the default block size of 1024 (as above).
159
160Please pass on any feedback on any of this stuff to the maintainer,
161whose address can be found in linux/MAINTAINERS.
162
163The IDE driver is modularized. The high level disk/CD-ROM/tape/floppy
164drivers can always be compiled as loadable modules, the chipset drivers
165can only be compiled into the kernel, and the core code (ide.c) can be
166compiled as a loadable module provided no chipset support is needed.
167
168When using ide.c as a module in combination with kmod, add:
169
170    alias block-major-3 ide-probe
171
172to /etc/modprobe.conf.
173
174When ide.c is used as a module, you can pass command line parameters to the
175driver using the "options=" keyword to insmod, while replacing any ',' with
176';'.
177
178
179================================================================================
180
181Summary of ide driver parameters for kernel command line
182--------------------------------------------------------
183
184For legacy IDE VLB host drivers (ali14xx/dtc2278/ht6560b/qd65xx/umc8672)
185you need to explicitly enable probing by using "probe" kernel parameter,
186i.e. to enable probing for ALI M14xx chipsets (ali14xx host driver) use:
187
188* "ali14xx.probe" boot option when ali14xx driver is built-in the kernel
189
190* "probe" module parameter when ali14xx driver is compiled as module
191  ("modprobe ali14xx probe")
192
193Also for legacy CMD640 host driver (cmd640) you need to use "probe_vlb"
194kernel paremeter to enable probing for VLB version of the chipset (PCI ones
195are detected automatically).
196
197You also need to use "probe" kernel parameter for ide-4drives driver
198(support for IDE generic chipset with four drives on one port).
199
200To enable support for IDE doublers on Amiga use "doubler" kernel parameter
201for gayle host driver (i.e. "gayle.doubler" if the driver is built-in).
202
203To force ignoring cable detection (this should be needed only if you're using
204short 40-wires cable which cannot be automatically detected - if this is not
205a case please report it as a bug instead) use "ignore_cable" kernel parameter:
206
207* "ide_core.ignore_cable=[interface_number]" boot option if IDE is built-in
208  (i.e. "ide_core.ignore_cable=1" to force ignoring cable for "ide1")
209
210* "ignore_cable=[interface_number]" module parameter (for ide_core module)
211  if IDE is compiled as module
212
213Other kernel parameters for ide_core are:
214
215* "nodma=[interface_number.device_number]" to disallow DMA for a device
216
217* "noflush=[interface_number.device_number]" to disable flush requests
218
219* "nohpa=[interface_number.device_number]" to disable Host Protected Area
220
221* "noprobe=[interface_number.device_number]" to skip probing
222
223* "nowerr=[interface_number.device_number]" to ignore the WRERR_STAT bit
224
225* "cdrom=[interface_number.device_number]" to force device as a CD-ROM
226
227* "chs=[interface_number.device_number]" to force device as a disk (using CHS)
228
229================================================================================
230
231Some Terminology
232----------------
233IDE = Integrated Drive Electronics, meaning that each drive has a built-in
234controller, which is why an "IDE interface card" is not a "controller card".
235
236ATA = AT (the old IBM 286 computer) Attachment Interface, a draft American
237National Standard for connecting hard drives to PCs. This is the official
238name for "IDE".
239
240The latest standards define some enhancements, known as the ATA-6 spec,
241which grew out of vendor-specific "Enhanced IDE" (EIDE) implementations.
242
243ATAPI = ATA Packet Interface, a new protocol for controlling the drives,
244similar to SCSI protocols, created at the same time as the ATA2 standard.
245ATAPI is currently used for controlling CDROM, TAPE and FLOPPY (ZIP or
246LS120/240) devices, removable R/W cartridges, and for high capacity hard disk
247drives.
248
249mlord@pobox.com
250--
251
252Wed Apr 17 22:52:44 CEST 2002 edited by Marcin Dalecki, the current
253maintainer.
254
255Wed Aug 20 22:31:29 CEST 2003 updated ide boot options to current ide.c
256comments at 2.6.0-test4 time. Maciej Soltysiak <solt@dns.toxicfilms.tv>
257

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