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Linus Torvalds1da177e2005-04-16 15:20:36 -07001i386 Micro Channel Architecture Support
2=======================================
3
4MCA support is enabled using the CONFIG_MCA define. A machine with a MCA
5bus will have the kernel variable MCA_bus set, assuming the BIOS feature
6bits are set properly (see arch/i386/boot/setup.S for information on
7how this detection is done).
8
9Adapter Detection
10=================
11
12The ideal MCA adapter detection is done through the use of the
13Programmable Option Select registers. Generic functions for doing
14this have been added in include/linux/mca.h and arch/i386/kernel/mca.c.
15Everything needed to detect adapters and read (and write) configuration
16information is there. A number of MCA-specific drivers already use
17this. The typical probe code looks like the following:
18
19 #include <linux/mca.h>
20
21 unsigned char pos2, pos3, pos4, pos5;
22 struct net_device* dev;
23 int slot;
24
25 if( MCA_bus ) {
26 slot = mca_find_adapter( ADAPTER_ID, 0 );
27 if( slot == MCA_NOTFOUND ) {
28 return -ENODEV;
29 }
30 /* optional - see below */
31 mca_set_adapter_name( slot, "adapter name & description" );
32 mca_set_adapter_procfn( slot, dev_getinfo, dev );
33
34 /* read the POS registers. Most devices only use 2 and 3 */
35 pos2 = mca_read_stored_pos( slot, 2 );
36 pos3 = mca_read_stored_pos( slot, 3 );
37 pos4 = mca_read_stored_pos( slot, 4 );
38 pos5 = mca_read_stored_pos( slot, 5 );
39 } else {
40 return -ENODEV;
41 }
42
43 /* extract configuration from pos[2345] and set everything up */
44
45Loadable modules should modify this to test that the specified IRQ and
46IO ports (plus whatever other stuff) match. See 3c523.c for example
47code (actually, smc-mca.c has a slightly more complex example that can
48handle a list of adapter ids).
49
50Keep in mind that devices should never directly access the POS registers
51(via inb(), outb(), etc). While it's generally safe, there is a small
52potential for blowing up hardware when it's done at the wrong time.
53Furthermore, accessing a POS register disables a device temporarily.
54This is usually okay during startup, but do _you_ want to rely on it?
55During initial configuration, mca_init() reads all the POS registers
56into memory. mca_read_stored_pos() accesses that data. mca_read_pos()
57and mca_write_pos() are also available for (safer) direct POS access,
58but their use is _highly_ discouraged. mca_write_pos() is particularly
59dangerous, as it is possible for adapters to be put in inconsistent
60states (i.e. sharing IO address, etc) and may result in crashes, toasted
61hardware, and blindness.
62
63User level drivers (such as the AGX X server) can use /proc/mca/pos to
64find adapters (see below).
65
66Some MCA adapters can also be detected via the usual ISA-style device
67probing (many SCSI adapters, for example). This sort of thing is highly
68discouraged. Perfectly good information is available telling you what's
69there, so there's no excuse for messing with random IO ports. However,
70we MCA people still appreciate any ISA-style driver that will work with
71our hardware. You take what you can get...
72
73Level-Triggered Interrupts
74==========================
75
76Because MCA uses level-triggered interrupts, a few problems arise with
77what might best be described as the ISA mindset and its effects on
78drivers. These sorts of problems are expected to become less common as
79more people use shared IRQs on PCI machines.
80
81In general, an interrupt must be acknowledged not only at the ICU (which
82is done automagically by the kernel), but at the device level. In
83particular, IRQ 0 must be reset after a timer interrupt (now done in
84arch/i386/kernel/time.c) or the first timer interrupt hangs the system.
85There were also problems with the 1.3.x floppy drivers, but that seems
86to have been fixed.
87
88IRQs are also shareable, and most MCA-specific devices should be coded
89with shared IRQs in mind.
90
91/proc/mca
92=========
93
94/proc/mca is a directory containing various files for adapters and
95other stuff.
96
97 /proc/mca/pos Straight listing of POS registers
98 /proc/mca/slot[1-8] Information on adapter in specific slot
99 /proc/mca/video Same for integrated video
100 /proc/mca/scsi Same for integrated SCSI
101 /proc/mca/machine Machine information
102
103See Appendix A for a sample.
104
105Device drivers can easily add their own information function for
106specific slots (including integrated ones) via the
107mca_set_adapter_procfn() call. Drivers that support this are ESDI, IBM
108SCSI, and 3c523. If a device is also a module, make sure that the proc
109function is removed in the module cleanup. This will require storing
110the slot information in a private structure somewhere. See the 3c523
111driver for details.
112
113Your typical proc function will look something like this:
114
115 static int
116 dev_getinfo( char* buf, int slot, void* d ) {
117 struct net_device* dev = (struct net_device*) d;
118 int len = 0;
119
120 len += sprintf( buf+len, "Device: %s\n", dev->name );
121 len += sprintf( buf+len, "IRQ: %d\n", dev->irq );
122 len += sprintf( buf+len, "IO Port: %#lx-%#lx\n", ... );
123 ...
124
125 return len;
126 }
127
128Some of the standard MCA information will already be printed, so don't
129bother repeating it. Don't try putting in more than 3K of information.
130
131Enable this function with:
132 mca_set_adapter_procfn( slot, dev_getinfo, dev );
133
134Disable it with:
135 mca_set_adapter_procfn( slot, NULL, NULL );
136
137It is also recommended that, even if you don't write a proc function, to
138set the name of the adapter (i.e. "PS/2 ESDI Controller") via
139mca_set_adapter_name( int slot, char* name ).
140
141MCA Device Drivers
142==================
143
144Currently, there are a number of MCA-specific device drivers.
145
1461) PS/2 ESDI
147 drivers/block/ps2esdi.c
148 include/linux/ps2esdi.h
149 Uses major number 36, and should use /dev files /dev/eda, /dev/edb.
150 Supports two drives, but only one controller. May use the
151 command-line args "ed=cyl,head,sec" and "tp720".
152
1532) PS/2 SCSI
154 drivers/scsi/ibmmca.c
155 drivers/scsi/ibmmca.h
156 The driver for the IBM SCSI subsystem. Includes both integrated
157 controllers and adapter cards. May require command-line arg
158 "ibmmcascsi=io_port" to force detection of an adapter. If you have a
159 machine with a front-panel display (i.e. model 95), you can use
160 "ibmmcascsi=display" to enable a drive activity indicator.
161
1623) 3c523
163 drivers/net/3c523.c
164 drivers/net/3c523.h
165 3Com 3c523 Etherlink/MC ethernet driver.
166
1674) SMC Ultra/MCA and IBM Adapter/A
168 drivers/net/smc-mca.c
169 drivers/net/smc-mca.h
170 Driver for the MCA version of the SMC Ultra and various other
171 OEM'ed and work-alike cards (Elite, Adapter/A, etc).
172
1735) NE/2
174 driver/net/ne2.c
175 driver/net/ne2.h
176 The NE/2 is the MCA version of the NE2000. This may not work
177 with clones that have a different adapter id than the original
178 NE/2.
179
1806) Future Domain MCS-600/700, OEM'd IBM Fast SCSI Aapter/A and
181 Reply Sound Blaster/SCSI (SCSI part)
182 Better support for these cards than the driver for ISA.
183 Supports multiple cards with IRQ sharing.
184
185Also added boot time option of scsi-probe, which can do reordering of
186SCSI host adapters. This will direct the kernel on the order which
187SCSI adapter should be detected. Example:
188 scsi-probe=ibmmca,fd_mcs,adaptec1542,buslogic
189
190The serial drivers were modified to support the extended IO port range
191of the typical MCA system (also #ifdef CONFIG_MCA).
192
193The following devices work with existing drivers:
1941) Token-ring
1952) Future Domain SCSI (MCS-600, MCS-700, not MCS-350, OEM'ed IBM SCSI)
1963) Adaptec 1640 SCSI (using the aha1542 driver)
1974) Bustek/Buslogic SCSI (various)
1985) Probably all Arcnet cards.
1996) Some, possibly all, MCA IDE controllers.
2007) 3Com 3c529 (MCA version of 3c509) (patched)
201
2028) Intel EtherExpressMC (patched version)
203 You need to have CONFIG_MCA defined to have EtherExpressMC support.
2049) Reply Sound Blaster/SCSI (SB part) (patched version)
205
206Bugs & Other Weirdness
207======================
208
209NMIs tend to occur with MCA machines because of various hardware
210weirdness, bus timeouts, and many other non-critical things. Some basic
211code to handle them (inspired by the NetBSD MCA code) has been added to
212detect the guilty device, but it's pretty incomplete. If NMIs are a
213persistent problem (on some model 70 or 80s, they occur every couple
214shell commands), the CONFIG_IGNORE_NMI flag will take care of that.
215
216Various Pentium machines have had serious problems with the FPU test in
217bugs.h. Basically, the machine hangs after the HLT test. This occurs,
218as far as we know, on the Pentium-equipped 85s, 95s, and some PC Servers.
219The PCI/MCA PC 750s are fine as far as I can tell. The ``mca-pentium''
220boot-prompt flag will disable the FPU bug check if this is a problem
221with your machine.
222
223The model 80 has a raft of problems that are just too weird and unique
224to get into here. Some people have no trouble while others have nothing
225but problems. I'd suspect some problems are related to the age of the
226average 80 and accompanying hardware deterioration, although others
227are definitely design problems with the hardware. Among the problems
228include SCSI controller problems, ESDI controller problems, and serious
229screw-ups in the floppy controller. Oh, and the parallel port is also
230pretty flaky. There were about 5 or 6 different model 80 motherboards
231produced to fix various obscure problems. As far as I know, it's pretty
232much impossible to tell which bugs a particular model 80 has (other than
233triggering them, that is).
234
235Drivers are required for some MCA memory adapters. If you're suddenly
236short a few megs of RAM, this might be the reason. The (I think) Enhanced
237Memory Adapter commonly found on the model 70 is one. There's a very
238alpha driver floating around, but it's pretty ugly (disassembled from
239the DOS driver, actually). See the MCA Linux web page (URL below)
240for more current memory info.
241
242The Thinkpad 700 and 720 will work, but various components are either
243non-functional, flaky, or we don't know anything about them. The
244graphics controller is supposed to be some WD, but we can't get things
245working properly. The PCMCIA slots don't seem to work. Ditto for APM.
246The serial ports work, but detection seems to be flaky.
247
248Credits
249=======
250A whole pile of people have contributed to the MCA code. I'd include
251their names here, but I don't have a list handy. Check the MCA Linux
252home page (URL below) for a perpetually out-of-date list.
253
254=====================================================================
Randy Dunlap98766fb2005-11-21 21:32:31 -0800255MCA Linux Home Page: http://www.dgmicro.com/mca/
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256
257Christophe Beauregard
258chrisb@truespectra.com
259cpbeaure@calum.csclub.uwaterloo.ca
260
261=====================================================================
262Appendix A: Sample /proc/mca
263
264This is from my model 8595. Slot 1 contains the standard IBM SCSI
265adapter, slot 3 is an Adaptec AHA-1640, slot 5 is a XGA-1 video adapter,
266and slot 7 is the 3c523 Etherlink/MC.
267
268/proc/mca/machine:
269Model Id: 0xf8
270Submodel Id: 0x14
271BIOS Revision: 0x5
272
273/proc/mca/pos:
274Slot 1: ff 8e f1 fc a0 ff ff ff IBM SCSI Adapter w/Cache
275Slot 2: ff ff ff ff ff ff ff ff
276Slot 3: 1f 0f 81 3b bf b6 ff ff
277Slot 4: ff ff ff ff ff ff ff ff
278Slot 5: db 8f 1d 5e fd c0 00 00
279Slot 6: ff ff ff ff ff ff ff ff
280Slot 7: 42 60 ff 08 ff ff ff ff 3Com 3c523 Etherlink/MC
281Slot 8: ff ff ff ff ff ff ff ff
282Video : ff ff ff ff ff ff ff ff
283SCSI : ff ff ff ff ff ff ff ff
284
285/proc/mca/slot1:
286Slot: 1
287Adapter Name: IBM SCSI Adapter w/Cache
288Id: 8eff
289Enabled: Yes
290POS: ff 8e f1 fc a0 ff ff ff
291Subsystem PUN: 7
292Detected at boot: Yes
293
294/proc/mca/slot3:
295Slot: 3
296Adapter Name: Unknown
297Id: 0f1f
298Enabled: Yes
299POS: 1f 0f 81 3b bf b6 ff ff
300
301/proc/mca/slot5:
302Slot: 5
303Adapter Name: Unknown
304Id: 8fdb
305Enabled: Yes
306POS: db 8f 1d 5e fd c0 00 00
307
308/proc/mca/slot7:
309Slot: 7
310Adapter Name: 3Com 3c523 Etherlink/MC
311Id: 6042
312Enabled: Yes
313POS: 42 60 ff 08 ff ff ff ff
314Revision: 0xe
315IRQ: 9
316IO Address: 0x3300-0x3308
317Memory: 0xd8000-0xdbfff
318Transceiver: External
319Device: eth0
320Hardware Address: 02 60 8c 45 c4 2a