Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/Documentation/mca.txt
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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File size: 11795 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | i386 Micro Channel Architecture Support |
2 | ======================================= |
3 | |
4 | MCA support is enabled using the CONFIG_MCA define. A machine with a MCA |
5 | bus will have the kernel variable MCA_bus set, assuming the BIOS feature |
6 | bits are set properly (see arch/i386/boot/setup.S for information on |
7 | how this detection is done). |
8 | |
9 | Adapter Detection |
10 | ================= |
11 | |
12 | The ideal MCA adapter detection is done through the use of the |
13 | Programmable Option Select registers. Generic functions for doing |
14 | this have been added in include/linux/mca.h and arch/i386/kernel/mca.c. |
15 | Everything needed to detect adapters and read (and write) configuration |
16 | information is there. A number of MCA-specific drivers already use |
17 | this. 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 | |
45 | Loadable modules should modify this to test that the specified IRQ and |
46 | IO ports (plus whatever other stuff) match. See 3c523.c for example |
47 | code (actually, smc-mca.c has a slightly more complex example that can |
48 | handle a list of adapter ids). |
49 | |
50 | Keep 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 |
52 | potential for blowing up hardware when it's done at the wrong time. |
53 | Furthermore, accessing a POS register disables a device temporarily. |
54 | This is usually okay during startup, but do _you_ want to rely on it? |
55 | During initial configuration, mca_init() reads all the POS registers |
56 | into memory. mca_read_stored_pos() accesses that data. mca_read_pos() |
57 | and mca_write_pos() are also available for (safer) direct POS access, |
58 | but their use is _highly_ discouraged. mca_write_pos() is particularly |
59 | dangerous, as it is possible for adapters to be put in inconsistent |
60 | states (i.e. sharing IO address, etc) and may result in crashes, toasted |
61 | hardware, and blindness. |
62 | |
63 | User level drivers (such as the AGX X server) can use /proc/mca/pos to |
64 | find adapters (see below). |
65 | |
66 | Some MCA adapters can also be detected via the usual ISA-style device |
67 | probing (many SCSI adapters, for example). This sort of thing is highly |
68 | discouraged. Perfectly good information is available telling you what's |
69 | there, so there's no excuse for messing with random IO ports. However, |
70 | we MCA people still appreciate any ISA-style driver that will work with |
71 | our hardware. You take what you can get... |
72 | |
73 | Level-Triggered Interrupts |
74 | ========================== |
75 | |
76 | Because MCA uses level-triggered interrupts, a few problems arise with |
77 | what might best be described as the ISA mindset and its effects on |
78 | drivers. These sorts of problems are expected to become less common as |
79 | more people use shared IRQs on PCI machines. |
80 | |
81 | In general, an interrupt must be acknowledged not only at the ICU (which |
82 | is done automagically by the kernel), but at the device level. In |
83 | particular, IRQ 0 must be reset after a timer interrupt (now done in |
84 | arch/i386/kernel/time.c) or the first timer interrupt hangs the system. |
85 | There were also problems with the 1.3.x floppy drivers, but that seems |
86 | to have been fixed. |
87 | |
88 | IRQs are also shareable, and most MCA-specific devices should be coded |
89 | with shared IRQs in mind. |
90 | |
91 | /proc/mca |
92 | ========= |
93 | |
94 | /proc/mca is a directory containing various files for adapters and |
95 | other 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 | |
103 | See Appendix A for a sample. |
104 | |
105 | Device drivers can easily add their own information function for |
106 | specific slots (including integrated ones) via the |
107 | mca_set_adapter_procfn() call. Drivers that support this are ESDI, IBM |
108 | SCSI, and 3c523. If a device is also a module, make sure that the proc |
109 | function is removed in the module cleanup. This will require storing |
110 | the slot information in a private structure somewhere. See the 3c523 |
111 | driver for details. |
112 | |
113 | Your 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 | |
128 | Some of the standard MCA information will already be printed, so don't |
129 | bother repeating it. Don't try putting in more than 3K of information. |
130 | |
131 | Enable this function with: |
132 | mca_set_adapter_procfn( slot, dev_getinfo, dev ); |
133 | |
134 | Disable it with: |
135 | mca_set_adapter_procfn( slot, NULL, NULL ); |
136 | |
137 | It is also recommended that, even if you don't write a proc function, to |
138 | set the name of the adapter (i.e. "PS/2 ESDI Controller") via |
139 | mca_set_adapter_name( int slot, char* name ). |
140 | |
141 | MCA Device Drivers |
142 | ================== |
143 | |
144 | Currently, there are a number of MCA-specific device drivers. |
145 | |
146 | 1) 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 | |
153 | 2) 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 | |
162 | 3) 3c523 |
163 | drivers/net/3c523.c |
164 | drivers/net/3c523.h |
165 | 3Com 3c523 Etherlink/MC ethernet driver. |
166 | |
167 | 4) 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 | |
173 | 5) 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 | |
180 | 6) 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 | |
185 | Also added boot time option of scsi-probe, which can do reordering of |
186 | SCSI host adapters. This will direct the kernel on the order which |
187 | SCSI adapter should be detected. Example: |
188 | scsi-probe=ibmmca,fd_mcs,adaptec1542,buslogic |
189 | |
190 | The serial drivers were modified to support the extended IO port range |
191 | of the typical MCA system (also #ifdef CONFIG_MCA). |
192 | |
193 | The following devices work with existing drivers: |
194 | 1) Token-ring |
195 | 2) Future Domain SCSI (MCS-600, MCS-700, not MCS-350, OEM'ed IBM SCSI) |
196 | 3) Adaptec 1640 SCSI (using the aha1542 driver) |
197 | 4) Bustek/Buslogic SCSI (various) |
198 | 5) Probably all Arcnet cards. |
199 | 6) Some, possibly all, MCA IDE controllers. |
200 | 7) 3Com 3c529 (MCA version of 3c509) (patched) |
201 | |
202 | 8) Intel EtherExpressMC (patched version) |
203 | You need to have CONFIG_MCA defined to have EtherExpressMC support. |
204 | 9) Reply Sound Blaster/SCSI (SB part) (patched version) |
205 | |
206 | Bugs & Other Weirdness |
207 | ====================== |
208 | |
209 | NMIs tend to occur with MCA machines because of various hardware |
210 | weirdness, bus timeouts, and many other non-critical things. Some basic |
211 | code to handle them (inspired by the NetBSD MCA code) has been added to |
212 | detect the guilty device, but it's pretty incomplete. If NMIs are a |
213 | persistent problem (on some model 70 or 80s, they occur every couple |
214 | shell commands), the CONFIG_IGNORE_NMI flag will take care of that. |
215 | |
216 | Various Pentium machines have had serious problems with the FPU test in |
217 | bugs.h. Basically, the machine hangs after the HLT test. This occurs, |
218 | as far as we know, on the Pentium-equipped 85s, 95s, and some PC Servers. |
219 | The PCI/MCA PC 750s are fine as far as I can tell. The ``mca-pentium'' |
220 | boot-prompt flag will disable the FPU bug check if this is a problem |
221 | with your machine. |
222 | |
223 | The model 80 has a raft of problems that are just too weird and unique |
224 | to get into here. Some people have no trouble while others have nothing |
225 | but problems. I'd suspect some problems are related to the age of the |
226 | average 80 and accompanying hardware deterioration, although others |
227 | are definitely design problems with the hardware. Among the problems |
228 | include SCSI controller problems, ESDI controller problems, and serious |
229 | screw-ups in the floppy controller. Oh, and the parallel port is also |
230 | pretty flaky. There were about 5 or 6 different model 80 motherboards |
231 | produced to fix various obscure problems. As far as I know, it's pretty |
232 | much impossible to tell which bugs a particular model 80 has (other than |
233 | triggering them, that is). |
234 | |
235 | Drivers are required for some MCA memory adapters. If you're suddenly |
236 | short a few megs of RAM, this might be the reason. The (I think) Enhanced |
237 | Memory Adapter commonly found on the model 70 is one. There's a very |
238 | alpha driver floating around, but it's pretty ugly (disassembled from |
239 | the DOS driver, actually). See the MCA Linux web page (URL below) |
240 | for more current memory info. |
241 | |
242 | The Thinkpad 700 and 720 will work, but various components are either |
243 | non-functional, flaky, or we don't know anything about them. The |
244 | graphics controller is supposed to be some WD, but we can't get things |
245 | working properly. The PCMCIA slots don't seem to work. Ditto for APM. |
246 | The serial ports work, but detection seems to be flaky. |
247 | |
248 | Credits |
249 | ======= |
250 | A whole pile of people have contributed to the MCA code. I'd include |
251 | their names here, but I don't have a list handy. Check the MCA Linux |
252 | home page (URL below) for a perpetually out-of-date list. |
253 | |
254 | ===================================================================== |
255 | MCA Linux Home Page: http://glycerine.itsmm.uni.edu/mca/ |
256 | |
257 | Christophe Beauregard |
258 | chrisb@truespectra.com |
259 | cpbeaure@calum.csclub.uwaterloo.ca |
260 | |
261 | ===================================================================== |
262 | Appendix A: Sample /proc/mca |
263 | |
264 | This is from my model 8595. Slot 1 contains the standard IBM SCSI |
265 | adapter, slot 3 is an Adaptec AHA-1640, slot 5 is a XGA-1 video adapter, |
266 | and slot 7 is the 3c523 Etherlink/MC. |
267 | |
268 | /proc/mca/machine: |
269 | Model Id: 0xf8 |
270 | Submodel Id: 0x14 |
271 | BIOS Revision: 0x5 |
272 | |
273 | /proc/mca/pos: |
274 | Slot 1: ff 8e f1 fc a0 ff ff ff IBM SCSI Adapter w/Cache |
275 | Slot 2: ff ff ff ff ff ff ff ff |
276 | Slot 3: 1f 0f 81 3b bf b6 ff ff |
277 | Slot 4: ff ff ff ff ff ff ff ff |
278 | Slot 5: db 8f 1d 5e fd c0 00 00 |
279 | Slot 6: ff ff ff ff ff ff ff ff |
280 | Slot 7: 42 60 ff 08 ff ff ff ff 3Com 3c523 Etherlink/MC |
281 | Slot 8: ff ff ff ff ff ff ff ff |
282 | Video : ff ff ff ff ff ff ff ff |
283 | SCSI : ff ff ff ff ff ff ff ff |
284 | |
285 | /proc/mca/slot1: |
286 | Slot: 1 |
287 | Adapter Name: IBM SCSI Adapter w/Cache |
288 | Id: 8eff |
289 | Enabled: Yes |
290 | POS: ff 8e f1 fc a0 ff ff ff |
291 | Subsystem PUN: 7 |
292 | Detected at boot: Yes |
293 | |
294 | /proc/mca/slot3: |
295 | Slot: 3 |
296 | Adapter Name: Unknown |
297 | Id: 0f1f |
298 | Enabled: Yes |
299 | POS: 1f 0f 81 3b bf b6 ff ff |
300 | |
301 | /proc/mca/slot5: |
302 | Slot: 5 |
303 | Adapter Name: Unknown |
304 | Id: 8fdb |
305 | Enabled: Yes |
306 | POS: db 8f 1d 5e fd c0 00 00 |
307 | |
308 | /proc/mca/slot7: |
309 | Slot: 7 |
310 | Adapter Name: 3Com 3c523 Etherlink/MC |
311 | Id: 6042 |
312 | Enabled: Yes |
313 | POS: 42 60 ff 08 ff ff ff ff |
314 | Revision: 0xe |
315 | IRQ: 9 |
316 | IO Address: 0x3300-0x3308 |
317 | Memory: 0xd8000-0xdbfff |
318 | Transceiver: External |
319 | Device: eth0 |
320 | Hardware Address: 02 60 8c 45 c4 2a |