Based on kernel version 3.4. Page generated on 2012-05-21 22:07 EST.
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/x86/kernel/mca_32.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/x86/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 SCSI 147 drivers/scsi/ibmmca.c 148 drivers/scsi/ibmmca.h 149 The driver for the IBM SCSI subsystem. Includes both integrated 150 controllers and adapter cards. May require command-line arg 151 "ibmmcascsi=io_port" to force detection of an adapter. If you have a 152 machine with a front-panel display (i.e. model 95), you can use 153 "ibmmcascsi=display" to enable a drive activity indicator. 154 155 2) 3c523 156 drivers/net/3c523.c 157 drivers/net/3c523.h 158 3Com 3c523 Etherlink/MC ethernet driver. 159 160 3) SMC Ultra/MCA and IBM Adapter/A 161 drivers/net/smc-mca.c 162 drivers/net/smc-mca.h 163 Driver for the MCA version of the SMC Ultra and various other 164 OEM'ed and work-alike cards (Elite, Adapter/A, etc). 165 166 4) NE/2 167 driver/net/ne2.c 168 driver/net/ne2.h 169 The NE/2 is the MCA version of the NE2000. This may not work 170 with clones that have a different adapter id than the original 171 NE/2. 172 173 5) Future Domain MCS-600/700, OEM'd IBM Fast SCSI Adapter/A and 174 Reply Sound Blaster/SCSI (SCSI part) 175 Better support for these cards than the driver for ISA. 176 Supports multiple cards with IRQ sharing. 177 178 Also added boot time option of scsi-probe, which can do reordering of 179 SCSI host adapters. This will direct the kernel on the order which 180 SCSI adapter should be detected. Example: 181 scsi-probe=ibmmca,fd_mcs,adaptec1542,buslogic 182 183 The serial drivers were modified to support the extended IO port range 184 of the typical MCA system (also #ifdef CONFIG_MCA). 185 186 The following devices work with existing drivers: 187 1) Token-ring 188 2) Future Domain SCSI (MCS-600, MCS-700, not MCS-350, OEM'ed IBM SCSI) 189 3) Adaptec 1640 SCSI (using the aha1542 driver) 190 4) Bustek/Buslogic SCSI (various) 191 5) Probably all Arcnet cards. 192 6) Some, possibly all, MCA IDE controllers. 193 7) 3Com 3c529 (MCA version of 3c509) (patched) 194 195 8) Intel EtherExpressMC (patched version) 196 You need to have CONFIG_MCA defined to have EtherExpressMC support. 197 9) Reply Sound Blaster/SCSI (SB part) (patched version) 198 199 Bugs & Other Weirdness 200 ====================== 201 202 NMIs tend to occur with MCA machines because of various hardware 203 weirdness, bus timeouts, and many other non-critical things. Some basic 204 code to handle them (inspired by the NetBSD MCA code) has been added to 205 detect the guilty device, but it's pretty incomplete. If NMIs are a 206 persistent problem (on some model 70 or 80s, they occur every couple 207 shell commands), the CONFIG_IGNORE_NMI flag will take care of that. 208 209 Various Pentium machines have had serious problems with the FPU test in 210 bugs.h. Basically, the machine hangs after the HLT test. This occurs, 211 as far as we know, on the Pentium-equipped 85s, 95s, and some PC Servers. 212 The PCI/MCA PC 750s are fine as far as I can tell. The ``mca-pentium'' 213 boot-prompt flag will disable the FPU bug check if this is a problem 214 with your machine. 215 216 The model 80 has a raft of problems that are just too weird and unique 217 to get into here. Some people have no trouble while others have nothing 218 but problems. I'd suspect some problems are related to the age of the 219 average 80 and accompanying hardware deterioration, although others 220 are definitely design problems with the hardware. Among the problems 221 include SCSI controller problems, ESDI controller problems, and serious 222 screw-ups in the floppy controller. Oh, and the parallel port is also 223 pretty flaky. There were about 5 or 6 different model 80 motherboards 224 produced to fix various obscure problems. As far as I know, it's pretty 225 much impossible to tell which bugs a particular model 80 has (other than 226 triggering them, that is). 227 228 Drivers are required for some MCA memory adapters. If you're suddenly 229 short a few megs of RAM, this might be the reason. The (I think) Enhanced 230 Memory Adapter commonly found on the model 70 is one. There's a very 231 alpha driver floating around, but it's pretty ugly (disassembled from 232 the DOS driver, actually). See the MCA Linux web page (URL below) 233 for more current memory info. 234 235 The Thinkpad 700 and 720 will work, but various components are either 236 non-functional, flaky, or we don't know anything about them. The 237 graphics controller is supposed to be some WD, but we can't get things 238 working properly. The PCMCIA slots don't seem to work. Ditto for APM. 239 The serial ports work, but detection seems to be flaky. 240 241 Credits 242 ======= 243 A whole pile of people have contributed to the MCA code. I'd include 244 their names here, but I don't have a list handy. Check the MCA Linux 245 home page (URL below) for a perpetually out-of-date list. 246 247 ===================================================================== 248 MCA Linux Home Page: http://www.dgmicro.com/mca/ 249 250 Christophe Beauregard 251 chrisb@truespectra.com 252 cpbeaure@calum.csclub.uwaterloo.ca 253 254 ===================================================================== 255 Appendix A: Sample /proc/mca 256 257 This is from my model 8595. Slot 1 contains the standard IBM SCSI 258 adapter, slot 3 is an Adaptec AHA-1640, slot 5 is a XGA-1 video adapter, 259 and slot 7 is the 3c523 Etherlink/MC. 260 261 /proc/mca/machine: 262 Model Id: 0xf8 263 Submodel Id: 0x14 264 BIOS Revision: 0x5 265 266 /proc/mca/pos: 267 Slot 1: ff 8e f1 fc a0 ff ff ff IBM SCSI Adapter w/Cache 268 Slot 2: ff ff ff ff ff ff ff ff 269 Slot 3: 1f 0f 81 3b bf b6 ff ff 270 Slot 4: ff ff ff ff ff ff ff ff 271 Slot 5: db 8f 1d 5e fd c0 00 00 272 Slot 6: ff ff ff ff ff ff ff ff 273 Slot 7: 42 60 ff 08 ff ff ff ff 3Com 3c523 Etherlink/MC 274 Slot 8: ff ff ff ff ff ff ff ff 275 Video : ff ff ff ff ff ff ff ff 276 SCSI : ff ff ff ff ff ff ff ff 277 278 /proc/mca/slot1: 279 Slot: 1 280 Adapter Name: IBM SCSI Adapter w/Cache 281 Id: 8eff 282 Enabled: Yes 283 POS: ff 8e f1 fc a0 ff ff ff 284 Subsystem PUN: 7 285 Detected at boot: Yes 286 287 /proc/mca/slot3: 288 Slot: 3 289 Adapter Name: Unknown 290 Id: 0f1f 291 Enabled: Yes 292 POS: 1f 0f 81 3b bf b6 ff ff 293 294 /proc/mca/slot5: 295 Slot: 5 296 Adapter Name: Unknown 297 Id: 8fdb 298 Enabled: Yes 299 POS: db 8f 1d 5e fd c0 00 00 300 301 /proc/mca/slot7: 302 Slot: 7 303 Adapter Name: 3Com 3c523 Etherlink/MC 304 Id: 6042 305 Enabled: Yes 306 POS: 42 60 ff 08 ff ff ff ff 307 Revision: 0xe 308 IRQ: 9 309 IO Address: 0x3300-0x3308 310 Memory: 0xd8000-0xdbfff 311 Transceiver: External 312 Device: eth0 313 Hardware Address: 02 60 8c 45 c4 2a