1i386 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 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 1552) 3c523 156 drivers/net/3c523.c 157 drivers/net/3c523.h 158 3Com 3c523 Etherlink/MC ethernet driver. 159 1603) 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 1664) 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 1735) 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 178Also added boot time option of scsi-probe, which can do reordering of 179SCSI host adapters. This will direct the kernel on the order which 180SCSI adapter should be detected. Example: 181 scsi-probe=ibmmca,fd_mcs,adaptec1542,buslogic 182 183The serial drivers were modified to support the extended IO port range 184of the typical MCA system (also #ifdef CONFIG_MCA). 185 186The following devices work with existing drivers: 1871) Token-ring 1882) Future Domain SCSI (MCS-600, MCS-700, not MCS-350, OEM'ed IBM SCSI) 1893) Adaptec 1640 SCSI (using the aha1542 driver) 1904) Bustek/Buslogic SCSI (various) 1915) Probably all Arcnet cards. 1926) Some, possibly all, MCA IDE controllers. 1937) 3Com 3c529 (MCA version of 3c509) (patched) 194 1958) Intel EtherExpressMC (patched version) 196 You need to have CONFIG_MCA defined to have EtherExpressMC support. 1979) Reply Sound Blaster/SCSI (SB part) (patched version) 198 199Bugs & Other Weirdness 200====================== 201 202NMIs tend to occur with MCA machines because of various hardware 203weirdness, bus timeouts, and many other non-critical things. Some basic 204code to handle them (inspired by the NetBSD MCA code) has been added to 205detect the guilty device, but it's pretty incomplete. If NMIs are a 206persistent problem (on some model 70 or 80s, they occur every couple 207shell commands), the CONFIG_IGNORE_NMI flag will take care of that. 208 209Various Pentium machines have had serious problems with the FPU test in 210bugs.h. Basically, the machine hangs after the HLT test. This occurs, 211as far as we know, on the Pentium-equipped 85s, 95s, and some PC Servers. 212The PCI/MCA PC 750s are fine as far as I can tell. The ``mca-pentium'' 213boot-prompt flag will disable the FPU bug check if this is a problem 214with your machine. 215 216The model 80 has a raft of problems that are just too weird and unique 217to get into here. Some people have no trouble while others have nothing 218but problems. I'd suspect some problems are related to the age of the 219average 80 and accompanying hardware deterioration, although others 220are definitely design problems with the hardware. Among the problems 221include SCSI controller problems, ESDI controller problems, and serious 222screw-ups in the floppy controller. Oh, and the parallel port is also 223pretty flaky. There were about 5 or 6 different model 80 motherboards 224produced to fix various obscure problems. As far as I know, it's pretty 225much impossible to tell which bugs a particular model 80 has (other than 226triggering them, that is). 227 228Drivers are required for some MCA memory adapters. If you're suddenly 229short a few megs of RAM, this might be the reason. The (I think) Enhanced 230Memory Adapter commonly found on the model 70 is one. There's a very 231alpha driver floating around, but it's pretty ugly (disassembled from 232the DOS driver, actually). See the MCA Linux web page (URL below) 233for more current memory info. 234 235The Thinkpad 700 and 720 will work, but various components are either 236non-functional, flaky, or we don't know anything about them. The 237graphics controller is supposed to be some WD, but we can't get things 238working properly. The PCMCIA slots don't seem to work. Ditto for APM. 239The serial ports work, but detection seems to be flaky. 240 241Credits 242======= 243A whole pile of people have contributed to the MCA code. I'd include 244their names here, but I don't have a list handy. Check the MCA Linux 245home page (URL below) for a perpetually out-of-date list. 246 247===================================================================== 248MCA Linux Home Page: http://www.dgmicro.com/mca/ 249 250Christophe Beauregard 251chrisb@truespectra.com 252cpbeaure@calum.csclub.uwaterloo.ca 253 254===================================================================== 255Appendix A: Sample /proc/mca 256 257This is from my model 8595. Slot 1 contains the standard IBM SCSI 258adapter, slot 3 is an Adaptec AHA-1640, slot 5 is a XGA-1 video adapter, 259and slot 7 is the 3c523 Etherlink/MC. 260 261/proc/mca/machine: 262Model Id: 0xf8 263Submodel Id: 0x14 264BIOS Revision: 0x5 265 266/proc/mca/pos: 267Slot 1: ff 8e f1 fc a0 ff ff ff IBM SCSI Adapter w/Cache 268Slot 2: ff ff ff ff ff ff ff ff 269Slot 3: 1f 0f 81 3b bf b6 ff ff 270Slot 4: ff ff ff ff ff ff ff ff 271Slot 5: db 8f 1d 5e fd c0 00 00 272Slot 6: ff ff ff ff ff ff ff ff 273Slot 7: 42 60 ff 08 ff ff ff ff 3Com 3c523 Etherlink/MC 274Slot 8: ff ff ff ff ff ff ff ff 275Video : ff ff ff ff ff ff ff ff 276SCSI : ff ff ff ff ff ff ff ff 277 278/proc/mca/slot1: 279Slot: 1 280Adapter Name: IBM SCSI Adapter w/Cache 281Id: 8eff 282Enabled: Yes 283POS: ff 8e f1 fc a0 ff ff ff 284Subsystem PUN: 7 285Detected at boot: Yes 286 287/proc/mca/slot3: 288Slot: 3 289Adapter Name: Unknown 290Id: 0f1f 291Enabled: Yes 292POS: 1f 0f 81 3b bf b6 ff ff 293 294/proc/mca/slot5: 295Slot: 5 296Adapter Name: Unknown 297Id: 8fdb 298Enabled: Yes 299POS: db 8f 1d 5e fd c0 00 00 300 301/proc/mca/slot7: 302Slot: 7 303Adapter Name: 3Com 3c523 Etherlink/MC 304Id: 6042 305Enabled: Yes 306POS: 42 60 ff 08 ff ff ff ff 307Revision: 0xe 308IRQ: 9 309IO Address: 0x3300-0x3308 310Memory: 0xd8000-0xdbfff 311Transceiver: External 312Device: eth0 313Hardware Address: 02 60 8c 45 c4 2a 314