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 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===================================================================== 255MCA Linux Home Page: http://glycerine.itsmm.uni.edu/mca/ 256 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 321