1===================== 2The Linux IPMI Driver 3===================== 4 5:Author: Corey Minyard <minyard@mvista.com> / <minyard@acm.org> 6 7The Intelligent Platform Management Interface, or IPMI, is a 8standard for controlling intelligent devices that monitor a system. 9It provides for dynamic discovery of sensors in the system and the 10ability to monitor the sensors and be informed when the sensor's 11values change or go outside certain boundaries. It also has a 12standardized database for field-replaceable units (FRUs) and a watchdog 13timer. 14 15To use this, you need an interface to an IPMI controller in your 16system (called a Baseboard Management Controller, or BMC) and 17management software that can use the IPMI system. 18 19This document describes how to use the IPMI driver for Linux. If you 20are not familiar with IPMI itself, see the web site at 21https://www.intel.com/design/servers/ipmi/index.htm. IPMI is a big 22subject and I can't cover it all here! 23 24Configuration 25------------- 26 27The Linux IPMI driver is modular, which means you have to pick several 28things to have it work right depending on your hardware. Most of 29these are available in the 'Character Devices' menu then the IPMI 30menu. 31 32No matter what, you must pick 'IPMI top-level message handler' to use 33IPMI. What you do beyond that depends on your needs and hardware. 34 35The message handler does not provide any user-level interfaces. 36Kernel code (like the watchdog) can still use it. If you need access 37from userland, you need to select 'Device interface for IPMI' if you 38want access through a device driver. 39 40The driver interface depends on your hardware. If your system 41properly provides the SMBIOS info for IPMI, the driver will detect it 42and just work. If you have a board with a standard interface (These 43will generally be either "KCS", "SMIC", or "BT", consult your hardware 44manual), choose the 'IPMI SI handler' option. A driver also exists 45for direct I2C access to the IPMI management controller. Some boards 46support this, but it is unknown if it will work on every board. For 47this, choose 'IPMI SMBus handler', but be ready to try to do some 48figuring to see if it will work on your system if the SMBIOS/APCI 49information is wrong or not present. It is fairly safe to have both 50these enabled and let the drivers auto-detect what is present. 51 52You should generally enable ACPI on your system, as systems with IPMI 53can have ACPI tables describing them. 54 55If you have a standard interface and the board manufacturer has done 56their job correctly, the IPMI controller should be automatically 57detected (via ACPI or SMBIOS tables) and should just work. Sadly, 58many boards do not have this information. The driver attempts 59standard defaults, but they may not work. If you fall into this 60situation, you need to read the section below named 'The SI Driver' or 61"The SMBus Driver" on how to hand-configure your system. 62 63IPMI defines a standard watchdog timer. You can enable this with the 64'IPMI Watchdog Timer' config option. If you compile the driver into 65the kernel, then via a kernel command-line option you can have the 66watchdog timer start as soon as it initializes. It also have a lot 67of other options, see the 'Watchdog' section below for more details. 68Note that you can also have the watchdog continue to run if it is 69closed (by default it is disabled on close). Go into the 'Watchdog 70Cards' menu, enable 'Watchdog Timer Support', and enable the option 71'Disable watchdog shutdown on close'. 72 73IPMI systems can often be powered off using IPMI commands. Select 74'IPMI Poweroff' to do this. The driver will auto-detect if the system 75can be powered off by IPMI. It is safe to enable this even if your 76system doesn't support this option. This works on ATCA systems, the 77Radisys CPI1 card, and any IPMI system that supports standard chassis 78management commands. 79 80If you want the driver to put an event into the event log on a panic, 81enable the 'Generate a panic event to all BMCs on a panic' option. If 82you want the whole panic string put into the event log using OEM 83events, enable the 'Generate OEM events containing the panic string' 84option. You can also enable these dynamically by setting the module 85parameter named "panic_op" in the ipmi_msghandler module to "event" 86or "string". Setting that parameter to "none" disables this function. 87 88Basic Design 89------------ 90 91The Linux IPMI driver is designed to be very modular and flexible, you 92only need to take the pieces you need and you can use it in many 93different ways. Because of that, it's broken into many chunks of 94code. These chunks (by module name) are: 95 96ipmi_msghandler - This is the central piece of software for the IPMI 97system. It handles all messages, message timing, and responses. The 98IPMI users tie into this, and the IPMI physical interfaces (called 99System Management Interfaces, or SMIs) also tie in here. This 100provides the kernelland interface for IPMI, but does not provide an 101interface for use by application processes. 102 103ipmi_devintf - This provides a userland IOCTL interface for the IPMI 104driver, each open file for this device ties in to the message handler 105as an IPMI user. 106 107ipmi_si - A driver for various system interfaces. This supports KCS, 108SMIC, and BT interfaces. Unless you have an SMBus interface or your 109own custom interface, you probably need to use this. 110 111ipmi_ssif - A driver for accessing BMCs on the SMBus. It uses the 112I2C kernel driver's SMBus interfaces to send and receive IPMI messages 113over the SMBus. 114 115ipmi_powernv - A driver for access BMCs on POWERNV systems. 116 117ipmi_watchdog - IPMI requires systems to have a very capable watchdog 118timer. This driver implements the standard Linux watchdog timer 119interface on top of the IPMI message handler. 120 121ipmi_poweroff - Some systems support the ability to be turned off via 122IPMI commands. 123 124bt-bmc - This is not part of the main driver, but instead a driver for 125accessing a BMC-side interface of a BT interface. It is used on BMCs 126running Linux to provide an interface to the host. 127 128These are all individually selectable via configuration options. 129 130Much documentation for the interface is in the include files. The 131IPMI include files are: 132 133linux/ipmi.h - Contains the user interface and IOCTL interface for IPMI. 134 135linux/ipmi_smi.h - Contains the interface for system management interfaces 136(things that interface to IPMI controllers) to use. 137 138linux/ipmi_msgdefs.h - General definitions for base IPMI messaging. 139 140 141Addressing 142---------- 143 144The IPMI addressing works much like IP addresses, you have an overlay 145to handle the different address types. The overlay is:: 146 147 struct ipmi_addr 148 { 149 int addr_type; 150 short channel; 151 char data[IPMI_MAX_ADDR_SIZE]; 152 }; 153 154The addr_type determines what the address really is. The driver 155currently understands two different types of addresses. 156 157"System Interface" addresses are defined as:: 158 159 struct ipmi_system_interface_addr 160 { 161 int addr_type; 162 short channel; 163 }; 164 165and the type is IPMI_SYSTEM_INTERFACE_ADDR_TYPE. This is used for talking 166straight to the BMC on the current card. The channel must be 167IPMI_BMC_CHANNEL. 168 169Messages that are destined to go out on the IPMB bus use the 170IPMI_IPMB_ADDR_TYPE address type. The format is:: 171 172 struct ipmi_ipmb_addr 173 { 174 int addr_type; 175 short channel; 176 unsigned char slave_addr; 177 unsigned char lun; 178 }; 179 180The "channel" here is generally zero, but some devices support more 181than one channel, it corresponds to the channel as defined in the IPMI 182spec. 183 184 185Messages 186-------- 187 188Messages are defined as:: 189 190 struct ipmi_msg 191 { 192 unsigned char netfn; 193 unsigned char lun; 194 unsigned char cmd; 195 unsigned char *data; 196 int data_len; 197 }; 198 199The driver takes care of adding/stripping the header information. The 200data portion is just the data to be send (do NOT put addressing info 201here) or the response. Note that the completion code of a response is 202the first item in "data", it is not stripped out because that is how 203all the messages are defined in the spec (and thus makes counting the 204offsets a little easier :-). 205 206When using the IOCTL interface from userland, you must provide a block 207of data for "data", fill it, and set data_len to the length of the 208block of data, even when receiving messages. Otherwise the driver 209will have no place to put the message. 210 211Messages coming up from the message handler in kernelland will come in 212as:: 213 214 struct ipmi_recv_msg 215 { 216 struct list_head link; 217 218 /* The type of message as defined in the "Receive Types" 219 defines above. */ 220 int recv_type; 221 222 ipmi_user_t *user; 223 struct ipmi_addr addr; 224 long msgid; 225 struct ipmi_msg msg; 226 227 /* Call this when done with the message. It will presumably free 228 the message and do any other necessary cleanup. */ 229 void (*done)(struct ipmi_recv_msg *msg); 230 231 /* Place-holder for the data, don't make any assumptions about 232 the size or existence of this, since it may change. */ 233 unsigned char msg_data[IPMI_MAX_MSG_LENGTH]; 234 }; 235 236You should look at the receive type and handle the message 237appropriately. 238 239 240The Upper Layer Interface (Message Handler) 241------------------------------------------- 242 243The upper layer of the interface provides the users with a consistent 244view of the IPMI interfaces. It allows multiple SMI interfaces to be 245addressed (because some boards actually have multiple BMCs on them) 246and the user should not have to care what type of SMI is below them. 247 248 249Watching For Interfaces 250^^^^^^^^^^^^^^^^^^^^^^^ 251 252When your code comes up, the IPMI driver may or may not have detected 253if IPMI devices exist. So you might have to defer your setup until 254the device is detected, or you might be able to do it immediately. 255To handle this, and to allow for discovery, you register an SMI 256watcher with ipmi_smi_watcher_register() to iterate over interfaces 257and tell you when they come and go. 258 259 260Creating the User 261^^^^^^^^^^^^^^^^^ 262 263To use the message handler, you must first create a user using 264ipmi_create_user. The interface number specifies which SMI you want 265to connect to, and you must supply callback functions to be called 266when data comes in. The callback function can run at interrupt level, 267so be careful using the callbacks. This also allows to you pass in a 268piece of data, the handler_data, that will be passed back to you on 269all calls. 270 271Once you are done, call ipmi_destroy_user() to get rid of the user. 272 273From userland, opening the device automatically creates a user, and 274closing the device automatically destroys the user. 275 276 277Messaging 278^^^^^^^^^ 279 280To send a message from kernel-land, the ipmi_request_settime() call does 281pretty much all message handling. Most of the parameter are 282self-explanatory. However, it takes a "msgid" parameter. This is NOT 283the sequence number of messages. It is simply a long value that is 284passed back when the response for the message is returned. You may 285use it for anything you like. 286 287Responses come back in the function pointed to by the ipmi_recv_hndl 288field of the "handler" that you passed in to ipmi_create_user(). 289Remember again, these may be running at interrupt level. Remember to 290look at the receive type, too. 291 292From userland, you fill out an ipmi_req_t structure and use the 293IPMICTL_SEND_COMMAND ioctl. For incoming stuff, you can use select() 294or poll() to wait for messages to come in. However, you cannot use 295read() to get them, you must call the IPMICTL_RECEIVE_MSG with the 296ipmi_recv_t structure to actually get the message. Remember that you 297must supply a pointer to a block of data in the msg.data field, and 298you must fill in the msg.data_len field with the size of the data. 299This gives the receiver a place to actually put the message. 300 301If the message cannot fit into the data you provide, you will get an 302EMSGSIZE error and the driver will leave the data in the receive 303queue. If you want to get it and have it truncate the message, us 304the IPMICTL_RECEIVE_MSG_TRUNC ioctl. 305 306When you send a command (which is defined by the lowest-order bit of 307the netfn per the IPMI spec) on the IPMB bus, the driver will 308automatically assign the sequence number to the command and save the 309command. If the response is not receive in the IPMI-specified 5 310seconds, it will generate a response automatically saying the command 311timed out. If an unsolicited response comes in (if it was after 5 312seconds, for instance), that response will be ignored. 313 314In kernelland, after you receive a message and are done with it, you 315MUST call ipmi_free_recv_msg() on it, or you will leak messages. Note 316that you should NEVER mess with the "done" field of a message, that is 317required to properly clean up the message. 318 319Note that when sending, there is an ipmi_request_supply_msgs() call 320that lets you supply the smi and receive message. This is useful for 321pieces of code that need to work even if the system is out of buffers 322(the watchdog timer uses this, for instance). You supply your own 323buffer and own free routines. This is not recommended for normal use, 324though, since it is tricky to manage your own buffers. 325 326 327Events and Incoming Commands 328^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 329 330The driver takes care of polling for IPMI events and receiving 331commands (commands are messages that are not responses, they are 332commands that other things on the IPMB bus have sent you). To receive 333these, you must register for them, they will not automatically be sent 334to you. 335 336To receive events, you must call ipmi_set_gets_events() and set the 337"val" to non-zero. Any events that have been received by the driver 338since startup will immediately be delivered to the first user that 339registers for events. After that, if multiple users are registered 340for events, they will all receive all events that come in. 341 342For receiving commands, you have to individually register commands you 343want to receive. Call ipmi_register_for_cmd() and supply the netfn 344and command name for each command you want to receive. You also 345specify a bitmask of the channels you want to receive the command from 346(or use IPMI_CHAN_ALL for all channels if you don't care). Only one 347user may be registered for each netfn/cmd/channel, but different users 348may register for different commands, or the same command if the 349channel bitmasks do not overlap. 350 351From userland, equivalent IOCTLs are provided to do these functions. 352 353 354The Lower Layer (SMI) Interface 355------------------------------- 356 357As mentioned before, multiple SMI interfaces may be registered to the 358message handler, each of these is assigned an interface number when 359they register with the message handler. They are generally assigned 360in the order they register, although if an SMI unregisters and then 361another one registers, all bets are off. 362 363The ipmi_smi.h defines the interface for management interfaces, see 364that for more details. 365 366 367The SI Driver 368------------- 369 370The SI driver allows KCS, BT, and SMIC interfaces to be configured 371in the system. It discovers interfaces through a host of different 372methods, depending on the system. 373 374You can specify up to four interfaces on the module load line and 375control some module parameters:: 376 377 modprobe ipmi_si.o type=<type1>,<type2>.... 378 ports=<port1>,<port2>... addrs=<addr1>,<addr2>... 379 irqs=<irq1>,<irq2>... 380 regspacings=<sp1>,<sp2>,... regsizes=<size1>,<size2>,... 381 regshifts=<shift1>,<shift2>,... 382 slave_addrs=<addr1>,<addr2>,... 383 force_kipmid=<enable1>,<enable2>,... 384 kipmid_max_busy_us=<ustime1>,<ustime2>,... 385 unload_when_empty=[0|1] 386 trydmi=[0|1] tryacpi=[0|1] 387 tryplatform=[0|1] trypci=[0|1] 388 389Each of these except try... items is a list, the first item for the 390first interface, second item for the second interface, etc. 391 392The si_type may be either "kcs", "smic", or "bt". If you leave it blank, it 393defaults to "kcs". 394 395If you specify addrs as non-zero for an interface, the driver will 396use the memory address given as the address of the device. This 397overrides si_ports. 398 399If you specify ports as non-zero for an interface, the driver will 400use the I/O port given as the device address. 401 402If you specify irqs as non-zero for an interface, the driver will 403attempt to use the given interrupt for the device. 404 405The other try... items disable discovery by their corresponding 406names. These are all enabled by default, set them to zero to disable 407them. The tryplatform disables openfirmware. 408 409The next three parameters have to do with register layout. The 410registers used by the interfaces may not appear at successive 411locations and they may not be in 8-bit registers. These parameters 412allow the layout of the data in the registers to be more precisely 413specified. 414 415The regspacings parameter give the number of bytes between successive 416register start addresses. For instance, if the regspacing is set to 4 417and the start address is 0xca2, then the address for the second 418register would be 0xca6. This defaults to 1. 419 420The regsizes parameter gives the size of a register, in bytes. The 421data used by IPMI is 8-bits wide, but it may be inside a larger 422register. This parameter allows the read and write type to specified. 423It may be 1, 2, 4, or 8. The default is 1. 424 425Since the register size may be larger than 32 bits, the IPMI data may not 426be in the lower 8 bits. The regshifts parameter give the amount to shift 427the data to get to the actual IPMI data. 428 429The slave_addrs specifies the IPMI address of the local BMC. This is 430usually 0x20 and the driver defaults to that, but in case it's not, it 431can be specified when the driver starts up. 432 433The force_ipmid parameter forcefully enables (if set to 1) or disables 434(if set to 0) the kernel IPMI daemon. Normally this is auto-detected 435by the driver, but systems with broken interrupts might need an enable, 436or users that don't want the daemon (don't need the performance, don't 437want the CPU hit) can disable it. 438 439If unload_when_empty is set to 1, the driver will be unloaded if it 440doesn't find any interfaces or all the interfaces fail to work. The 441default is one. Setting to 0 is useful with the hotmod, but is 442obviously only useful for modules. 443 444When compiled into the kernel, the parameters can be specified on the 445kernel command line as:: 446 447 ipmi_si.type=<type1>,<type2>... 448 ipmi_si.ports=<port1>,<port2>... ipmi_si.addrs=<addr1>,<addr2>... 449 ipmi_si.irqs=<irq1>,<irq2>... 450 ipmi_si.regspacings=<sp1>,<sp2>,... 451 ipmi_si.regsizes=<size1>,<size2>,... 452 ipmi_si.regshifts=<shift1>,<shift2>,... 453 ipmi_si.slave_addrs=<addr1>,<addr2>,... 454 ipmi_si.force_kipmid=<enable1>,<enable2>,... 455 ipmi_si.kipmid_max_busy_us=<ustime1>,<ustime2>,... 456 457It works the same as the module parameters of the same names. 458 459If your IPMI interface does not support interrupts and is a KCS or 460SMIC interface, the IPMI driver will start a kernel thread for the 461interface to help speed things up. This is a low-priority kernel 462thread that constantly polls the IPMI driver while an IPMI operation 463is in progress. The force_kipmid module parameter will all the user to 464force this thread on or off. If you force it off and don't have 465interrupts, the driver will run VERY slowly. Don't blame me, 466these interfaces suck. 467 468Unfortunately, this thread can use a lot of CPU depending on the 469interface's performance. This can waste a lot of CPU and cause 470various issues with detecting idle CPU and using extra power. To 471avoid this, the kipmid_max_busy_us sets the maximum amount of time, in 472microseconds, that kipmid will spin before sleeping for a tick. This 473value sets a balance between performance and CPU waste and needs to be 474tuned to your needs. Maybe, someday, auto-tuning will be added, but 475that's not a simple thing and even the auto-tuning would need to be 476tuned to the user's desired performance. 477 478The driver supports a hot add and remove of interfaces. This way, 479interfaces can be added or removed after the kernel is up and running. 480This is done using /sys/modules/ipmi_si/parameters/hotmod, which is a 481write-only parameter. You write a string to this interface. The string 482has the format:: 483 484 <op1>[:op2[:op3...]] 485 486The "op"s are:: 487 488 add|remove,kcs|bt|smic,mem|i/o,<address>[,<opt1>[,<opt2>[,...]]] 489 490You can specify more than one interface on the line. The "opt"s are:: 491 492 rsp=<regspacing> 493 rsi=<regsize> 494 rsh=<regshift> 495 irq=<irq> 496 ipmb=<ipmb slave addr> 497 498and these have the same meanings as discussed above. Note that you 499can also use this on the kernel command line for a more compact format 500for specifying an interface. Note that when removing an interface, 501only the first three parameters (si type, address type, and address) 502are used for the comparison. Any options are ignored for removing. 503 504The SMBus Driver (SSIF) 505----------------------- 506 507The SMBus driver allows up to 4 SMBus devices to be configured in the 508system. By default, the driver will only register with something it 509finds in DMI or ACPI tables. You can change this 510at module load time (for a module) with:: 511 512 modprobe ipmi_ssif.o 513 addr=<i2caddr1>[,<i2caddr2>[,...]] 514 adapter=<adapter1>[,<adapter2>[...]] 515 dbg=<flags1>,<flags2>... 516 slave_addrs=<addr1>,<addr2>,... 517 tryacpi=[0|1] trydmi=[0|1] 518 [dbg_probe=1] 519 alerts_broken 520 521The addresses are normal I2C addresses. The adapter is the string 522name of the adapter, as shown in /sys/class/i2c-adapter/i2c-<n>/name. 523It is *NOT* i2c-<n> itself. Also, the comparison is done ignoring 524spaces, so if the name is "This is an I2C chip" you can say 525adapter_name=ThisisanI2cchip. This is because it's hard to pass in 526spaces in kernel parameters. 527 528The debug flags are bit flags for each BMC found, they are: 529IPMI messages: 1, driver state: 2, timing: 4, I2C probe: 8 530 531The tryxxx parameters can be used to disable detecting interfaces 532from various sources. 533 534Setting dbg_probe to 1 will enable debugging of the probing and 535detection process for BMCs on the SMBusses. 536 537The slave_addrs specifies the IPMI address of the local BMC. This is 538usually 0x20 and the driver defaults to that, but in case it's not, it 539can be specified when the driver starts up. 540 541alerts_broken does not enable SMBus alert for SSIF. Otherwise SMBus 542alert will be enabled on supported hardware. 543 544Discovering the IPMI compliant BMC on the SMBus can cause devices on 545the I2C bus to fail. The SMBus driver writes a "Get Device ID" IPMI 546message as a block write to the I2C bus and waits for a response. 547This action can be detrimental to some I2C devices. It is highly 548recommended that the known I2C address be given to the SMBus driver in 549the smb_addr parameter unless you have DMI or ACPI data to tell the 550driver what to use. 551 552When compiled into the kernel, the addresses can be specified on the 553kernel command line as:: 554 555 ipmb_ssif.addr=<i2caddr1>[,<i2caddr2>[...]] 556 ipmi_ssif.adapter=<adapter1>[,<adapter2>[...]] 557 ipmi_ssif.dbg=<flags1>[,<flags2>[...]] 558 ipmi_ssif.dbg_probe=1 559 ipmi_ssif.slave_addrs=<addr1>[,<addr2>[...]] 560 ipmi_ssif.tryacpi=[0|1] ipmi_ssif.trydmi=[0|1] 561 562These are the same options as on the module command line. 563 564The I2C driver does not support non-blocking access or polling, so 565this driver cannod to IPMI panic events, extend the watchdog at panic 566time, or other panic-related IPMI functions without special kernel 567patches and driver modifications. You can get those at the openipmi 568web page. 569 570The driver supports a hot add and remove of interfaces through the I2C 571sysfs interface. 572 573Other Pieces 574------------ 575 576Get the detailed info related with the IPMI device 577-------------------------------------------------- 578 579Some users need more detailed information about a device, like where 580the address came from or the raw base device for the IPMI interface. 581You can use the IPMI smi_watcher to catch the IPMI interfaces as they 582come or go, and to grab the information, you can use the function 583ipmi_get_smi_info(), which returns the following structure:: 584 585 struct ipmi_smi_info { 586 enum ipmi_addr_src addr_src; 587 struct device *dev; 588 union { 589 struct { 590 void *acpi_handle; 591 } acpi_info; 592 } addr_info; 593 }; 594 595Currently special info for only for SI_ACPI address sources is 596returned. Others may be added as necessary. 597 598Note that the dev pointer is included in the above structure, and 599assuming ipmi_smi_get_info returns success, you must call put_device 600on the dev pointer. 601 602 603Watchdog 604-------- 605 606A watchdog timer is provided that implements the Linux-standard 607watchdog timer interface. It has three module parameters that can be 608used to control it:: 609 610 modprobe ipmi_watchdog timeout=<t> pretimeout=<t> action=<action type> 611 preaction=<preaction type> preop=<preop type> start_now=x 612 nowayout=x ifnum_to_use=n panic_wdt_timeout=<t> 613 614ifnum_to_use specifies which interface the watchdog timer should use. 615The default is -1, which means to pick the first one registered. 616 617The timeout is the number of seconds to the action, and the pretimeout 618is the amount of seconds before the reset that the pre-timeout panic will 619occur (if pretimeout is zero, then pretimeout will not be enabled). Note 620that the pretimeout is the time before the final timeout. So if the 621timeout is 50 seconds and the pretimeout is 10 seconds, then the pretimeout 622will occur in 40 second (10 seconds before the timeout). The panic_wdt_timeout 623is the value of timeout which is set on kernel panic, in order to let actions 624such as kdump to occur during panic. 625 626The action may be "reset", "power_cycle", or "power_off", and 627specifies what to do when the timer times out, and defaults to 628"reset". 629 630The preaction may be "pre_smi" for an indication through the SMI 631interface, "pre_int" for an indication through the SMI with an 632interrupts, and "pre_nmi" for a NMI on a preaction. This is how 633the driver is informed of the pretimeout. 634 635The preop may be set to "preop_none" for no operation on a pretimeout, 636"preop_panic" to set the preoperation to panic, or "preop_give_data" 637to provide data to read from the watchdog device when the pretimeout 638occurs. A "pre_nmi" setting CANNOT be used with "preop_give_data" 639because you can't do data operations from an NMI. 640 641When preop is set to "preop_give_data", one byte comes ready to read 642on the device when the pretimeout occurs. Select and fasync work on 643the device, as well. 644 645If start_now is set to 1, the watchdog timer will start running as 646soon as the driver is loaded. 647 648If nowayout is set to 1, the watchdog timer will not stop when the 649watchdog device is closed. The default value of nowayout is true 650if the CONFIG_WATCHDOG_NOWAYOUT option is enabled, or false if not. 651 652When compiled into the kernel, the kernel command line is available 653for configuring the watchdog:: 654 655 ipmi_watchdog.timeout=<t> ipmi_watchdog.pretimeout=<t> 656 ipmi_watchdog.action=<action type> 657 ipmi_watchdog.preaction=<preaction type> 658 ipmi_watchdog.preop=<preop type> 659 ipmi_watchdog.start_now=x 660 ipmi_watchdog.nowayout=x 661 ipmi_watchdog.panic_wdt_timeout=<t> 662 663The options are the same as the module parameter options. 664 665The watchdog will panic and start a 120 second reset timeout if it 666gets a pre-action. During a panic or a reboot, the watchdog will 667start a 120 timer if it is running to make sure the reboot occurs. 668 669Note that if you use the NMI preaction for the watchdog, you MUST NOT 670use the nmi watchdog. There is no reasonable way to tell if an NMI 671comes from the IPMI controller, so it must assume that if it gets an 672otherwise unhandled NMI, it must be from IPMI and it will panic 673immediately. 674 675Once you open the watchdog timer, you must write a 'V' character to the 676device to close it, or the timer will not stop. This is a new semantic 677for the driver, but makes it consistent with the rest of the watchdog 678drivers in Linux. 679 680 681Panic Timeouts 682-------------- 683 684The OpenIPMI driver supports the ability to put semi-custom and custom 685events in the system event log if a panic occurs. if you enable the 686'Generate a panic event to all BMCs on a panic' option, you will get 687one event on a panic in a standard IPMI event format. If you enable 688the 'Generate OEM events containing the panic string' option, you will 689also get a bunch of OEM events holding the panic string. 690 691 692The field settings of the events are: 693 694* Generator ID: 0x21 (kernel) 695* EvM Rev: 0x03 (this event is formatting in IPMI 1.0 format) 696* Sensor Type: 0x20 (OS critical stop sensor) 697* Sensor #: The first byte of the panic string (0 if no panic string) 698* Event Dir | Event Type: 0x6f (Assertion, sensor-specific event info) 699* Event Data 1: 0xa1 (Runtime stop in OEM bytes 2 and 3) 700* Event data 2: second byte of panic string 701* Event data 3: third byte of panic string 702 703See the IPMI spec for the details of the event layout. This event is 704always sent to the local management controller. It will handle routing 705the message to the right place 706 707Other OEM events have the following format: 708 709* Record ID (bytes 0-1): Set by the SEL. 710* Record type (byte 2): 0xf0 (OEM non-timestamped) 711* byte 3: The slave address of the card saving the panic 712* byte 4: A sequence number (starting at zero) 713 The rest of the bytes (11 bytes) are the panic string. If the panic string 714 is longer than 11 bytes, multiple messages will be sent with increasing 715 sequence numbers. 716 717Because you cannot send OEM events using the standard interface, this 718function will attempt to find an SEL and add the events there. It 719will first query the capabilities of the local management controller. 720If it has an SEL, then they will be stored in the SEL of the local 721management controller. If not, and the local management controller is 722an event generator, the event receiver from the local management 723controller will be queried and the events sent to the SEL on that 724device. Otherwise, the events go nowhere since there is nowhere to 725send them. 726 727 728Poweroff 729-------- 730 731If the poweroff capability is selected, the IPMI driver will install 732a shutdown function into the standard poweroff function pointer. This 733is in the ipmi_poweroff module. When the system requests a powerdown, 734it will send the proper IPMI commands to do this. This is supported on 735several platforms. 736 737There is a module parameter named "poweroff_powercycle" that may 738either be zero (do a power down) or non-zero (do a power cycle, power 739the system off, then power it on in a few seconds). Setting 740ipmi_poweroff.poweroff_control=x will do the same thing on the kernel 741command line. The parameter is also available via the proc filesystem 742in /proc/sys/dev/ipmi/poweroff_powercycle. Note that if the system 743does not support power cycling, it will always do the power off. 744 745The "ifnum_to_use" parameter specifies which interface the poweroff 746code should use. The default is -1, which means to pick the first one 747registered. 748 749Note that if you have ACPI enabled, the system will prefer using ACPI to 750power off. 751