[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / watchdog / hpwdt.txt

Last reviewed: 06/02/2009

                     HP iLO2 NMI Watchdog Driver
              NMI sourcing for iLO2 based ProLiant Servers
                     Documentation and Driver by
              Thomas Mingarelli <thomas.mingarelli@hp.com>

 The HP iLO2 NMI Watchdog driver is a kernel module that provides basic
 watchdog functionality and the added benefit of NMI sourcing. Both the
 watchdog functionality and the NMI sourcing capability need to be enabled
 by the user. Remember that the two modes are not dependent on one another.
 A user can have the NMI sourcing without the watchdog timer and vice-versa.

 Watchdog functionality is enabled like any other common watchdog driver. That
 is, an application needs to be started that kicks off the watchdog timer. A
 basic application exists in the Documentation/watchdog/src directory called
 watchdog-test.c. Simply compile the C file and kick it off. If the system
 gets into a bad state and hangs, the HP ProLiant iLO 2 timer register will
 not be updated in a timely fashion and a hardware system reset (also known as
 an Automatic Server Recovery (ASR)) event will occur.

 The hpwdt driver also has four (4) module parameters. They are the following:

 soft_margin - allows the user to set the watchdog timer value
 allow_kdump - allows the user to save off a kernel dump image after an NMI
 nowayout    - basic watchdog parameter that does not allow the timer to
               be restarted or an impending ASR to be escaped.
 priority    - determines whether or not the hpwdt driver is first on the
               die_notify list to handle NMIs or last. The default value
               for this module parameter is 0 or LAST. If the user wants to
               enable NMI sourcing then reload the hpwdt driver with
               priority=1 (and boot with nmi_watchdog=0).

 NOTE: More information about watchdog drivers in general, including the ioctl
       interface to /dev/watchdog can be found in
       Documentation/watchdog/watchdog-api.txt and Documentation/IPMI.txt.

 The priority parameter was introduced due to other kernel software that relied
 on handling NMIs (like oprofile). Keeping hpwdt's priority at 0 (or LAST)
 enables the users of NMIs for non critical events to be work as expected.

 The NMI sourcing capability is disabled by default due to the inability to
 distinguish between "NMI Watchdog Ticks" and "HW generated NMI events" in the
 Linux kernel. What this means is that the hpwdt nmi handler code is called
 each time the NMI signal fires off. This could amount to several thousands of
 NMIs in a matter of seconds. If a user sees the Linux kernel's "dazed and
 confused" message in the logs or if the system gets into a hung state, then
 the hpwdt driver can be reloaded with the "priority" module parameter set
 (priority=1).

 1. If the kernel has not been booted with nmi_watchdog turned off then
    edit /boot/grub/menu.lst and place the nmi_watchdog=0 at the end of the
    currently booting kernel line.
 2. reboot the sever
 3. Once the system comes up perform a rmmod hpwdt
 4. insmod /lib/modules/`uname -r`/kernel/drivers/char/watchdog/hpwdt.ko priority=1

 Now, the hpwdt can successfully receive and source the NMI and provide a log
 message that details the reason for the NMI (as determined by the HP BIOS).

 Below is a list of NMIs the HP BIOS understands along with the associated
 code (reason):

	No source found                00h

	Uncorrectable Memory Error     01h

	ASR NMI                        1Bh

	PCI Parity Error               20h

	NMI Button Press               27h

	SB_BUS_NMI                     28h

	ILO Doorbell NMI               29h

	ILO IOP NMI                    2Ah

	ILO Watchdog NMI               2Bh

	Proc Throt NMI                 2Ch

	Front Side Bus NMI             2Dh

	PCI Express Error              2Fh

	DMA controller NMI             30h

	Hypertransport/CSI Error       31h


 -- Tom Mingarelli
    (thomas.mingarelli@hp.com)
Commit	Line	Data
47bece87 TM	1	Last reviewed: 06/02/2009
	2
	3	HP iLO2 NMI Watchdog Driver
	4	NMI sourcing for iLO2 based ProLiant Servers
	5	Documentation and Driver by
	6	Thomas Mingarelli <thomas.mingarelli@hp.com>
	7
	8	The HP iLO2 NMI Watchdog driver is a kernel module that provides basic
	9	watchdog functionality and the added benefit of NMI sourcing. Both the
	10	watchdog functionality and the NMI sourcing capability need to be enabled
25985edc	11	by the user. Remember that the two modes are not dependent on one another.
47bece87 TM	12	A user can have the NMI sourcing without the watchdog timer and vice-versa.
	13
	14	Watchdog functionality is enabled like any other common watchdog driver. That
	15	is, an application needs to be started that kicks off the watchdog timer. A
	16	basic application exists in the Documentation/watchdog/src directory called
	17	watchdog-test.c. Simply compile the C file and kick it off. If the system
	18	gets into a bad state and hangs, the HP ProLiant iLO 2 timer register will
	19	not be updated in a timely fashion and a hardware system reset (also known as
	20	an Automatic Server Recovery (ASR)) event will occur.
	21
44df7535	22	The hpwdt driver also has four (4) module parameters. They are the following:
47bece87 TM	23
	24	soft_margin - allows the user to set the watchdog timer value
	25	allow_kdump - allows the user to save off a kernel dump image after an NMI
	26	nowayout - basic watchdog parameter that does not allow the timer to
	27	be restarted or an impending ASR to be escaped.
44df7535 TM	28	priority - determines whether or not the hpwdt driver is first on the
	29	die_notify list to handle NMIs or last. The default value
	30	for this module parameter is 0 or LAST. If the user wants to
	31	enable NMI sourcing then reload the hpwdt driver with
	32	priority=1 (and boot with nmi_watchdog=0).
47bece87 TM	33
	34	NOTE: More information about watchdog drivers in general, including the ioctl
	35	interface to /dev/watchdog can be found in
	36	Documentation/watchdog/watchdog-api.txt and Documentation/IPMI.txt.
	37
44df7535 TM	38	The priority parameter was introduced due to other kernel software that relied
	39	on handling NMIs (like oprofile). Keeping hpwdt's priority at 0 (or LAST)
	40	enables the users of NMIs for non critical events to be work as expected.
	41
	42	The NMI sourcing capability is disabled by default due to the inability to
47bece87 TM	43	distinguish between "NMI Watchdog Ticks" and "HW generated NMI events" in the
	44	Linux kernel. What this means is that the hpwdt nmi handler code is called
	45	each time the NMI signal fires off. This could amount to several thousands of
	46	NMIs in a matter of seconds. If a user sees the Linux kernel's "dazed and
	47	confused" message in the logs or if the system gets into a hung state, then
44df7535 TM	48	the hpwdt driver can be reloaded with the "priority" module parameter set
44df7535 TM	49	(priority=1).
47bece87 TM	50
	51	1. If the kernel has not been booted with nmi_watchdog turned off then
	52	edit /boot/grub/menu.lst and place the nmi_watchdog=0 at the end of the
	53	currently booting kernel line.
	54	2. reboot the sever
44df7535 TM	55	3. Once the system comes up perform a rmmod hpwdt
44df7535 TM	56	4. insmod /lib/modules/`uname -r`/kernel/drivers/char/watchdog/hpwdt.ko priority=1
47bece87 TM	57
	58	Now, the hpwdt can successfully receive and source the NMI and provide a log
	59	message that details the reason for the NMI (as determined by the HP BIOS).
	60
	61	Below is a list of NMIs the HP BIOS understands along with the associated
	62	code (reason):
	63
	64	No source found 00h
	65
	66	Uncorrectable Memory Error 01h
	67
	68	ASR NMI 1Bh
	69
	70	PCI Parity Error 20h
	71
	72	NMI Button Press 27h
	73
	74	SB_BUS_NMI 28h
	75
	76	ILO Doorbell NMI 29h
	77
	78	ILO IOP NMI 2Ah
	79
	80	ILO Watchdog NMI 2Bh
	81
	82	Proc Throt NMI 2Ch
	83
	84	Front Side Bus NMI 2Dh
	85
	86	PCI Express Error 2Fh
	87
	88	DMA controller NMI 30h
	89
	90	Hypertransport/CSI Error 31h
	91
	92
	93
	94	-- Tom Mingarelli
	95	(thomas.mingarelli@hp.com)