From 448eea9037e8ddfd28b409f6db2330cf17013031 Mon Sep 17 00:00:00 2001 From: Jeremy Kerr Date: Wed, 1 Jun 2016 17:14:00 +0800 Subject: doc: Add initial BMC interactions document This change adds a minimal document to describe some of the OPAL <--> BMC interactions supported by skiboot. Signed-off-by: Jeremy Kerr Reviewed-by: Joel Stanley Signed-off-by: Stewart Smith --- doc/bmc.txt | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 doc/bmc.txt (limited to 'doc') diff --git a/doc/bmc.txt b/doc/bmc.txt new file mode 100644 index 00000000..78c3b299 --- /dev/null +++ b/doc/bmc.txt @@ -0,0 +1,57 @@ +OPAL <--> BMC interactions +========================== + +This document provides information about some of the user-visible interactions +that skiboot performs with the BMC. + +IPMI sensors +------------ + +OPAL will interact with a few IPMI sensors during the boot process. These +are: + + * Boot Count [type 0xc3: OEM reserved] + * FW Boot progress [type 0x0f: System Firmware Progress] + +Boot Count: assertion type. When OPAL reaches a late stage of boot, it sets the +boot count sensor to 0x02. This is intended to allow the BMC detect a failed +or aborted boot, for switching to a known-good firmware image. + +FW Boot Progress: assertion type. During boot, skiboot will update this sensor +to one of the IPMI-defined progress codes. The codes use by skiboot are: + + * PCI Resource configuration (0x01) + - asserted as the PCI devices have been probed and resources allocated + + * Motherboard init (0x14) + - asserted as the platform-specific components have been initialised + + * OS boot (0x13) + - asserted after skiboot has loaded the PAYLOAD image, and is about to + boot it. + +Chassis control messages +------------------------ + +OPAL uses chassis control messages to instruct the BMC to remove power from +the host. These messages are sent during graceful reboot and shutdown processes +initiated by the host. + +For a BMC-initiated graceful power-down (or reboot), the BMC is expected to send +an OEM-defined SEL message, using a SMS_ATN to trigger a BMC-to-host +notification. This SEL has a type of 0xc0, and command of 0x04. The data0 field +of the SEL indicates shutdown (0x0) or reboot (0x1). + + +Watchdog support +---------------- + +OPAL supports a BMC watchdog during the boot process. This will be disabled +before entering the OS. + + +Real-time clock +--------------- + +On platforms where a real-time-clock is not available, skiboot may use the +IPMI SEL Time as a real-time-clock device. -- cgit v1.2.1