ramoops: Split ftrace buffer space into per-CPU zones

[linux-2.6-block.git] / Documentation / devicetree / bindings / reserved-memory / ramoops.txt

Ramoops oops/panic logger
=========================

ramoops provides persistent RAM storage for oops and panics, so they can be
recovered after a reboot. This is a child-node of "/reserved-memory", and
is named "ramoops" after the backend, rather than "pstore" which is the
subsystem.

Parts of this storage may be set aside for other persistent log buffers, such
as kernel log messages, or for optional ECC error-correction data.  The total
size of these optional buffers must fit in the reserved region.

Any remaining space will be used for a circular buffer of oops and panic
records.  These records have a configurable size, with a size of 0 indicating
that they should be disabled.

At least one of "record-size", "console-size", "ftrace-size", or "pmsg-size"
must be set non-zero, but are otherwise optional as listed below.


Required properties:

- compatible: must be "ramoops"

- reg: region of memory that is preserved between reboots


Optional properties:

- ecc-size: enables ECC support and specifies ECC buffer size in bytes
  (defaults to 0: no ECC)

- record-size: maximum size in bytes of each dump done on oops/panic
  (defaults to 0: disabled)

- console-size: size in bytes of log buffer reserved for kernel messages
  (defaults to 0: disabled)

- ftrace-size: size in bytes of log buffer reserved for function tracing and
  profiling (defaults to 0: disabled)

- pmsg-size: size in bytes of log buffer reserved for userspace messages
  (defaults to 0: disabled)

- unbuffered: if present, use unbuffered mappings to map the reserved region
  (defaults to buffered mappings)

- no-dump-oops: if present, only dump panics (defaults to panics and oops)

- flags: if present, pass ramoops behavioral flags (defaults to 0,
  see include/linux/pstore_ram.h RAMOOPS_FLAG_* for flag values).