Documentation/devicetree/bindings/reserved-memory/ramoops.txt

   1 Ramoops oops/panic logger
   2 =========================
   3
   4 ramoops provides persistent RAM storage for oops and panics, so they can be
   5 recovered after a reboot. This is a child-node of "/reserved-memory", and
   6 is named "ramoops" after the backend, rather than "pstore" which is the
   7 subsystem.
   8
   9 Parts of this storage may be set aside for other persistent log buffers, such
  10 as kernel log messages, or for optional ECC error-correction data.  The total
  11 size of these optional buffers must fit in the reserved region.
  12
  13 Any remaining space will be used for a circular buffer of oops and panic
  14 records.  These records have a configurable size, with a size of 0 indicating
  15 that they should be disabled.
  16
  17 At least one of "record-size", "console-size", "ftrace-size", or "pmsg-size"
  18 must be set non-zero, but are otherwise optional as listed below.
  19
  20
  21 Required properties:
  22
  23 - compatible: must be "ramoops"
  24
  25 - reg: region of memory that is preserved between reboots
  26
  27
  28 Optional properties:
  29
  30 - ecc-size: enables ECC support and specifies ECC buffer size in bytes
  31   (defaults to 0: no ECC)
  32
  33 - record-size: maximum size in bytes of each kmsg dump.
  34   (defaults to 0: disabled)
  35
  36 - console-size: size in bytes of log buffer reserved for kernel messages
  37   (defaults to 0: disabled)
  38
  39 - ftrace-size: size in bytes of log buffer reserved for function tracing and
  40   profiling (defaults to 0: disabled)
  41
  42 - pmsg-size: size in bytes of log buffer reserved for userspace messages
  43   (defaults to 0: disabled)
  44
  45 - unbuffered: if present, use unbuffered mappings to map the reserved region
  46   (defaults to buffered mappings)
  47
  48 - max-reason: if present, sets maximum type of kmsg dump reasons to store
  49   (defaults to 2: log Oopses and Panics). This can be set to INT_MAX to
  50   store all kmsg dumps. See include/linux/kmsg_dump.h KMSG_DUMP_* for other
  51   kmsg dump reason values. Setting this to 0 (KMSG_DUMP_UNDEF), means the
  52   reason filtering will be controlled by the printk.always_kmsg_dump boot
  53   param: if unset, it will be KMSG_DUMP_OOPS, otherwise KMSG_DUMP_MAX.
  54
  55 - no-dump-oops: deprecated, use max_reason instead. If present, and
  56   max_reason is not specified, it is equivalent to max_reason = 1
  57   (KMSG_DUMP_PANIC).
  58
  59 - flags: if present, pass ramoops behavioral flags (defaults to 0,
  60   see include/linux/pstore_ram.h RAMOOPS_FLAG_* for flag values).