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Diffstat (limited to 'Documentation/admin-guide/ramoops.rst')
| -rw-r--r-- | Documentation/admin-guide/ramoops.rst | 35 |
1 files changed, 28 insertions, 7 deletions
diff --git a/Documentation/admin-guide/ramoops.rst b/Documentation/admin-guide/ramoops.rst index 6dbcc5481000..2eabef31220d 100644 --- a/Documentation/admin-guide/ramoops.rst +++ b/Documentation/admin-guide/ramoops.rst @@ -3,7 +3,7 @@ Ramoops oops/panic logger Sergiu Iordache <sergiu@chromium.org> -Updated: 17 November 2011 +Updated: 10 Feb 2021 Introduction ------------ @@ -22,7 +22,9 @@ and type of the memory area are set using three variables: * ``mem_address`` for the start * ``mem_size`` for the size. The memory size will be rounded down to a power of two. - * ``mem_type`` to specifiy if the memory type (default is pgprot_writecombine). + * ``mem_type`` to specify if the memory type (default is pgprot_writecombine). + * ``mem_name`` to specify a memory region defined by ``reserve_mem`` command + line parameter. Typically the default value of ``mem_type=0`` should be used as that sets the pstore mapping to pgprot_writecombine. Setting ``mem_type=1`` attempts to use @@ -30,13 +32,21 @@ mapping to pgprot_writecombine. Setting ``mem_type=1`` attempts to use depends on atomic operations. At least on ARM, pgprot_noncached causes the memory to be mapped strongly ordered, and atomic operations on strongly ordered memory are implementation defined, and won't work on many ARMs such as omaps. +Setting ``mem_type=2`` attempts to treat the memory region as normal memory, +which enables full cache on it. This can improve the performance. The memory area is divided into ``record_size`` chunks (also rounded down to -power of two) and each oops/panic writes a ``record_size`` chunk of +power of two) and each kmesg dump writes a ``record_size`` chunk of information. -Dumping both oopses and panics can be done by setting 1 in the ``dump_oops`` -variable while setting 0 in that variable dumps only the panics. +Limiting which kinds of kmsg dumps are stored can be controlled via +the ``max_reason`` value, as defined in include/linux/kmsg_dump.h's +``enum kmsg_dump_reason``. For example, to store both Oopses and Panics, +``max_reason`` should be set to 2 (KMSG_DUMP_OOPS), to store only Panics +``max_reason`` should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0 +(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the +``printk.always_kmsg_dump`` boot param: if unset, it'll be KMSG_DUMP_OOPS, +otherwise KMSG_DUMP_MAX. The module uses a counter to record multiple dumps but the counter gets reset on restart (i.e. new dumps after the restart will overwrite old ones). @@ -61,7 +71,7 @@ Setting the ramoops parameters can be done in several different manners: mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1 B. Use Device Tree bindings, as described in - ``Documentation/devicetree/bindings/reserved-memory/ramoops.txt``. + ``Documentation/devicetree/bindings/reserved-memory/ramoops.yaml``. For example:: reserved-memory { @@ -90,7 +100,7 @@ Setting the ramoops parameters can be done in several different manners: .mem_address = <...>, .mem_type = <...>, .record_size = <...>, - .dump_oops = <...>, + .max_reason = <...>, .ecc = <...>, }; @@ -110,6 +120,17 @@ Setting the ramoops parameters can be done in several different manners: return ret; } + D. Using a region of memory reserved via ``reserve_mem`` command line + parameter. The address and size will be defined by the ``reserve_mem`` + parameter. Note, that ``reserve_mem`` may not always allocate memory + in the same location, and cannot be relied upon. Testing will need + to be done, and it may not work on every machine, nor every kernel. + Consider this a "best effort" approach. The ``reserve_mem`` option + takes a size, alignment and name as arguments. The name is used + to map the memory to a label that can be retrieved by ramoops. + + reserve_mem=2M:4096:oops ramoops.mem_name=oops + You can specify either RAM memory or peripheral devices' memory. However, when specifying RAM, be sure to reserve the memory by issuing memblock_reserve() very early in the architecture code, e.g.:: |