- Fix document title;
- use quote blocks where needed;
- use monotonic fonts for config options and file names;
- adjust whitespaces and blank lines;
- add it to the user's book.
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
---
Documentation/ramoops.txt | 86 ++++++++++++++++++++++++++---------------------
1 file changed, 47 insertions(+), 39 deletions(-)
diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
index 26b9f31cf65a..7eaf1e71c083 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -5,34 +5,37 @@ Sergiu Iordache <sergiu@xxxxxxxxxxxx>
Updated: 17 November 2011
-0. Introduction
+Introduction
+------------
Ramoops is an oops/panic logger that writes its logs to RAM before the system
crashes. It works by logging oopses and panics in a circular buffer. Ramoops
needs a system with persistent RAM so that the content of that area can
survive after a restart.
-1. Ramoops concepts
+Ramoops concepts
+----------------
Ramoops uses a predefined memory area to store the dump. The start and size
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).
-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
-pgprot_noncached, which only works on some platforms. This is because pstore
+ * ``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).
+
+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
+``pgprot_noncached``, which only works on some platforms. This is because pstore
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.
-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
+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
information.
-Dumping both oopses and panics can be done by setting 1 in the "dump_oops"
+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.
The module uses a counter to record multiple dumps but the counter gets reset
@@ -43,7 +46,8 @@ This might be useful when a hardware reset was used to bring the machine back
to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat
corrupt, but usually it is restorable.
-2. Setting the parameters
+Setting the parameters
+----------------------
Setting the ramoops parameters can be done in several different manners:
@@ -52,12 +56,13 @@ Setting the ramoops parameters can be done in several different manners:
boot and then use the reserved memory for ramoops. For example, assuming a
machine with > 128 MB of memory, the following kernel command line will tell
the kernel to use only the first 128 MB of memory, and place ECC-protected
- ramoops region at 128 MB boundary:
- "mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1"
+ ramoops region at 128 MB boundary::
+
+ mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1
B. Use Device Tree bindings, as described in
- Documentation/device-tree/bindings/reserved-memory/ramoops.txt.
- For example:
+ ``Documentation/device-tree/bindings/reserved-memory/ramoops.txt``.
+ For example::
reserved-memory {
#address-cells = <2>;
@@ -73,60 +78,63 @@ Setting the ramoops parameters can be done in several different manners:
};
C. Use a platform device and set the platform data. The parameters can then
- be set through that platform data. An example of doing that is:
+ be set through that platform data. An example of doing that is::
-#include <linux/pstore_ram.h>
-[...]
+ #include <linux/pstore_ram.h>
+ [...]
-static struct ramoops_platform_data ramoops_data = {
+ static struct ramoops_platform_data ramoops_data = {
.mem_size = <...>,
.mem_address = <...>,
.mem_type = <...>,
.record_size = <...>,
.dump_oops = <...>,
.ecc = <...>,
-};
+ };
-static struct platform_device ramoops_dev = {
+ static struct platform_device ramoops_dev = {
.name = "ramoops",
.dev = {
.platform_data = &ramoops_data,
},
-};
+ };
-[... inside a function ...]
-int ret;
+ [... inside a function ...]
+ int ret;
-ret = platform_device_register(&ramoops_dev);
-if (ret) {
+ ret = platform_device_register(&ramoops_dev);
+ if (ret) {
printk(KERN_ERR "unable to register platform device\n");
return ret;
-}
+ }
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.:
+very early in the architecture code, e.g.::
-#include <linux/memblock.h>
+ #include <linux/memblock.h>
-memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size);
+ memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size);
-3. Dump format
+Dump format
+-----------
-The data dump begins with a header, currently defined as "====" followed by a
+The data dump begins with a header, currently defined as ``====`` followed by a
timestamp and a new line. The dump then continues with the actual data.
-4. Reading the data
+Reading the data
+----------------
The dump data can be read from the pstore filesystem. The format for these
-files is "dmesg-ramoops-N", where N is the record number in memory. To delete
+files is ``dmesg-ramoops-N``, where N is the record number in memory. To delete
a stored record from RAM, simply unlink the respective pstore file.
-5. Persistent function tracing
+Persistent function tracing
+---------------------------
Persistent function tracing might be useful for debugging software or hardware
-related hangs. The functions call chain log is stored in a "ftrace-ramoops"
-file. Here is an example of usage:
+related hangs. The functions call chain log is stored in a ``ftrace-ramoops``
+file. Here is an example of usage::
# mount -t debugfs debugfs /sys/kernel/debug/
# echo 1 > /sys/kernel/debug/pstore/record_ftrace
--
2.7.4
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