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author | Stewart Smith <stewart@linux.vnet.ibm.com> | 2016-07-27 17:43:04 +1000 |
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committer | Stewart Smith <stewart@linux.vnet.ibm.com> | 2016-08-02 17:31:12 +1000 |
commit | cce80be2fc7d9114ea0000349cc52f0947ea00f1 (patch) | |
tree | 14670835d17bd6967b2d09c9973fb0e2dd88feca /doc/console-log.rst | |
parent | 68bf986c37252eed2e8fa3db07de02bbd47ff97a (diff) | |
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doc/*.txt: rename .txt to .rst
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
Diffstat (limited to 'doc/console-log.rst')
-rw-r--r-- | doc/console-log.rst | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/doc/console-log.rst b/doc/console-log.rst new file mode 100644 index 0000000..fbdd33b --- /dev/null +++ b/doc/console-log.rst @@ -0,0 +1,60 @@ +SkiBoot Console Log +------------------- + +Skiboot maintains a circular textual log buffer in memory. + +It can be accessed using any debugging method that can peek at +memory contents. While the debug_descriptor does hold the location +of the memory console, we're pretty keen on keeping its location +static. + +Events are logged in the following format: +[timebase,log_level] message + +You should use the new prlog() call for any log message and set the +log level/priority appropriately. + +printf() is mapped to PR_PRINTF and should be phased out and replaced +with prlog() calls. + +See timebase.h for full timebase explanation. + +Log level from skiboot.h: +#define PR_EMERG 0 +#define PR_ALERT 1 +#define PR_CRIT 2 +#define PR_ERR 3 +#define PR_WARNING 4 +#define PR_NOTICE 5 +#define PR_PRINTF PR_NOTICE +#define PR_INFO 6 +#define PR_DEBUG 7 +#define PR_TRACE 8 +#define PR_INSANE 9 + +The console_log_levels byte in the debug_descriptor controls what +messages are written to any console drivers (e.g. fsp, uart) and +what level is just written to the in memory console (or not at all). + +This enables (advanced) users to vary what level of output they want +at runtime in the memory console and through console drivers (fsp/uart) + +You can vary two things by poking in the debug descriptor: +a) what log level is printed at all + e.g. only turn on PR_TRACE at specific points during runtime +b) what log level goes out the fsp/uart console + defaults to PR_PRINTF + +We use two 4bit numbers (1 byte) for this in debug descriptor (saving +some space, not needlessly wasting space that we may want in future). + +The default is 0x75 (7=PR_DEBUG to in memory console, 5=PR_PRINTF to drivers + +If you write 0x77 you will get debug info on uart/fsp console as +well as in memory. If you write 0x95 you get PR_INSANE in memory but +still only PR_NOTICE through drivers. + +People who write something like 0x1f will get a very quiet boot indeed. + + + |