| ACPICA Trace Facility |
| |
| Copyright (C) 2015, Intel Corporation |
| Author: Lv Zheng <lv.zheng@intel.com> |
| |
| |
| Abstract: |
| |
| This document describes the functions and the interfaces of the method |
| tracing facility. |
| |
| 1. Functionalities and usage examples: |
| |
| ACPICA provides method tracing capability. And two functions are |
| currently implemented using this capability. |
| |
| A. Log reducer |
| ACPICA subsystem provides debugging outputs when CONFIG_ACPI_DEBUG is |
| enabled. The debugging messages which are deployed via |
| ACPI_DEBUG_PRINT() macro can be reduced at 2 levels - per-component |
| level (known as debug layer, configured via |
| /sys/module/acpi/parameters/debug_layer) and per-type level (known as |
| debug level, configured via /sys/module/acpi/parameters/debug_level). |
| |
| But when the particular layer/level is applied to the control method |
| evaluations, the quantity of the debugging outputs may still be too |
| large to be put into the kernel log buffer. The idea thus is worked out |
| to only enable the particular debug layer/level (normally more detailed) |
| logs when the control method evaluation is started, and disable the |
| detailed logging when the control method evaluation is stopped. |
| |
| The following command examples illustrate the usage of the "log reducer" |
| functionality: |
| a. Filter out the debug layer/level matched logs when control methods |
| are being evaluated: |
| # cd /sys/module/acpi/parameters |
| # echo "0xXXXXXXXX" > trace_debug_layer |
| # echo "0xYYYYYYYY" > trace_debug_level |
| # echo "enable" > trace_state |
| b. Filter out the debug layer/level matched logs when the specified |
| control method is being evaluated: |
| # cd /sys/module/acpi/parameters |
| # echo "0xXXXXXXXX" > trace_debug_layer |
| # echo "0xYYYYYYYY" > trace_debug_level |
| # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name |
| # echo "method" > /sys/module/acpi/parameters/trace_state |
| c. Filter out the debug layer/level matched logs when the specified |
| control method is being evaluated for the first time: |
| # cd /sys/module/acpi/parameters |
| # echo "0xXXXXXXXX" > trace_debug_layer |
| # echo "0xYYYYYYYY" > trace_debug_level |
| # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name |
| # echo "method-once" > /sys/module/acpi/parameters/trace_state |
| Where: |
| 0xXXXXXXXX/0xYYYYYYYY: Refer to Documentation/acpi/debug.txt for |
| possible debug layer/level masking values. |
| \PPPP.AAAA.TTTT.HHHH: Full path of a control method that can be found |
| in the ACPI namespace. It needn't be an entry |
| of a control method evaluation. |
| |
| B. AML tracer |
| |
| There are special log entries added by the method tracing facility at |
| the "trace points" the AML interpreter starts/stops to execute a control |
| method, or an AML opcode. Note that the format of the log entries are |
| subject to change: |
| [ 0.186427] exdebug-0398 ex_trace_point : Method Begin [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution. |
| [ 0.186630] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905c88:If] execution. |
| [ 0.186820] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905cc0:LEqual] execution. |
| [ 0.187010] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905a20:-NamePath-] execution. |
| [ 0.187214] exdebug-0398 ex_trace_point : Opcode End [0xf5905a20:-NamePath-] execution. |
| [ 0.187407] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905f60:One] execution. |
| [ 0.187594] exdebug-0398 ex_trace_point : Opcode End [0xf5905f60:One] execution. |
| [ 0.187789] exdebug-0398 ex_trace_point : Opcode End [0xf5905cc0:LEqual] execution. |
| [ 0.187980] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905cc0:Return] execution. |
| [ 0.188146] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905f60:One] execution. |
| [ 0.188334] exdebug-0398 ex_trace_point : Opcode End [0xf5905f60:One] execution. |
| [ 0.188524] exdebug-0398 ex_trace_point : Opcode End [0xf5905cc0:Return] execution. |
| [ 0.188712] exdebug-0398 ex_trace_point : Opcode End [0xf5905c88:If] execution. |
| [ 0.188903] exdebug-0398 ex_trace_point : Method End [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution. |
| |
| Developers can utilize these special log entries to track the AML |
| interpretion, thus can aid issue debugging and performance tuning. Note |
| that, as the "AML tracer" logs are implemented via ACPI_DEBUG_PRINT() |
| macro, CONFIG_ACPI_DEBUG is also required to be enabled for enabling |
| "AML tracer" logs. |
| |
| The following command examples illustrate the usage of the "AML tracer" |
| functionality: |
| a. Filter out the method start/stop "AML tracer" logs when control |
| methods are being evaluated: |
| # cd /sys/module/acpi/parameters |
| # echo "0x80" > trace_debug_layer |
| # echo "0x10" > trace_debug_level |
| # echo "enable" > trace_state |
| b. Filter out the method start/stop "AML tracer" when the specified |
| control method is being evaluated: |
| # cd /sys/module/acpi/parameters |
| # echo "0x80" > trace_debug_layer |
| # echo "0x10" > trace_debug_level |
| # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name |
| # echo "method" > trace_state |
| c. Filter out the method start/stop "AML tracer" logs when the specified |
| control method is being evaluated for the first time: |
| # cd /sys/module/acpi/parameters |
| # echo "0x80" > trace_debug_layer |
| # echo "0x10" > trace_debug_level |
| # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name |
| # echo "method-once" > trace_state |
| d. Filter out the method/opcode start/stop "AML tracer" when the |
| specified control method is being evaluated: |
| # cd /sys/module/acpi/parameters |
| # echo "0x80" > trace_debug_layer |
| # echo "0x10" > trace_debug_level |
| # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name |
| # echo "opcode" > trace_state |
| e. Filter out the method/opcode start/stop "AML tracer" when the |
| specified control method is being evaluated for the first time: |
| # cd /sys/module/acpi/parameters |
| # echo "0x80" > trace_debug_layer |
| # echo "0x10" > trace_debug_level |
| # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name |
| # echo "opcode-opcode" > trace_state |
| |
| Note that all above method tracing facility related module parameters can |
| be used as the boot parameters, for example: |
| acpi.trace_debug_layer=0x80 acpi.trace_debug_level=0x10 \ |
| acpi.trace_method_name=\_SB.LID0._LID acpi.trace_state=opcode-once |
| |
| 2. Interface descriptions: |
| |
| All method tracing functions can be configured via ACPI module |
| parameters that are accessible at /sys/module/acpi/parameters/: |
| |
| trace_method_name |
| The full path of the AML method that the user wants to trace. |
| Note that the full path shouldn't contain the trailing "_"s in its |
| name segments but may contain "\" to form an absolute path. |
| |
| trace_debug_layer |
| The temporary debug_layer used when the tracing feature is enabled. |
| Using ACPI_EXECUTER (0x80) by default, which is the debug_layer |
| used to match all "AML tracer" logs. |
| |
| trace_debug_level |
| The temporary debug_level used when the tracing feature is enabled. |
| Using ACPI_LV_TRACE_POINT (0x10) by default, which is the |
| debug_level used to match all "AML tracer" logs. |
| |
| trace_state |
| The status of the tracing feature. |
| Users can enable/disable this debug tracing feature by executing |
| the following command: |
| # echo string > /sys/module/acpi/parameters/trace_state |
| Where "string" should be one of the followings: |
| "disable" |
| Disable the method tracing feature. |
| "enable" |
| Enable the method tracing feature. |
| ACPICA debugging messages matching |
| "trace_debug_layer/trace_debug_level" during any method |
| execution will be logged. |
| "method" |
| Enable the method tracing feature. |
| ACPICA debugging messages matching |
| "trace_debug_layer/trace_debug_level" during method execution |
| of "trace_method_name" will be logged. |
| "method-once" |
| Enable the method tracing feature. |
| ACPICA debugging messages matching |
| "trace_debug_layer/trace_debug_level" during method execution |
| of "trace_method_name" will be logged only once. |
| "opcode" |
| Enable the method tracing feature. |
| ACPICA debugging messages matching |
| "trace_debug_layer/trace_debug_level" during method/opcode |
| execution of "trace_method_name" will be logged. |
| "opcode-once" |
| Enable the method tracing feature. |
| ACPICA debugging messages matching |
| "trace_debug_layer/trace_debug_level" during method/opcode |
| execution of "trace_method_name" will be logged only once. |
| Note that, the difference between the "enable" and other feature |
| enabling options are: |
| 1. When "enable" is specified, since |
| "trace_debug_layer/trace_debug_level" shall apply to all control |
| method evaluations, after configuring "trace_state" to "enable", |
| "trace_method_name" will be reset to NULL. |
| 2. When "method/opcode" is specified, if |
| "trace_method_name" is NULL when "trace_state" is configured to |
| these options, the "trace_debug_layer/trace_debug_level" will |
| apply to all control method evaluations. |
