diff options
Diffstat (limited to 'Documentation/acpi')
| -rw-r--r-- | Documentation/acpi/cppc_sysfs.txt | 69 | ||||
| -rw-r--r-- | Documentation/acpi/method-customizing.txt | 10 |
2 files changed, 74 insertions, 5 deletions
diff --git a/Documentation/acpi/cppc_sysfs.txt b/Documentation/acpi/cppc_sysfs.txt new file mode 100644 index 000000000000..f20fb445135d --- /dev/null +++ b/Documentation/acpi/cppc_sysfs.txt @@ -0,0 +1,69 @@ + + Collaborative Processor Performance Control (CPPC) + +CPPC defined in the ACPI spec describes a mechanism for the OS to manage the +performance of a logical processor on a contigious and abstract performance +scale. CPPC exposes a set of registers to describe abstract performance scale, +to request performance levels and to measure per-cpu delivered performance. + +For more details on CPPC please refer to the ACPI specification at: + +http://uefi.org/specifications + +Some of the CPPC registers are exposed via sysfs under: + +/sys/devices/system/cpu/cpuX/acpi_cppc/ + +for each cpu X + +-------------------------------------------------------------------------------- + +$ ls -lR /sys/devices/system/cpu/cpu0/acpi_cppc/ +/sys/devices/system/cpu/cpu0/acpi_cppc/: +total 0 +-r--r--r-- 1 root root 65536 Mar 5 19:38 feedback_ctrs +-r--r--r-- 1 root root 65536 Mar 5 19:38 highest_perf +-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_freq +-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_nonlinear_perf +-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_perf +-r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_freq +-r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_perf +-r--r--r-- 1 root root 65536 Mar 5 19:38 reference_perf +-r--r--r-- 1 root root 65536 Mar 5 19:38 wraparound_time + +-------------------------------------------------------------------------------- + +* highest_perf : Highest performance of this processor (abstract scale). +* nominal_perf : Highest sustained performance of this processor (abstract scale). +* lowest_nonlinear_perf : Lowest performance of this processor with nonlinear + power savings (abstract scale). +* lowest_perf : Lowest performance of this processor (abstract scale). + +* lowest_freq : CPU frequency corresponding to lowest_perf (in MHz). +* nominal_freq : CPU frequency corresponding to nominal_perf (in MHz). + The above frequencies should only be used to report processor performance in + freqency instead of abstract scale. These values should not be used for any + functional decisions. + +* feedback_ctrs : Includes both Reference and delivered performance counter. + Reference counter ticks up proportional to processor's reference performance. + Delivered counter ticks up proportional to processor's delivered performance. +* wraparound_time: Minimum time for the feedback counters to wraparound (seconds). +* reference_perf : Performance level at which reference performance counter + accumulates (abstract scale). + +-------------------------------------------------------------------------------- + + Computing Average Delivered Performance + +Below describes the steps to compute the average performance delivered by taking +two different snapshots of feedback counters at time T1 and T2. + +T1: Read feedback_ctrs as fbc_t1 + Wait or run some workload +T2: Read feedback_ctrs as fbc_t2 + +delivered_counter_delta = fbc_t2[del] - fbc_t1[del] +reference_counter_delta = fbc_t2[ref] - fbc_t1[ref] + +delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta diff --git a/Documentation/acpi/method-customizing.txt b/Documentation/acpi/method-customizing.txt index a3f598e141f2..7235da975f23 100644 --- a/Documentation/acpi/method-customizing.txt +++ b/Documentation/acpi/method-customizing.txt @@ -16,7 +16,8 @@ control method rather than override the entire DSDT, because kernel rebuild/reboot is not needed and test result can be got in minutes. Note: Only ACPI METHOD can be overridden, any other object types like - "Device", "OperationRegion", are not recognized. + "Device", "OperationRegion", are not recognized. Methods + declared inside scope operators are also not supported. Note: The same ACPI control method can be overridden for many times, and it's always the latest one that used by Linux/kernel. Note: To get the ACPI debug object output (Store (AAAA, Debug)), @@ -32,8 +33,6 @@ Note: To get the ACPI debug object output (Store (AAAA, Debug)), DefinitionBlock ("", "SSDT", 1, "", "", 0x20080715) { - External (ACON) - Method (\_SB_.AC._PSR, 0, NotSerialized) { Store ("In AC _PSR", Debug) @@ -42,9 +41,10 @@ Note: To get the ACPI debug object output (Store (AAAA, Debug)), } Note that the full pathname of the method in ACPI namespace should be used. - And remember to use "External" to declare external objects. e) assemble the file to generate the AML code of the method. - e.g. "iasl psr.asl" (psr.aml is generated as a result) + e.g. "iasl -vw 6084 psr.asl" (psr.aml is generated as a result) + If parameter "-vw 6084" is not supported by your iASL compiler, + please try a newer version. f) mount debugfs by "mount -t debugfs none /sys/kernel/debug" g) override the old method via the debugfs by running "cat /tmp/psr.aml > /sys/kernel/debug/acpi/custom_method" |