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Diffstat (limited to 'Documentation/cpu-freq/user-guide.txt')
| -rw-r--r-- | Documentation/cpu-freq/user-guide.txt | 73 |
1 files changed, 47 insertions, 26 deletions
diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt index 6c442d8426b..ff2f28332cc 100644 --- a/Documentation/cpu-freq/user-guide.txt +++ b/Documentation/cpu-freq/user-guide.txt @@ -23,6 +23,7 @@ Contents: 1.3 sparc64 1.4 ppc 1.5 SuperH +1.6 Blackfin 2. "Policy" / "Governor"? 2.1 Policy @@ -30,7 +31,6 @@ Contents: 3. How to change the CPU cpufreq policy and/or speed 3.1 Preferred interface: sysfs -3.2 Deprecated interfaces @@ -92,10 +92,19 @@ Several "PowerBook" and "iBook2" notebooks are supported. 1.5 SuperH ---------- -The following SuperH processors are supported by cpufreq: +All SuperH processors supporting rate rounding through the clock +framework are supported by cpufreq. -SH-3 -SH-4 +1.6 Blackfin +------------ + +The following Blackfin processors are supported by cpufreq: + +BF522, BF523, BF524, BF525, BF526, BF527, Rev 0.1 or higher +BF531, BF532, BF533, Rev 0.3 or higher +BF534, BF536, BF537, Rev 0.2 or higher +BF561, Rev 0.3 or higher +BF542, BF544, BF547, BF548, BF549, Rev 0.1 or higher 2. "Policy" / "Governor" ? @@ -142,6 +151,18 @@ cpuinfo_min_freq : this file shows the minimum operating frequency the processor can run at(in kHz) cpuinfo_max_freq : this file shows the maximum operating frequency the processor can run at(in kHz) +cpuinfo_transition_latency The time it takes on this CPU to + switch between two frequencies in nano + seconds. If unknown or known to be + that high that the driver does not + work with the ondemand governor, -1 + (CPUFREQ_ETERNAL) will be returned. + Using this information can be useful + to choose an appropriate polling + frequency for a kernel governor or + userspace daemon. Make sure to not + switch the frequency too often + resulting in performance loss. scaling_driver : this file shows what cpufreq driver is used to set the frequency on this CPU @@ -155,7 +176,9 @@ scaling_governor, and by "echoing" the name of another work on some specific architectures or processors. -cpuinfo_cur_freq : Current speed of the CPU, in KHz. +cpuinfo_cur_freq : Current frequency of the CPU as obtained from + the hardware, in KHz. This is the frequency + the CPU actually runs at. scaling_available_frequencies : List of available frequencies, in KHz. @@ -167,15 +190,29 @@ scaling_max_freq show the current "policy limits" (in first set scaling_max_freq, then scaling_min_freq. -affected_cpus : List of CPUs that require software coordination - of frequency. +affected_cpus : List of Online CPUs that require software + coordination of frequency. -related_cpus : List of CPUs that need some sort of frequency - coordination, whether software or hardware. +related_cpus : List of Online + Offline CPUs that need software + coordination of frequency. scaling_driver : Hardware driver for cpufreq. -scaling_cur_freq : Current frequency of the CPU, in KHz. +scaling_cur_freq : Current frequency of the CPU as determined by + the governor and cpufreq core, in KHz. This is + the frequency the kernel thinks the CPU runs + at. + +bios_limit : If the BIOS tells the OS to limit a CPU to + lower frequencies, the user can read out the + maximum available frequency from this file. + This typically can happen through (often not + intended) BIOS settings, restrictions + triggered through a service processor or other + BIOS/HW based implementations. + This does not cover thermal ACPI limitations + which can be detected through the generic + thermal driver. If you have selected the "userspace" governor which allows you to set the CPU operating frequency to a specific value, you can read out @@ -185,19 +222,3 @@ scaling_setspeed. By "echoing" a new frequency into this you can change the speed of the CPU, but only within the limits of scaling_min_freq and scaling_max_freq. - - -3.2 Deprecated Interfaces -------------------------- - -Depending on your kernel configuration, you might find the following -cpufreq-related files: -/proc/cpufreq -/proc/sys/cpu/*/speed -/proc/sys/cpu/*/speed-min -/proc/sys/cpu/*/speed-max - -These are files for deprecated interfaces to cpufreq, which offer far -less functionality. Because of this, these interfaces aren't described -here. - |