June 2017
Intermediate to advanced
478 pages
13h 14m
English
Content preview from Mastering Embedded Linux Programming - Second Edition
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The CPUFreq driver
Linux has a component named CPUFreq that manages the transitions between OPPs. It is part of the board support for the package for each SoC. CPUFreq consists of drivers in drivers/cpufreq/, which make the transition from one OPP to another, and a set of governors that implement the policy of when to switch. It is controlled per-CPU via the /sys/devices/system/cpu/cpuN/cpufreq directory, with N being the CPU number. In there, we find a number of files, the most interesting of which are as follows:
- cpuinfo_cur_freq, cpuinfo_max_freq and cpuinfo_min_freq: The current frequency for this CPU, together with the maximum and minimum, measured in KHz.
- cpuinfo_transition_latency: The time, in nanoseconds, to switch from one OPP ...
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