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The code in powernv-cpufreq, makes the following two assumptions which
are not guaranteed by the device-tree bindings:
1) Pstate ids are continguous: This is used in pstate_to_idx() to
obtain the reverse map from a pstate to it's corresponding
entry into the cpufreq frequency table.
2) Every Pstate should always lie between the max and the min
pstates that are explicitly reported in the device tree: This
is used to determine whether a pstate reported by the PMSR is
out of bounds.
Both these assumptions are unwarranted and can change on future
platforms.
In this patch, we maintain the reverse map from a pstate to it's index
in the cpufreq frequency table and use this in pstate_to_idx(). This
does away with the assumptions (1) mentioned above, and will work with
non continguous pstate ids. If no entry exists for a particular
pstate, then such a pstate is treated as being out of bounds. This
gets rid of assumption (2).
On all the existing platforms, where the pstates are 8-bit long
values, the new implementation of pstate_to_idx() takes constant time.
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.