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When CPPC is being used by ACPI on arm64, user space tools such as
cpupower report CPU frequency values from sysfs that are incorrect.
What the driver was doing was reporting the values given by ACPI tables
in whatever scale was used to provide them. However, the ACPI spec
defines the CPPC values as unitless abstract numbers. Internal kernel
structures such as struct perf_cap, in contrast, expect these values
to be in KHz. When these struct values get reported via sysfs, the
user space tools also assume they are in KHz, causing them to report
incorrect values (for example, reporting a CPU frequency of 1MHz when
it should be 1.8GHz).
The downside is that this approach has some assumptions:
(1) It relies on SMBIOS3 being used, *and* that the Max Frequency
value for a processor is set to a non-zero value.
(2) It assumes that all processors run at the same speed, or that
the CPPC values have all been scaled to reflect relative speed.
This patch retrieves the largest CPU Max Frequency from a type 4 DMI
record that it can find. This may not be an issue, however, as a
sampling of DMI data on x86 and arm64 indicates there is often only
one such record regardless. Since CPPC is relatively new, it is
unclear if the ACPI ASL will always be written to reflect any sort
of relative performance of processors of differing speeds.
(3) It assumes that performance and frequency both scale linearly.
For arm64 servers, this may be sufficient, but it does rely on
firmware values being set correctly. Hence, other approaches will
be considered in the future.
This has been tested on three arm64 servers, with and without DMI, with
and without CPPC support.
Signed-off-by: Al Stone <ahs3@redhat.com>
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Since struct cpudata is defined in a header file, add prefix cppc_ to
make it not a generic name. Otherwise it causes compile issue in locally
define structure with the same name.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Compute the expected transition latency for frequency transitions
using the values from the PCCT tables when the desired perf
register is in PCC.
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Reviewed-by: Alexey Klimov <alexey.klimov@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Add a function to cleanup at module exit and export
appropriate GPL string to enable moduler support
for the cppc_cpufreq driver.
Reported-by: Srinivas Pandruvada <srinivas.pandruvada@intel.com>
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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The CPU policy struct indicates the co-ordination type
for all CPUs of a common freq domain. Initialize it
correctly using the CPU specific data gathered from
CPPC ACPI lib via acpi_get_psd_map().
The PSD object is optional, so the cpu->shared_type
can also be 0. So instead of assuming any value other
than SW_ANY(0xFD) is unsupported, explictly check
if shared_type is SW_ALL and then bail.
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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The kfree() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.
This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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This driver utilizes the methods introduced in a previous
patch titled - "ACPI: Introduce CPU performance controls using CPPC"
and enables usage with existing CPUFreq governors.
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Reviewed-by: Al Stone <al.stone@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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