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cpufreq: CPPC: fix perf_to_khz/khz_to_perf conversion exception

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When the nominal_freq recorded by the kernel is equal to the lowest_freq,
and the frequency adjustment operation is triggered externally, there is
a logic error in cppc_perf_to_khz()/cppc_khz_to_perf(), resulting in perf
and khz conversion errors.

Fix this by adding a branch processing logic when nominal_freq is equal
to lowest_freq.

Fixes: ec1c7ad476 ("cpufreq: CPPC: Fix performance/frequency conversion")
Signed-off-by: liwei <liwei728@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20241024022952.2627694-1-liwei728@huawei.com
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
liwei 2024-10-24 10:29:52 +08:00 committed by Rafael J. Wysocki
parent 29dcbea924
commit d93df29bda
1 changed files with 17 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

14
drivers/acpi/cppc_acpi.c
View file

@ -1916,9 +1916,15 @@ unsigned int cppc_perf_to_khz(struct cppc_perf_caps *caps, unsigned int perf)
u64 mul, div;
if (caps->lowest_freq && caps->nominal_freq) {
/* Avoid special case when nominal_freq is equal to lowest_freq */
if (caps->lowest_freq == caps->nominal_freq) {
mul = caps->nominal_freq;
div = caps->nominal_perf;
} else {
mul = caps->nominal_freq - caps->lowest_freq;
mul *= KHZ_PER_MHZ;
div = caps->nominal_perf - caps->lowest_perf;
}
mul *= KHZ_PER_MHZ;
offset = caps->nominal_freq * KHZ_PER_MHZ -
div64_u64(caps->nominal_perf * mul, div);
} else {
@ -1942,8 +1948,14 @@ unsigned int cppc_khz_to_perf(struct cppc_perf_caps *caps, unsigned int freq)
u64 mul, div;
if (caps->lowest_freq && caps->nominal_freq) {
/* Avoid special case when nominal_freq is equal to lowest_freq */
if (caps->lowest_freq == caps->nominal_freq) {
mul = caps->nominal_perf;
div = caps->nominal_freq;
} else {
mul = caps->nominal_perf - caps->lowest_perf;
div = caps->nominal_freq - caps->lowest_freq;
}
/*
* We don't need to convert to kHz for computing offset and can
* directly use nominal_freq and lowest_freq as the div64_u64