When the nominal_freq recorded by the kernel is equal to lowest_freq and
the frequency reduction operation is triggered externally, there is a
conversion logic error in cppc_perf_to_khz(), causing the kernel to be
unable to feedback the true frequency.
Fix this by adding the branch processing logic when nominal_freq is equal
to lowest_freq.
Fixes: ec1c7ad47664 ("cpufreq: CPPC: Fix performance/frequency conversion")
Signed-off-by: liwei <liwei728@xxxxxxxxxx>
---
drivers/acpi/cppc_acpi.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index a40b6f3946ef..92aac6974e0e 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1869,9 +1869,15 @@ unsigned int cppc_perf_to_khz(struct cppc_perf_caps *caps, unsigned int perf)
u64 mul, div;
if (caps->lowest_freq && caps->nominal_freq) {
- mul = caps->nominal_freq - caps->lowest_freq;
+ /* Avoid the 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;
+ div = caps->nominal_perf - caps->lowest_perf;
+ }
mul *= KHZ_PER_MHZ;
- div = caps->nominal_perf - caps->lowest_perf;
offset = caps->nominal_freq * KHZ_PER_MHZ -
div64_u64(caps->nominal_perf * mul, div);
} else {
--
2.25.1
