6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: liwei <liwei728@xxxxxxxxxx>
[ Upstream commit d93df29bdab133b85e94b3c328e7fe26a0ebd56c ]
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: ec1c7ad47664 ("cpufreq: CPPC: Fix performance/frequency conversion")
Signed-off-by: liwei <liwei728@xxxxxxxxxx>
Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Link: https://patch.msgid.link/20241024022952.2627694-1-liwei728@xxxxxxxxxx
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/acpi/cppc_acpi.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 2297404fe4714..5df417626fd10 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1912,9 +1912,15 @@ 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 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 {
@@ -1935,11 +1941,17 @@ unsigned int cppc_khz_to_perf(struct cppc_perf_caps *caps, unsigned int freq)
{
s64 retval, offset = 0;
static u64 max_khz;
- u64 mul, div;
+ u64 mul, div;
if (caps->lowest_freq && caps->nominal_freq) {
- mul = caps->nominal_perf - caps->lowest_perf;
- div = caps->nominal_freq - caps->lowest_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
--
2.43.0
