2024-05-06 08:05:09

by liwei (JK)

Subject: [PATCH v2] cpufreq/cppc: fix perf_to_khz/khz_to_perf conversion exception

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 the branch processing logic when nominal_freq is equal
to lowest_freq.

Fixes: ec1c7ad47664 ("cpufreq: CPPC: Fix performance/frequency conversion")
Signed-off-by: liwei <[email protected]>
---
v2:
- Fix similar issue in cppc_khz_to_perf()

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 a40b6f3946ef..e3a0d6b46b24 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 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 {
@@ -1892,11 +1898,17 @@ 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
--
2.25.1

2024-05-20 07:25:32

by Viresh Kumar

Subject: Re: [PATCH v2] cpufreq/cppc: fix perf_to_khz/khz_to_perf conversion exception

On 06-05-24, 15:58, liwei wrote:
> 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 the branch processing logic when nominal_freq is equal
> to lowest_freq.
>
> Fixes: ec1c7ad47664 ("cpufreq: CPPC: Fix performance/frequency conversion")
> Signed-off-by: liwei <[email protected]>
> ---
> v2:
> - Fix similar issue in cppc_khz_to_perf()
>
> drivers/acpi/cppc_acpi.c | 22 +++++++++++++++++-----
> 1 file changed, 17 insertions(+), 5 deletions(-)

Acked-by: Viresh Kumar <[email protected]>

--
viresh