On Thu, Oct 24, 2024 at 4:16 AM liwei <liwei728@xxxxxxxxxx> 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 <liwei728@xxxxxxxxxx>
> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> v2:
> - Fix similar issue in cppc_khz_to_perf()
> ---
> v3:
> - Add acked-by tag
> ---
> 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 b73b3aa92f3f..c3fc2c05d868 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -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) {
> - 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 {
> @@ -1939,11 +1945,17 @@ 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
> --
Applied as 6.12-rc material, thanks!
