Commit d93df29b authored by liwei's avatar liwei Committed by Rafael J. Wysocki
Browse files

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 a branch processing logic when nominal_freq is equal
to lowest_freq.

Fixes: ec1c7ad4 ("cpufreq: CPPC: Fix performance/frequency conversion")
Signed-off-by: default avatarliwei <liwei728@huawei.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20241024022952.2627694-1-liwei728@huawei.com


[ rjw: Subject and changelog edits ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 29dcbea9

drivers/acpi/cppc_acpi.c

+17 −5
Original line number Diff line number Diff line
@@ -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