Commit c579f91a authored by liwei's avatar liwei
Browse files

cpufreq/cppc: fix perf_to_khz/khz_to_perf conversion 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I99VPY


CVE: NA

--------------------------------

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: ec1c7ad4 ("cpufreq: CPPC: Fix performance/frequency conversion")
Signed-off-by: default avatarliwei <liwei728@huawei.com>
parent 0982dad0

drivers/cpufreq/cppc_cpufreq.c

+17 −5
Original line number Diff line number Diff line
@@ -98,7 +98,7 @@ static u64 cppc_get_dmi_max_khz(void) 
 * use them to convert perf to freq and vice versa. The conversion is

 * extrapolated as an affine function passing by the 2 points:

 *  - (Low perf, Low freq)

 *  - (Nominal perf, Nominal perf)

 *  - (Nominal perf, Nominal freq)

 */

static unsigned int cppc_cpufreq_perf_to_khz(struct cppc_cpudata *cpu_data,

					unsigned int perf)
@@ -109,8 +109,14 @@ static unsigned int cppc_cpufreq_perf_to_khz(struct cppc_cpudata *cpu_data, 
	u64 mul, div;



	if (caps->lowest_freq && caps->nominal_freq) {

		/* Avoid the special case when nominal_freq is equal to lowest_freq */

		if (caps->nominal_freq == caps->lowest_freq) {

			mul = caps->nominal_freq;

			div = caps->nominal_perf;

		} else {

			mul = caps->nominal_freq - caps->lowest_freq;

			div = caps->nominal_perf - caps->lowest_perf;

		}

		offset = caps->nominal_freq - div64_u64(caps->nominal_perf * mul, div);

	} else {

		if (!max_khz)
@@ -134,8 +140,14 @@ static unsigned int cppc_cpufreq_khz_to_perf(struct cppc_cpudata *cpu_data, 
	u64  mul, div;



	if (caps->lowest_freq && caps->nominal_freq) {

		/* Avoid special case when nominal_freq is equal to lowest_freq */

		if (caps->nominal_freq == caps->lowest_freq) {

			mul = caps->nominal_perf;

			div = caps->nominal_freq;

		} else {

			mul = caps->nominal_perf - caps->lowest_perf;

			div = caps->nominal_freq - caps->lowest_freq;

		}

		offset = caps->nominal_perf - div64_u64(caps->nominal_freq * mul, div);

	} else {

		if (!max_khz)