[Patch 2/2] ACPI: processor: Add support to configure CPUFREQ reduction pctg

From: Sumit Gupta
Date: Thu Aug 17 2023 - 05:31:49 EST


From: Srikar Srimath Tirumala <srikars@xxxxxxxxxx>

Add support to configure the CPUFREQ reduction percentage and set the
maximum number of throttling steps accordingly. Current implementation
of processor_thermal performs software throttling in fixed steps of
"20%" which can be too coarse for some platforms. Change that by adding
new config to provide the reduction percentage.

Signed-off-by: Srikar Srimath Tirumala <srikars@xxxxxxxxxx>
Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
---
drivers/acpi/Kconfig | 15 +++++++++++++++
drivers/acpi/processor_thermal.c | 19 ++++++++++++++++---
2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 00dd309b6682..287cf58defbf 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -254,6 +254,21 @@ config ACPI_DOCK
config ACPI_CPU_FREQ_PSS
bool

+config ACPI_CPU_FREQ_THERM_HAS_PARAMS
+ bool "CPU frequency throttling control"
+ depends on ACPI_PROCESSOR
+
+config ACPI_CPU_FREQ_THERM_MIN_THROT_PCTG
+ int "Minimum throttle percentage for processor_thermal cooling device"
+ depends on ACPI_CPU_FREQ_THERM_HAS_PARAMS
+ default 20
+ help
+ The processor_thermal driver uses this config to calculate the
+ percentage amount by which cpu frequency must be reduced for each
+ cooling state. The config is also used to calculate the maximum number
+ of throttling steps or cooling states supported by the driver. Value
+ must be an unsigned integer in the range [1, 50].
+
config ACPI_PROCESSOR_CSTATE
def_bool y
depends on ACPI_PROCESSOR
diff --git a/drivers/acpi/processor_thermal.c b/drivers/acpi/processor_thermal.c
index b7c6287eccca..ee443cc69b73 100644
--- a/drivers/acpi/processor_thermal.c
+++ b/drivers/acpi/processor_thermal.c
@@ -25,8 +25,20 @@
* _any_ cpufreq driver and not only the acpi-cpufreq driver.
*/

-#define CPUFREQ_THERMAL_MIN_STEP 0
-#define CPUFREQ_THERMAL_MAX_STEP 3
+#define CPUFREQ_THERMAL_MIN_STEP 0
+#ifdef CONFIG_ACPI_CPU_FREQ_THERM_HAS_PARAMS
+#define CPUFREQ_THERMAL_PCTG CONFIG_ACPI_CPU_FREQ_THERM_MIN_THROT_PCTG
+
+/* Derive the MAX_STEP from minimum throttle percentage so that the reduction
+ * percentage does end up becoming negative. Also cap the MAX_STEP so that
+ * the CPU performance doesn't become 0.
+ */
+#define CPUFREQ_THERMAL_MAX_STEP ((100 / CPUFREQ_THERMAL_PCTG) - 1)
+
+#else
+#define CPUFREQ_THERMAL_MAX_STEP 3
+#define CPUFREQ_THERMAL_PCTG 20
+#endif

static DEFINE_PER_CPU(unsigned int, cpufreq_thermal_reduction_pctg);

@@ -113,7 +125,8 @@ static int cpufreq_set_cur_state(unsigned int cpu, int state)
if (!policy)
return -EINVAL;

- max_freq = (policy->cpuinfo.max_freq * (100 - reduction_pctg(i) * 20)) / 100;
+ max_freq = (policy->cpuinfo.max_freq *
+ (100 - reduction_pctg(i) * CPUFREQ_THERMAL_PCTG)) / 100;

cpufreq_cpu_put(policy);

--
2.17.1