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

[Sumit Gupta]

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