cpufreq / CPPC: Support for CPPC v3

Use CPPC v3 entries to convert the abstract processor performance to
processor frequency in KHz.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cppc_cpufreq.c

@@ -42,9 +42,6 @@
  */
 static struct cppc_cpudata **all_cpu_data;
 
-/* Capture the max KHz from DMI */
-static u64 cppc_dmi_max_khz;
-
 /* Callback function used to retrieve the max frequency from DMI */
 static void cppc_find_dmi_mhz(const struct dmi_header *dm, void *private)
 {
@@ -75,6 +72,64 @@ static u64 cppc_get_dmi_max_khz(void)
 	return (1000 * mhz);
 }
 
+/*
+ * If CPPC lowest_freq and nominal_freq registers are exposed then we can
+ * use them to convert perf to freq and vice versa
+ *
+ * If the perf/freq point lies between Nominal and Lowest, we can treat
+ * (Low perf, Low freq) and (Nom Perf, Nom freq) as 2D co-ordinates of a line
+ * and extrapolate the rest
+ * For perf/freq > Nominal, we use the ratio perf:freq at Nominal for conversion
+ */
+static unsigned int cppc_cpufreq_perf_to_khz(struct cppc_cpudata *cpu,
+					unsigned int perf)
+{
+	static u64 max_khz;
+	struct cppc_perf_caps *caps = &cpu->perf_caps;
+	u64 mul, div;
+
+	if (caps->lowest_freq && caps->nominal_freq) {
+		if (perf >= caps->nominal_perf) {
+			mul = caps->nominal_freq;
+			div = caps->nominal_perf;
+		} else {
+			mul = caps->nominal_freq - caps->lowest_freq;
+			div = caps->nominal_perf - caps->lowest_perf;
+		}
+	} else {
+		if (!max_khz)
+			max_khz = cppc_get_dmi_max_khz();
+		mul = max_khz;
+		div = cpu->perf_caps.highest_perf;
+	}
+	return (u64)perf * mul / div;
+}
+
+static unsigned int cppc_cpufreq_khz_to_perf(struct cppc_cpudata *cpu,
+					unsigned int freq)
+{
+	static u64 max_khz;
+	struct cppc_perf_caps *caps = &cpu->perf_caps;
+	u64  mul, div;
+
+	if (caps->lowest_freq && caps->nominal_freq) {
+		if (freq >= caps->nominal_freq) {
+			mul = caps->nominal_perf;
+			div = caps->nominal_freq;
+		} else {
+			mul = caps->lowest_perf;
+			div = caps->lowest_freq;
+		}
+	} else {
+		if (!max_khz)
+			max_khz = cppc_get_dmi_max_khz();
+		mul = cpu->perf_caps.highest_perf;
+		div = max_khz;
+	}
+
+	return (u64)freq * mul / div;
+}
+
 static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
 		unsigned int target_freq,
 		unsigned int relation)
@@ -86,7 +141,7 @@ static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
 
 	cpu = all_cpu_data[policy->cpu];
 
-	desired_perf = (u64)target_freq * cpu->perf_caps.highest_perf / cppc_dmi_max_khz;
+	desired_perf = cppc_cpufreq_khz_to_perf(cpu, target_freq);
 	/* Return if it is exactly the same perf */
 	if (desired_perf == cpu->perf_ctrls.desired_perf)
 		return ret;
@@ -143,24 +198,24 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
 		return ret;
 	}
 
-	cppc_dmi_max_khz = cppc_get_dmi_max_khz();
+	/* Convert the lowest and nominal freq from MHz to KHz */
+	cpu->perf_caps.lowest_freq *= 1000;
+	cpu->perf_caps.nominal_freq *= 1000;
 
 	/*
 	 * Set min to lowest nonlinear perf to avoid any efficiency penalty (see
 	 * Section 8.4.7.1.1.5 of ACPI 6.1 spec)
 	 */
-	policy->min = cpu->perf_caps.lowest_nonlinear_perf * cppc_dmi_max_khz /
-		cpu->perf_caps.highest_perf;
-	policy->max = cppc_dmi_max_khz;
+	policy->min = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.lowest_nonlinear_perf);
+	policy->max = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.highest_perf);
 
 	/*
 	 * Set cpuinfo.min_freq to Lowest to make the full range of performance
 	 * available if userspace wants to use any perf between lowest & lowest
 	 * nonlinear perf
 	 */
-	policy->cpuinfo.min_freq = cpu->perf_caps.lowest_perf * cppc_dmi_max_khz /
-		cpu->perf_caps.highest_perf;
-	policy->cpuinfo.max_freq = cppc_dmi_max_khz;
+	policy->cpuinfo.min_freq = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.lowest_perf);
+	policy->cpuinfo.max_freq = cppc_cpufreq_perf_to_khz(cpu, cpu->perf_caps.highest_perf);
 
 	policy->transition_delay_us = cppc_get_transition_latency(cpu_num) /
 		NSEC_PER_USEC;
@@ -187,7 +242,8 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	cpu->cur_policy = policy;
 
 	/* Set policy->cur to max now. The governors will adjust later. */
-	policy->cur = cppc_dmi_max_khz;
+	policy->cur = cppc_cpufreq_perf_to_khz(cpu,
+					cpu->perf_caps.highest_perf);
 	cpu->perf_ctrls.desired_perf = cpu->perf_caps.highest_perf;
 
 	ret = cppc_set_perf(cpu_num, &cpu->perf_ctrls);