Message-ID: <20260120145623.2959636-7-sumitg@nvidia.com>
Date: Tue, 20 Jan 2026 20:26:20 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: <rafael@...nel.org>, <viresh.kumar@...aro.org>, <pierre.gondois@....com>,
	<zhenglifeng1@...wei.com>, <ionela.voinescu@....com>, <lenb@...nel.org>,
	<robert.moore@...el.com>, <corbet@....net>, <rdunlap@...radead.org>,
	<ray.huang@....com>, <gautham.shenoy@....com>, <mario.limonciello@....com>,
	<perry.yuan@....com>, <zhanjie9@...ilicon.com>, <linux-pm@...r.kernel.org>,
	<linux-acpi@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<acpica-devel@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
CC: <linux-tegra@...r.kernel.org>, <treding@...dia.com>,
	<jonathanh@...dia.com>, <vsethi@...dia.com>, <ksitaraman@...dia.com>,
	<sanjayc@...dia.com>, <nhartman@...dia.com>, <bbasu@...dia.com>,
	<sumitg@...dia.com>
Subject: [PATCH v6 6/9] ACPI: CPPC: add APIs and sysfs interface for min/max_perf

Add cppc_get/set_min_perf() and cppc_get/set_max_perf() APIs to read and
write the MIN_PERF and MAX_PERF registers.

Also add sysfs interfaces (min_perf, max_perf) in cppc_cpufreq driver
to expose these controls to userspace. The sysfs values are in frequency
(kHz) for consistency with other cpufreq sysfs files.

A mutex is used to serialize sysfs store operations to ensure hardware
register writes and perf_ctrls updates are atomic.

Signed-off-by: Sumit Gupta <sumitg@...dia.com>
---
 drivers/acpi/cppc_acpi.c       |  44 +++++++++
 drivers/cpufreq/cppc_cpufreq.c | 157 +++++++++++++++++++++++++++++++++
 include/acpi/cppc_acpi.h       |  20 +++++
 3 files changed, 221 insertions(+)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 45c6bd6ec24b..46bf45f8b0f3 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1743,6 +1743,50 @@ int cppc_set_auto_sel(int cpu, bool enable)
 }
 EXPORT_SYMBOL_GPL(cppc_set_auto_sel);
 
+/**
+ * cppc_get_min_perf - Read minimum performance register.
+ * @cpu: CPU from which to read register.
+ * @min_perf: Return address.
+ */
+int cppc_get_min_perf(int cpu, u64 *min_perf)
+{
+	return cppc_get_reg_val(cpu, MIN_PERF, min_perf);
+}
+EXPORT_SYMBOL_GPL(cppc_get_min_perf);
+
+/**
+ * cppc_set_min_perf - Write minimum performance register.
+ * @cpu: CPU to which to write register.
+ * @min_perf: the desired minimum performance value to be updated.
+ */
+int cppc_set_min_perf(int cpu, u32 min_perf)
+{
+	return cppc_set_reg_val(cpu, MIN_PERF, min_perf);
+}
+EXPORT_SYMBOL_GPL(cppc_set_min_perf);
+
+/**
+ * cppc_get_max_perf - Read maximum performance register.
+ * @cpu: CPU from which to read register.
+ * @max_perf: Return address.
+ */
+int cppc_get_max_perf(int cpu, u64 *max_perf)
+{
+	return cppc_get_reg_val(cpu, MAX_PERF, max_perf);
+}
+EXPORT_SYMBOL_GPL(cppc_get_max_perf);
+
+/**
+ * cppc_set_max_perf - Write maximum performance register.
+ * @cpu: CPU to which to write register.
+ * @max_perf: the desired maximum performance value to be updated.
+ */
+int cppc_set_max_perf(int cpu, u32 max_perf)
+{
+	return cppc_set_reg_val(cpu, MAX_PERF, max_perf);
+}
+EXPORT_SYMBOL_GPL(cppc_set_max_perf);
+
 /**
  * cppc_set_enable - Set to enable CPPC on the processor by writing the
  * Continuous Performance Control package EnableRegister field.
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 229880c4eedb..66e183b45fb0 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -28,6 +28,8 @@
 
 static struct cpufreq_driver cppc_cpufreq_driver;
 
+static DEFINE_MUTEX(cppc_cpufreq_autonomous_lock);
+
 #ifdef CONFIG_ACPI_CPPC_CPUFREQ_FIE
 static enum {
 	FIE_UNSET = -1,
@@ -570,6 +572,35 @@ static void populate_efficiency_class(void)
 }
 #endif
 
+/* Set min/max performance HW register and cache the value */
+static int cppc_cpufreq_set_mperf_reg(struct cpufreq_policy *policy,
+				      u64 val, bool is_min)
+{
+	struct cppc_cpudata *cpu_data = policy->driver_data;
+	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
+	unsigned int cpu = policy->cpu;
+	u32 perf;
+	int ret;
+
+	perf = clamp(val, caps->lowest_perf, caps->highest_perf);
+
+	ret = is_min ? cppc_set_min_perf(cpu, perf) :
+		       cppc_set_max_perf(cpu, perf);
+	if (ret) {
+		if (ret != -EOPNOTSUPP)
+			pr_warn("CPU%d: set %s_perf=%u failed (%d)\n",
+				cpu, is_min ? "min" : "max", perf, ret);
+		return ret;
+	}
+
+	if (is_min)
+		cpu_data->perf_ctrls.min_perf = perf;
+	else
+		cpu_data->perf_ctrls.max_perf = perf;
+
+	return 0;
+}
+
 static struct cppc_cpudata *cppc_cpufreq_get_cpu_data(unsigned int cpu)
 {
 	struct cppc_cpudata *cpu_data;
@@ -918,16 +949,142 @@ CPPC_CPUFREQ_ATTR_RW_U64(auto_act_window, cppc_get_auto_act_window,
 CPPC_CPUFREQ_ATTR_RW_U64(energy_performance_preference_val,
 			 cppc_get_epp_perf, cppc_set_epp)
 
+/**
+ * show_min_perf - Show minimum performance as frequency (kHz)
+ * @policy: cpufreq policy
+ * @buf: buffer to write the frequency value to
+ *
+ * Reads the MIN_PERF register and converts the performance value to
+ * frequency (kHz).
+ */
+static ssize_t show_min_perf(struct cpufreq_policy *policy, char *buf)
+{
+	struct cppc_cpudata *cpu_data = policy->driver_data;
+	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
+	u64 perf;
+	int ret;
+
+	ret = cppc_get_min_perf(policy->cpu, &perf);
+	if (ret == -EOPNOTSUPP)
+		return sysfs_emit(buf, "<unsupported>\n");
+	if (ret)
+		return ret;
+
+	/* Use lowest_perf if register is uninitialized (0) */
+	if (perf == 0)
+		perf = caps->lowest_perf;
+
+	/* Convert performance to frequency (kHz) for user */
+	return sysfs_emit(buf, "%u\n", cppc_perf_to_khz(caps, perf));
+}
+
+/**
+ * store_min_perf - Set minimum performance from frequency (kHz)
+ * @policy: cpufreq policy
+ * @buf: buffer containing the frequency value
+ * @count: size of @buf
+ *
+ * Converts the user-provided frequency (kHz) to a performance value
+ * and writes it to the MIN_PERF register.
+ */
+static ssize_t store_min_perf(struct cpufreq_policy *policy, const char *buf,
+			      size_t count)
+{
+	struct cppc_cpudata *cpu_data = policy->driver_data;
+	unsigned int freq_khz;
+	u64 perf;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &freq_khz);
+	if (ret)
+		return ret;
+
+	/* Convert frequency (kHz) to performance value */
+	perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
+
+	guard(mutex)(&cppc_cpufreq_autonomous_lock);
+	ret = cppc_cpufreq_set_mperf_reg(policy, perf, true);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+/**
+ * show_max_perf - Show maximum performance as frequency (kHz)
+ * @policy: cpufreq policy
+ * @buf: buffer to write the frequency value to
+ *
+ * Reads the MAX_PERF register and converts the performance value to
+ * frequency (kHz).
+ */
+static ssize_t show_max_perf(struct cpufreq_policy *policy, char *buf)
+{
+	struct cppc_cpudata *cpu_data = policy->driver_data;
+	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
+	u64 perf;
+	int ret;
+
+	ret = cppc_get_max_perf(policy->cpu, &perf);
+	if (ret == -EOPNOTSUPP)
+		return sysfs_emit(buf, "<unsupported>\n");
+	if (ret)
+		return ret;
+
+	/* Use highest_perf if register is uninitialized or out of range */
+	if (perf == 0 || perf > caps->highest_perf)
+		perf = caps->highest_perf;
+
+	/* Convert performance to frequency (kHz) for user */
+	return sysfs_emit(buf, "%u\n", cppc_perf_to_khz(caps, perf));
+}
+
+/**
+ * store_max_perf - Set maximum performance from frequency (kHz)
+ * @policy: cpufreq policy
+ * @buf: buffer containing the frequency value
+ * @count: size of @buf
+ *
+ * Converts the user-provided frequency (kHz) to a performance value
+ * and writes it to the MAX_PERF register.
+ */
+static ssize_t store_max_perf(struct cpufreq_policy *policy, const char *buf,
+			      size_t count)
+{
+	struct cppc_cpudata *cpu_data = policy->driver_data;
+	unsigned int freq_khz;
+	u64 perf;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &freq_khz);
+	if (ret)
+		return ret;
+
+	/* Convert frequency (kHz) to performance value */
+	perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
+
+	guard(mutex)(&cppc_cpufreq_autonomous_lock);
+	ret = cppc_cpufreq_set_mperf_reg(policy, perf, false);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
 cpufreq_freq_attr_ro(freqdomain_cpus);
 cpufreq_freq_attr_rw(auto_select);
 cpufreq_freq_attr_rw(auto_act_window);
 cpufreq_freq_attr_rw(energy_performance_preference_val);
+cpufreq_freq_attr_rw(min_perf);
+cpufreq_freq_attr_rw(max_perf);
 
 static struct freq_attr *cppc_cpufreq_attr[] = {
 	&freqdomain_cpus,
 	&auto_select,
 	&auto_act_window,
 	&energy_performance_preference_val,
+	&min_perf,
+	&max_perf,
 	NULL,
 };
 
diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
index 3fc796c0d902..b358440cd0e2 100644
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -174,6 +174,10 @@ extern int cppc_get_auto_act_window(int cpu, u64 *auto_act_window);
 extern int cppc_set_auto_act_window(int cpu, u64 auto_act_window);
 extern int cppc_get_auto_sel(int cpu, bool *enable);
 extern int cppc_set_auto_sel(int cpu, bool enable);
+extern int cppc_get_min_perf(int cpu, u64 *min_perf);
+extern int cppc_set_min_perf(int cpu, u32 min_perf);
+extern int cppc_get_max_perf(int cpu, u64 *max_perf);
+extern int cppc_set_max_perf(int cpu, u32 max_perf);
 extern int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf);
 extern int amd_get_boost_ratio_numerator(unsigned int cpu, u64 *numerator);
 extern int amd_detect_prefcore(bool *detected);
@@ -270,6 +274,22 @@ static inline int cppc_set_auto_sel(int cpu, bool enable)
 {
 	return -EOPNOTSUPP;
 }
+static inline int cppc_get_min_perf(int cpu, u64 *min_perf)
+{
+	return -EOPNOTSUPP;
+}
+static inline int cppc_set_min_perf(int cpu, u32 min_perf)
+{
+	return -EOPNOTSUPP;
+}
+static inline int cppc_get_max_perf(int cpu, u64 *max_perf)
+{
+	return -EOPNOTSUPP;
+}
+static inline int cppc_set_max_perf(int cpu, u32 max_perf)
+{
+	return -EOPNOTSUPP;
+}
 static inline int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf)
 {
 	return -ENODEV;
-- 
2.34.1

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