[PATCH v2 2/2] ACPI: CPPC: Add ospm_nominal_perf support

[Sumit Gupta <sumitg@nvidia.com>]

Add acpi_cppc/ospm_nominal_perf sysfs attribute (read-write) and
cppc_set_ospm_nominal_perf() API for the OSPM Nominal Performance
register (ACPI 6.6, Section 8.4.6.1.2.6).

The register conveys the desired nominal performance level at which
the platform may run. OSPM can request a lower level than platform
nominal. Valid range is [Lowest Performance, Nominal Performance].
The value tells the platform what OSPM considers nominal. The
platform classifies performance above this as boosted and below as
throttled. It uses that for its power/thermal decisions.

Although the register is write-only per spec, cache the OSPM-written
value in cpc_desc so userspace can observe it via sysfs, and to
skip redundant writes.

Initialize to platform nominal at policy init. Override via sysfs
if needed.

Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
---
 drivers/acpi/cppc_acpi.c       | 69 ++++++++++++++++++++++++++++++++++
 drivers/cpufreq/cppc_cpufreq.c | 10 +++++
 include/acpi/cppc_acpi.h       |  6 +++
 3 files changed, 85 insertions(+)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index a1c91ce20cc8..fbc620adafad 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -155,6 +155,10 @@ static DEFINE_PER_CPU(struct cpc_desc *, cpc_desc_ptr);
 static struct kobj_attribute _name =		\
 __ATTR(_name, 0444, show_##_name, NULL)
 
+#define define_one_cppc_rw(_name)		\
+static struct kobj_attribute _name =		\
+__ATTR(_name, 0644, show_##_name, store_##_name)
+
 #define to_cpc_desc(a) container_of(a, struct cpc_desc, kobj)
 
 #define show_cppc_data(access_fn, struct_name, member_name)		\
@@ -211,6 +215,38 @@ static ssize_t show_feedback_ctrs(struct kobject *kobj,
 }
 define_one_cppc_ro(feedback_ctrs);
 
+static ssize_t show_ospm_nominal_perf(struct kobject *kobj,
+				      struct kobj_attribute *attr, char *buf)
+{
+	struct cpc_desc *cpc_ptr = to_cpc_desc(kobj);
+	u64 val = READ_ONCE(cpc_ptr->ospm_nominal_perf);
+
+	if (!val)
+		return -ENODATA;
+
+	return sysfs_emit(buf, "%llu\n", val);
+}
+
+static ssize_t store_ospm_nominal_perf(struct kobject *kobj,
+				       struct kobj_attribute *attr,
+				       const char *buf, size_t count)
+{
+	struct cpc_desc *cpc_ptr = to_cpc_desc(kobj);
+	u64 val;
+	int ret;
+
+	ret = kstrtou64(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	ret = cppc_set_ospm_nominal_perf(cpc_ptr->cpu_id, val);
+	if (ret)
+		return ret;
+
+	return count;
+}
+define_one_cppc_rw(ospm_nominal_perf);
+
 static struct attribute *cppc_attrs[] = {
 	&feedback_ctrs.attr,
 	&reference_perf.attr,
@@ -222,6 +258,7 @@ static struct attribute *cppc_attrs[] = {
 	&nominal_perf.attr,
 	&nominal_freq.attr,
 	&lowest_freq.attr,
+	&ospm_nominal_perf.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(cppc);
@@ -1683,6 +1720,38 @@ int cppc_set_epp(int cpu, u64 epp_val)
 }
 EXPORT_SYMBOL_GPL(cppc_set_epp);
 
+/**
+ * cppc_set_ospm_nominal_perf() - Write OSPM Nominal Performance register.
+ * @cpu: CPU on which to write register.
+ * @ospm_nominal_perf: Value to write to the OSPM Nominal Performance register.
+ *
+ * OSPM Nominal Performance allows OSPM to inform the platform of the nominal
+ * performance level it intends to maintain.
+ *
+ * Return: 0 for success, -EINVAL on invalid input, -EOPNOTSUPP if not
+ * supported, -EIO otherwise.
+ */
+int cppc_set_ospm_nominal_perf(int cpu, u64 ospm_nominal_perf)
+{
+	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
+	int ret;
+
+	if (!ospm_nominal_perf || ospm_nominal_perf > U32_MAX)
+		return -EINVAL;
+
+	if (cpc_desc &&
+	    READ_ONCE(cpc_desc->ospm_nominal_perf) == ospm_nominal_perf)
+		return 0;
+
+	ret = cppc_set_reg_val(cpu, OSPM_NOMINAL_PERF, ospm_nominal_perf);
+	if (ret)
+		return ret;
+
+	WRITE_ONCE(cpc_desc->ospm_nominal_perf, ospm_nominal_perf);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(cppc_set_ospm_nominal_perf);
+
 /**
  * cppc_get_auto_act_window() - Read autonomous activity window register.
  * @cpu: CPU from which to read register.
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 7e7f9dfb7a24..d06cba963550 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -715,6 +715,16 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
 		goto out;
 	}
 
+	/*
+	 * Initialize OSPM Nominal Performance to inform firmware of
+	 * OSPM's nominal level. Performance above this value = boost;
+	 * below = throttle. Uses platform nominal by default.
+	 */
+	ret = cppc_set_ospm_nominal_perf(cpu, caps->nominal_perf);
+	if (ret && ret != -EOPNOTSUPP)
+		pr_debug("Failed to set ospm_nominal_perf for CPU%d: %d\n",
+			 cpu, ret);
+
 	cppc_cpufreq_cpu_fie_init(policy);
 	return 0;
 
diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
index 8693890a7275..3771e2ed507d 100644
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -86,6 +86,7 @@ struct cpc_desc {
 	struct cpc_register_resource cpc_regs[MAX_CPC_REG_ENT];
 	struct acpi_psd_package domain_info;
 	struct kobject kobj;
+	u32 ospm_nominal_perf;
 };
 
 /* These are indexes into the per-cpu cpc_regs[]. Order is important. */
@@ -180,6 +181,7 @@ extern int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val);
 extern int cppc_get_epp_perf(int cpunum, u64 *epp_perf);
 extern int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable);
 extern int cppc_set_epp(int cpu, u64 epp_val);
+extern int cppc_set_ospm_nominal_perf(int cpu, u64 ospm_nominal_perf);
 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);
@@ -266,6 +268,10 @@ static inline int cppc_set_epp(int cpu, u64 epp_val)
 {
 	return -EOPNOTSUPP;
 }
+static inline int cppc_set_ospm_nominal_perf(int cpu, u64 ospm_nominal_perf)
+{
+	return -EOPNOTSUPP;
+}
 static inline int cppc_get_auto_act_window(int cpu, u64 *auto_act_window)
 {
 	return -EOPNOTSUPP;
-- 
2.34.1