[PATCH v2 7/7] acpi/cppc: Add support for CPPC Enable register

[Natarajan, Janakarajan]

From: Yazen Ghannam <Yazen.Ghannam@xxxxxxx>

To enable CPPC on a processor, the OS should write a value "1" to the
CPPC Enable register. Add support for this register.

Signed-off-by: Yazen Ghannam <Yazen.Ghannam@xxxxxxx>
[ carved out into a patch, cleaned up, productized ]
Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@xxxxxxx>
---
 drivers/acpi/cppc_acpi.c | 96 ++++++++++++++++++++++++++++++++++++++++
 include/acpi/cppc_acpi.h |  1 +
 2 files changed, 97 insertions(+)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index bb57d526e54e..b74c489a3e8d 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -232,6 +232,43 @@ static ssize_t show_feedback_ctrs(struct kobject *kobj,
 }
 define_one_cppc_ro(feedback_ctrs);
 
+/* Used to move ENABLE register value between userspace and platform */
+static bool cppc_cpu_enable;
+
+static ssize_t show_enable(struct kobject *kobj,
+			   struct attribute *attr,
+			   char *buf)
+{
+	struct cpc_desc *cpc_ptr = to_cpc_desc(kobj);
+	int ret;
+
+	ret = cppc_get_enable(cpc_ptr->cpu_id);
+	if (ret)
+		return ret;
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", cppc_cpu_enable);
+}
+
+static ssize_t store_enable(struct kobject *kobj,
+			    struct attribute *attr,
+			    const char *c, ssize_t count)
+{
+	struct cpc_desc *cpc_ptr = to_cpc_desc(kobj);
+	int ret;
+
+	ret = kstrtobool(c, &cppc_cpu_enable);
+	if (ret)
+		return ret;
+
+	ret = cppc_set_reg(cpc_ptr->cpu_id, NULL, ENABLE);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+define_one_cppc_rw(enable);
+
 static struct kobj_type cppc_ktype = {
 	.sysfs_ops = &kobj_sysfs_ops,
 };
@@ -826,6 +863,9 @@ static int set_cppc_attrs(struct cpc_desc *cpc, int entries)
 		case DESIRED_PERF:
 			cppc_attrs[attr_i++] = &desired_perf.attr;
 			break;
+		case ENABLE:
+			cppc_attrs[attr_i++] = &enable.attr;
+			break;
 		}
 	}
 
@@ -1426,6 +1466,9 @@ int cppc_set_reg(int cpu, struct cppc_perf_ctrls *perf_ctrls,
 	}
 
 	switch (reg_idx) {
+	case ENABLE:
+		value = cppc_cpu_enable;
+		break;
 	case DESIRED_PERF:
 		value = perf_ctrls->desired_perf;
 		break;
@@ -1616,6 +1659,59 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 }
 EXPORT_SYMBOL_GPL(cppc_get_perf);
 
+/**
+ * cppc_get_enable - Read a CPUs enable register.
+ * @cpu: CPU from which to read control values.
+ *
+ * Return: 0 for success.
+ */
+int cppc_get_enable(int cpu)
+{
+	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
+	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
+	struct cpc_register_resource *enable_reg;
+	struct cppc_pcc_data *pcc_ss_data = NULL;
+	int ret = 0, regs_in_pcc = 0;
+	u64 enable;
+
+	if (!cpc_desc) {
+		pr_debug("No CPC descriptor for CPU: %d\n", cpu);
+		return -ENODEV;
+	}
+
+	enable_reg = &cpc_desc->cpc_regs[ENABLE];
+
+	if (!CPC_SUP_BUFFER_ONLY(enable_reg)) {
+		pr_warn("CPC ENABLE register not supported.\n");
+		return -ENOTSUPP;
+	}
+
+	if (CPC_IN_PCC(enable_reg)) {
+		pcc_ss_data = pcc_data[pcc_ss_id];
+		down_write(&pcc_ss_data->pcc_lock);
+		regs_in_pcc = 1;
+		/* Ring doorbell once to update PCC subspace */
+		if (send_pcc_cmd(pcc_ss_id, CMD_READ) < 0) {
+			ret = -EIO;
+			goto out_err;
+		}
+	}
+
+	if (cpc_read(cpu, enable_reg, &enable)) {
+		ret = -EFAULT;
+		goto out_err;
+	}
+
+	cppc_cpu_enable = enable;
+
+out_err:
+	if (regs_in_pcc)
+		up_write(&pcc_ss_data->pcc_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cppc_get_enable);
+
 /**
  * cppc_get_transition_latency - returns frequency transition latency in ns
  *
diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
index 6f651235933c..fcdedff8e6bd 100644
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -139,6 +139,7 @@ struct cppc_cpudata {
 	cpumask_var_t shared_cpu_map;
 };
 
+extern int cppc_get_enable(int cpu);
 extern int cppc_get_desired_perf(int cpunum, u64 *desired_perf);
 extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs);
 extern int cppc_set_reg(int cpu, struct cppc_perf_ctrls *perf_ctrls, enum cppc_regs reg_idx);
-- 
2.17.1