ACPI: CPPC: Add CPPC enable register function

Add a new function to enable CPPC feature. This function
will write Continuous Performance Control package
EnableRegister field on the processor.

CPPC EnableRegister register described in section 8.4.7.1 of ACPI 6.4:
This element is optional. If supported, contains a resource descriptor
with a single Register() descriptor that describes a register to which
OSPM writes a One to enable CPPC on this processor. Before this register
is set, the processor will be controlled by legacy mechanisms (ACPI
Pstates, firmware, etc.).

This register will be used for AMD processors to enable AMD P-State
function instead of legacy ACPI P-States.

Signed-off-by: Jinzhou Su <Jinzhou.Su@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index cc790037d643..e4fd5a8237e2 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1276,6 +1276,51 @@ out_err:
 EXPORT_SYMBOL_GPL(cppc_get_perf_ctrs);
 
 /**
+ * cppc_set_enable - Set to enable CPPC on the processor by writing the
+ * Continuous Performance Control package EnableRegister field.
+ * @cpu: CPU for which to enable CPPC register.
+ * @enable: 0 - disable, 1 - enable CPPC feature on the processor.
+ *
+ * Return: 0 for success, -ERRNO or -EIO otherwise.
+ */
+int cppc_set_enable(int cpu, bool enable)
+{
+	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
+	struct cpc_register_resource *enable_reg;
+	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
+	struct cppc_pcc_data *pcc_ss_data = NULL;
+	int ret = -EINVAL;
+
+	if (!cpc_desc) {
+		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
+		return -EINVAL;
+	}
+
+	enable_reg = &cpc_desc->cpc_regs[ENABLE];
+
+	if (CPC_IN_PCC(enable_reg)) {
+
+		if (pcc_ss_id < 0)
+			return -EIO;
+
+		ret = cpc_write(cpu, enable_reg, enable);
+		if (ret)
+			return ret;
+
+		pcc_ss_data = pcc_data[pcc_ss_id];
+
+		down_write(&pcc_ss_data->pcc_lock);
+		/* after writing CPC, transfer the ownership of PCC to platfrom */
+		ret = send_pcc_cmd(pcc_ss_id, CMD_WRITE);
+		up_write(&pcc_ss_data->pcc_lock);
+		return ret;
+	}
+
+	return cpc_write(cpu, enable_reg, enable);
+}
+EXPORT_SYMBOL_GPL(cppc_set_enable);
+
+/**
  * cppc_set_perf - Set a CPU's performance controls.
  * @cpu: CPU for which to set performance controls.
  * @perf_ctrls: ptr to cppc_perf_ctrls. See cppc_acpi.h