[PATCH v3 1/2] cpufreq: CPPC: Set CPPC Enable register in cpu_init

[Sumit Gupta]

As per ACPI 6.x s8.4.6.1.4 (CPPC Enable register):
  "If supported by the platform, OSPM writes a one to this register
   to enable CPPC on this processor. If not implemented, OSPM assumes
   the platform always has CPPC enabled."

Call cppc_set_enable() at the start of cppc_cpufreq_cpu_init() so
this is done for both OS-driven and autonomous CPPC control modes.
Errors are logged but non-fatal as the register is optional.

Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
---
 drivers/cpufreq/cppc_cpufreq.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index c1ba6c656f61..6b54427b52e1 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -655,6 +655,14 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	caps = &cpu_data->perf_caps;
 	policy->driver_data = cpu_data;
 
+	/*
+	 * Enable CPPC for both OS-driven and autonomous modes.
+	 * The Enable register is optional - some platforms may not support it
+	 */
+	ret = cppc_set_enable(cpu, true);
+	if (ret && ret != -EOPNOTSUPP)
+		pr_warn("Failed to enable CPPC for CPU%d (%d)\n", cpu, ret);
+
 	/*
 	 * Set min to lowest nonlinear perf to avoid any efficiency penalty (see
 	 * Section 8.4.7.1.1.5 of ACPI 6.1 spec)
-- 
2.34.1