[PATCH v8 08/13] cpufreq: amd-pstate: implement suspend and resume callbacks

[Perry Yuan <perry.yuan@amd.com>]

From: Perry Yuan <Perry.Yuan@amd.com>

add suspend and resume support for the AMD processors by amd_pstate_epp
driver instance.

When the CPPC is suspended, EPP driver will set EPP profile to 'power'
profile and set max/min perf to lowest perf value.
When resume happens, it will restore the MSR registers with
previous cached value.

Reviewed-by: Mario Limonciello <Mario.Limonciello@amd.com>
Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
---
 drivers/cpufreq/amd-pstate.c | 41 ++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index cb647f55a169..fc12d35bc7bd 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1107,6 +1107,45 @@ static int amd_pstate_epp_verify_policy(struct cpufreq_policy_data *policy)
 	return 0;
 }
 
+static int amd_pstate_epp_suspend(struct cpufreq_policy *policy)
+{
+        struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
+        int ret;
+
+        /* avoid suspending when EPP is not enabled */
+        if (cppc_state != AMD_PSTATE_ACTIVE)
+                return 0;
+
+        /* set this flag to avoid setting core offline*/
+        cpudata->suspended = true;
+
+        /* disable CPPC in lowlevel firmware */
+        ret = amd_pstate_enable(false);
+        if (ret)
+                pr_err("failed to suspend, return %d\n", ret);
+
+        return 0;
+}
+
+static int amd_pstate_epp_resume(struct cpufreq_policy *policy)
+{
+        struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
+
+        if (cpudata->suspended) {
+                mutex_lock(&amd_pstate_limits_lock);
+
+                /* enable amd pstate from suspend state*/
+                amd_pstate_epp_reenable(cpudata);
+
+                mutex_unlock(&amd_pstate_limits_lock);
+
+                cpudata->suspended = false;
+        }
+
+        return 0;
+}
+
+
 static struct cpufreq_driver amd_pstate_driver = {
 	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
 	.verify		= amd_pstate_verify,
@@ -1129,6 +1168,8 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
 	.update_limits	= amd_pstate_epp_update_limits,
 	.offline	= amd_pstate_epp_cpu_offline,
 	.online		= amd_pstate_epp_cpu_online,
+	.suspend	= amd_pstate_epp_suspend,
+	.resume		= amd_pstate_epp_resume,
 	.name		= "amd_pstate_epp",
 	.attr		= amd_pstate_epp_attr,
 };
-- 
2.34.1