Re: [PATCH 6/7] cpufreq: amd_pstate: implement amd pstate cpu online and offline callback

From: Limonciello, Mario
Date: Fri Sep 09 2022 - 15:03:12 EST


On 9/9/2022 11:45, Perry Yuan wrote:
The patch adds online and offline driver callback to support to allow cpu cores go
offline and help to restore the previous working states when core goes
back online later for EPP driver mode.

Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
---
drivers/cpufreq/amd-pstate.c | 93 +++++++++++++++++++++++++++++++++++-
1 file changed, 92 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index e71b06e20050..e63fed39f90c 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -111,7 +111,8 @@ struct amd_aperf_mperf {
* @cppc_cap1_cached: Cached value of the last CPPC Capabilities MSR
* @update_util: Cpufreq utility callback information
* @sample: the stored performance sample
-
+ * @suspended: Whether or not the driver has been suspended.
+ *
* The amd_cpudata is key private data for each CPU thread in AMD P-State, and
* represents all the attributes and goals that AMD P-State requests at runtime.
*/
@@ -151,6 +152,7 @@ struct amd_cpudata {
u64 cppc_cap1_cached;
struct update_util_data update_util;
struct amd_aperf_mperf sample;
+ bool suspended;
};
/**
@@ -1387,6 +1389,93 @@ static int amd_pstate_epp_set_policy(struct cpufreq_policy *policy)
return 0;
}
+static void amd_pstate_epp_reenable(struct amd_cpudata * cpudata)
+{
+ struct cppc_perf_ctrls perf_ctrls;
+ u64 value, max_perf;
+ int ret;
+
+ ret = amd_pstate_enable(true);
+ if (ret)
+ pr_err("failed to enable amd pstate during resume, return %d\n", ret);

As this driver uses pr_fmt, this doesn't need to be as verbose. Look at my comments in patch 7/7 and you can adopt the same here.

+
+ value = READ_ONCE(cpudata->cppc_req_cached);
+ max_perf = READ_ONCE(cpudata->highest_perf);
+
+ if (boot_cpu_has(X86_FEATURE_CPPC)) {
+ wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
+ } else {
+ perf_ctrls.max_perf = max_perf;
+ perf_ctrls.energy_perf = AMD_CPPC_ENERGY_PERF_PREF(cpudata->epp_cached);
+ cppc_set_perf(cpudata->cpu, &perf_ctrls);
+ }
+}
+
+static int amd_pstate_epp_cpu_online(struct cpufreq_policy *policy)
+{
+ struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
+
+ pr_debug("AMD CPU Core %d going online\n", cpudata->cpu);
+
+ if (epp_enabled) {
+ amd_pstate_epp_reenable(cpudata);
+ cpudata->suspended = false;
+ }
+
+ return 0;
+}
+
+static void amd_pstate_epp_offline(struct cpufreq_policy *policy)
+{
+ struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
+ struct cppc_perf_ctrls perf_ctrls;
+ int min_perf;
+ u64 value;
+
+ min_perf = READ_ONCE(cpudata->lowest_perf);
+ value = READ_ONCE(cpudata->cppc_req_cached);
+
+ mutex_lock(&amd_pstate_limits_lock);
+ if (boot_cpu_has(X86_FEATURE_CPPC)) {
+ cpudata->epp_policy = CPUFREQ_POLICY_UNKNOWN;
+
+ /* Set max perf same as min perf */
+ value &= ~AMD_CPPC_MAX_PERF(~0L);
+ value |= AMD_CPPC_MAX_PERF(min_perf);
+ value &= ~AMD_CPPC_MIN_PERF(~0L);
+ value |= AMD_CPPC_MIN_PERF(min_perf);
+ wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
+ } else {
+ perf_ctrls.desired_perf = 0;
+ perf_ctrls.max_perf = min_perf;
+ perf_ctrls.energy_perf = AMD_CPPC_ENERGY_PERF_PREF(AMD_CPPC_EPP_POWERSAVE);
+ cppc_set_perf(cpudata->cpu, &perf_ctrls);
+ }
+ mutex_unlock(&amd_pstate_limits_lock);
+}
+
+static int amd_pstate_cpu_offline(struct cpufreq_policy *policy)
+{
+ struct amd_cpudata *cpudata = all_cpu_data[policy->cpu];
+
+ pr_debug("AMD CPU Core %d going offline\n", cpudata->cpu); > +
+ if (cpudata->suspended)
+ return 0;
+
+ if (epp_enabled)
+ amd_pstate_epp_offline(policy);
+
+ return 0;
+}
+
+static int amd_pstate_epp_cpu_offline(struct cpufreq_policy *policy)
+{
+ amd_pstate_clear_update_util_hook(policy->cpu);
+
+ return amd_pstate_cpu_offline(policy);
+}
+
static void amd_pstate_verify_cpu_policy(struct amd_cpudata *cpudata,
struct cpufreq_policy_data *policy)
{
@@ -1421,6 +1510,8 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
.init = amd_pstate_epp_cpu_init,
.exit = amd_pstate_epp_cpu_exit,
.update_limits = amd_pstate_epp_update_limits,
+ .offline = amd_pstate_epp_cpu_offline,
+ .online = amd_pstate_epp_cpu_online,
.name = "amd_pstate_epp",
.attr = amd_pstate_epp_attr,
};