linux-kernel - [PATCH v2] cpufreq/amd-pstate: Write CPPC enable bit per-socket

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Date:   Tue, 30 May 2023 13:13:48 +0000
From:   Wyes Karny <wyes.karny@....com>
To:     <ray.huang@....com>, <rafael@...nel.org>, <viresh.kumar@...aro.org>
CC:     <Mario.Limonciello@....com>, <Perry.Yuan@....com>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Wyes Karny <wyes.karny@....com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>
Subject: [PATCH v2] cpufreq/amd-pstate: Write CPPC enable bit per-socket

Currently amd_pstate sets CPPC enable bit in MSR_AMD_CPPC_ENABLE only
for the CPU where the module_init happened. But MSR_AMD_CPPC_ENABLE is
per-socket. This causes CPPC enable bit to set for only one socket for
servers with more than one physical packages. To fix this write
MSR_AMD_CPPC_ENABLE per-socket.

Also, handle duplicate calls for cppc_enable, because it's called from
per-policy/per-core callbacks and can result in duplicate MSR writes.

Before the fix:
amd@amd:~$ sudo rdmsr -a 0xc00102b1 | uniq --count
	192 0
    192 1

After the fix:
amd@amd:~$ sudo rdmsr -a 0xc00102b1 | uniq --count
    384 1

Suggested-by: Gautham R. Shenoy <gautham.shenoy@....com>
Signed-off-by: Wyes Karny <wyes.karny@....com>
---
v1 -> v2:
- Made CPPC enable read/write per-socket

 drivers/cpufreq/amd-pstate.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 5a3d4aa0f45a..45b9e359f638 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -63,6 +63,7 @@ static struct cpufreq_driver *current_pstate_driver;
 static struct cpufreq_driver amd_pstate_driver;
 static struct cpufreq_driver amd_pstate_epp_driver;
 static int cppc_state = AMD_PSTATE_DISABLE;
+static bool cppc_enabled;
 
 /*
  * AMD Energy Preference Performance (EPP)
@@ -228,7 +229,28 @@ static int amd_pstate_set_energy_pref_index(struct amd_cpudata *cpudata,
 
 static inline int pstate_enable(bool enable)
 {
-	return wrmsrl_safe(MSR_AMD_CPPC_ENABLE, enable);
+	int ret, cpu;
+	unsigned long logical_proc_id_mask = 0;
+
+	if (enable == cppc_enabled)
+		return 0;
+
+	for_each_present_cpu(cpu) {
+		unsigned long logical_id = topology_logical_die_id(cpu);
+
+		if (test_bit(logical_id, &logical_proc_id_mask))
+			continue;
+
+		set_bit(logical_id, &logical_proc_id_mask);
+
+		ret = wrmsrl_safe_on_cpu(cpu, MSR_AMD_CPPC_ENABLE,
+				enable);
+		if (ret)
+			return ret;
+	}
+
+	cppc_enabled = enable;
+	return 0;
 }
 
 static int cppc_enable(bool enable)
@@ -236,6 +258,9 @@ static int cppc_enable(bool enable)
 	int cpu, ret = 0;
 	struct cppc_perf_ctrls perf_ctrls;
 
+	if (enable == cppc_enabled)
+		return 0;
+
 	for_each_present_cpu(cpu) {
 		ret = cppc_set_enable(cpu, enable);
 		if (ret)
@@ -251,6 +276,7 @@ static int cppc_enable(bool enable)
 		}
 	}
 
+	cppc_enabled = enable;
 	return ret;
 }
 
-- 
2.34.1