[PATCH v2 04/17] cpufreq/amd-pstate: Overhaul locking

Mario Limonciello
2025-02-15T00:53:00Z

amd_pstate_cpu_boost_update() and refresh_frequency_limits() both
update the policy state and have nothing to do with the amd-pstate
driver itself.

A global "limits" lock doesn't make sense because each CPU can have
policies changed independently. Each time a CPU changes values they
will atomically be written to the per-CPU perf member. Drop per CPU
locking cases.

The remaining "global" driver lock is used to ensure that only one
entity can change driver modes at a given time.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
drivers/cpufreq/amd-pstate.c | 13 +++----------
1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 8c3b54030ec56..044091806f14f 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -196,7 +196,6 @@ static inline int get_mode_idx_from_str(const char *str, size_t size)
return -EINVAL;
}

-static DEFINE_MUTEX(amd_pstate_limits_lock);
static DEFINE_MUTEX(amd_pstate_driver_lock);

static u8 msr_get_epp(struct amd_cpudata *cpudata)
@@ -752,7 +751,6 @@ static int amd_pstate_set_boost(struct cpufreq_policy *policy, int state)
pr_err("Boost mode is not supported by this processor or SBIOS\n");
return -EOPNOTSUPP;
}
- guard(mutex)(&amd_pstate_driver_lock);

ret = amd_pstate_cpu_boost_update(policy, state);
refresh_frequency_limits(policy);
@@ -1172,8 +1170,6 @@ static ssize_t store_energy_performance_preference(
if (ret < 0)
return -EINVAL;

- guard(mutex)(&amd_pstate_limits_lock);
-
ret = amd_pstate_set_energy_pref_index(policy, ret);

return ret ? ret : count;
@@ -1346,8 +1342,10 @@ int amd_pstate_update_status(const char *buf, size_t size)
if (mode_idx < 0 || mode_idx >= AMD_PSTATE_MAX)
return -EINVAL;

- if (mode_state_machine[cppc_state][mode_idx])
+ if (mode_state_machine[cppc_state][mode_idx]) {
+ guard(mutex)(&amd_pstate_driver_lock);
return mode_state_machine[cppc_state][mode_idx](mode_idx);
+ }

return 0;
}
@@ -1368,7 +1366,6 @@ static ssize_t status_store(struct device *a, struct device_attribute *b,
char *p = memchr(buf, '\n', count);
int ret;

- guard(mutex)(&amd_pstate_driver_lock);
ret = amd_pstate_update_status(buf, p ? p - buf : count);

return ret < 0 ? ret : count;
@@ -1640,8 +1637,6 @@ static int amd_pstate_epp_cpu_offline(struct cpufreq_policy *policy)
if (cpudata->suspended)
return 0;

- guard(mutex)(&amd_pstate_limits_lock);
-
if (trace_amd_pstate_epp_perf_enabled()) {
trace_amd_pstate_epp_perf(cpudata->cpu, perf.highest_perf,
AMD_CPPC_EPP_BALANCE_POWERSAVE,
@@ -1678,8 +1673,6 @@ static int amd_pstate_epp_resume(struct cpufreq_policy *policy)
struct amd_cpudata *cpudata = policy->driver_data;

if (cpudata->suspended) {
- guard(mutex)(&amd_pstate_limits_lock);
-
/* enable amd pstate from suspend state*/
amd_pstate_epp_reenable(policy);

--
2.43.0