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Message-ID: <20250421080444.707538-3-dhananjay.ugwekar@amd.com>
Date: Mon, 21 Apr 2025 08:04:47 +0000
From: Dhananjay Ugwekar <dhananjay.ugwekar@....com>
To: <gautham.shenoy@....com>, <mario.limonciello@....com>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Dhananjay
Ugwekar" <dhananjay.ugwekar@....com>
Subject: [PATCH v2 2/2] cpufreq/amd-pstate: Add support for the "Requested CPU Min frequency" BIOS option
Initialize lower frequency limit to the "Requested CPU Min frequency"
BIOS option (if it is set) value as part of the driver->init()
callback. The BIOS specified value is passed by the PMFW as min_perf in
CPPC_REQ MSR.
To ensure that we don't mistake a stale min_perf value in CPPC_REQ
value as the "Requested CPU Min frequency" during a kexec wakeup, reset
the CPPC_REQ.min_perf value back to the BIOS specified one in the offline,
exit and suspend callbacks. amd_pstate_target() and
amd_pstate_epp_update_limit() which are invoked as part of the resume()
and online() callbacks will take care of restoring the CPPC_REQ back to
the latest sane values.
Signed-off-by: Dhananjay Ugwekar <dhananjay.ugwekar@....com>
---
Changes in v2:
* Modify the condition in msr_init_perf to initialize perf.bios_min_perf
to 0 by default
* Use READ_ONCE to read cpudata->perf in exit, suspend and offline
callbacks
---
drivers/cpufreq/amd-pstate.c | 67 +++++++++++++++++++++++++++++-------
drivers/cpufreq/amd-pstate.h | 2 ++
2 files changed, 56 insertions(+), 13 deletions(-)
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 02de51001eba..407fdd31fb0b 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -389,7 +389,8 @@ static inline int amd_pstate_cppc_enable(struct cpufreq_policy *policy)
static int msr_init_perf(struct amd_cpudata *cpudata)
{
union perf_cached perf = READ_ONCE(cpudata->perf);
- u64 cap1, numerator;
+ u64 cap1, numerator, cppc_req;
+ u8 min_perf;
int ret = rdmsrl_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1,
&cap1);
@@ -400,6 +401,22 @@ static int msr_init_perf(struct amd_cpudata *cpudata)
if (ret)
return ret;
+ ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &cppc_req);
+ if (ret)
+ return ret;
+
+ WRITE_ONCE(cpudata->cppc_req_cached, cppc_req);
+ min_perf = FIELD_GET(AMD_CPPC_MIN_PERF_MASK, cppc_req);
+
+ /*
+ * Clear out the min_perf part to check if the rest of the MSR is 0, if yes, this is an
+ * indication that the min_perf value is the one specified through the BIOS option
+ */
+ cppc_req &= ~(AMD_CPPC_MIN_PERF_MASK);
+
+ if (!cppc_req)
+ perf.bios_min_perf = min_perf;
+
perf.highest_perf = numerator;
perf.max_limit_perf = numerator;
perf.min_limit_perf = FIELD_GET(AMD_CPPC_LOWEST_PERF_MASK, cap1);
@@ -580,20 +597,26 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy_data)
{
/*
* Initialize lower frequency limit (i.e.policy->min) with
- * lowest_nonlinear_frequency which is the most energy efficient
- * frequency. Override the initial value set by cpufreq core and
- * amd-pstate qos_requests.
+ * lowest_nonlinear_frequency or the min frequency (if) specified in BIOS,
+ * Override the initial value set by cpufreq core and amd-pstate qos_requests.
*/
if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
struct cpufreq_policy *policy __free(put_cpufreq_policy) =
cpufreq_cpu_get(policy_data->cpu);
struct amd_cpudata *cpudata;
+ union perf_cached perf;
if (!policy)
return -EINVAL;
cpudata = policy->driver_data;
- policy_data->min = cpudata->lowest_nonlinear_freq;
+ perf = READ_ONCE(cpudata->perf);
+
+ if (perf.bios_min_perf)
+ policy_data->min = perf_to_freq(perf, cpudata->nominal_freq,
+ perf.bios_min_perf);
+ else
+ policy_data->min = cpudata->lowest_nonlinear_freq;
}
cpufreq_verify_within_cpu_limits(policy_data);
@@ -1040,6 +1063,10 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
static void amd_pstate_cpu_exit(struct cpufreq_policy *policy)
{
struct amd_cpudata *cpudata = policy->driver_data;
+ union perf_cached perf = READ_ONCE(cpudata->perf);
+
+ /* Reset CPPC_REQ MSR to the BIOS value */
+ amd_pstate_update_perf(policy, perf.bios_min_perf, 0U, 0U, 0U, false);
freq_qos_remove_request(&cpudata->req[1]);
freq_qos_remove_request(&cpudata->req[0]);
@@ -1428,7 +1455,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
struct amd_cpudata *cpudata;
union perf_cached perf;
struct device *dev;
- u64 value;
int ret;
/*
@@ -1493,12 +1519,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
cpudata->epp_default = AMD_CPPC_EPP_BALANCE_PERFORMANCE;
}
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
- ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &value);
- if (ret)
- return ret;
- WRITE_ONCE(cpudata->cppc_req_cached, value);
- }
ret = amd_pstate_set_epp(policy, cpudata->epp_default);
if (ret)
return ret;
@@ -1518,6 +1538,11 @@ static void amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
struct amd_cpudata *cpudata = policy->driver_data;
if (cpudata) {
+ union perf_cached perf = READ_ONCE(cpudata->perf);
+
+ /* Reset CPPC_REQ MSR to the BIOS value */
+ amd_pstate_update_perf(policy, perf.bios_min_perf, 0U, 0U, 0U, false);
+
kfree(cpudata);
policy->driver_data = NULL;
}
@@ -1575,12 +1600,28 @@ static int amd_pstate_cpu_online(struct cpufreq_policy *policy)
static int amd_pstate_cpu_offline(struct cpufreq_policy *policy)
{
- return 0;
+ struct amd_cpudata *cpudata = policy->driver_data;
+ union perf_cached perf = READ_ONCE(cpudata->perf);
+
+ /*
+ * Reset CPPC_REQ MSR to the BIOS value, this will allow us to retain the BIOS specified
+ * min_perf value across kexec reboots. If this CPU is just onlined normally after this, the
+ * limits, epp and desired perf will get reset to the cached values in cpudata struct
+ */
+ return amd_pstate_update_perf(policy, perf.bios_min_perf, 0U, 0U, 0U, false);
}
static int amd_pstate_suspend(struct cpufreq_policy *policy)
{
struct amd_cpudata *cpudata = policy->driver_data;
+ union perf_cached perf = READ_ONCE(cpudata->perf);
+
+ /*
+ * Reset CPPC_REQ MSR to the BIOS value, this will allow us to retain the BIOS specified
+ * min_perf value across kexec reboots. If this CPU is just resumed back without kexec,
+ * the limits, epp and desired perf will get reset to the cached values in cpudata struct
+ */
+ amd_pstate_update_perf(policy, perf.bios_min_perf, 0U, 0U, 0U, false);
/* invalidate to ensure it's rewritten during resume */
cpudata->cppc_req_cached = 0;
diff --git a/drivers/cpufreq/amd-pstate.h b/drivers/cpufreq/amd-pstate.h
index fbe1c08d3f06..2f7ae364d331 100644
--- a/drivers/cpufreq/amd-pstate.h
+++ b/drivers/cpufreq/amd-pstate.h
@@ -30,6 +30,7 @@
* @lowest_perf: the absolute lowest performance level of the processor
* @min_limit_perf: Cached value of the performance corresponding to policy->min
* @max_limit_perf: Cached value of the performance corresponding to policy->max
+ * @bios_min_perf: Cached perf value corresponding to the "Requested CPU Min Frequency" BIOS option
*/
union perf_cached {
struct {
@@ -39,6 +40,7 @@ union perf_cached {
u8 lowest_perf;
u8 min_limit_perf;
u8 max_limit_perf;
+ u8 bios_min_perf;
};
u64 val;
};
--
2.34.1
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