* [PATCH] cpufreq: CPPC: Preserve OSPM-set registers across hotplug and unload
@ 2026-06-23 9:54 Sumit Gupta
2026-06-23 11:00 ` Rafael J. Wysocki
0 siblings, 1 reply; 2+ messages in thread
From: Sumit Gupta @ 2026-06-23 9:54 UTC (permalink / raw)
To: rafael, viresh.kumar, pierre.gondois, ionela.voinescu,
zhenglifeng1, zhanjie9, linux-kernel, linux-pm, linux-tegra
Cc: treding, jonathanh, vsethi, ksitaraman, sanjayc, mochs, bbasu,
sumitg
Values written to OSPM-set CPPC registers (via sysfs or the autonomous
boot parameter) can be lost in two ways:
- Across CPU hotplug: the platform may reset a CPU's registers when it
is offlined.
- On driver unload: the value the driver wrote is left in the register
instead of returning to its pre-driver state.
Add a small table-driven mechanism that handles both:
- Capture each register's firmware value when a CPU is first seen and
restore it on driver unload.
- Record the last value the driver set and reapply it from ->init()
when the policy is reactivated after CPU hotplug.
The firmware value is captured on a CPU's first activation rather than
once at module load, so CPUs offline at boot or hot-added later are
covered.
Reapply is only needed on a full policy teardown and bring-up, which goes
through ->init(). In a SHARED_TYPE_ANY policy, offlining a single CPU
leaves the shared register untouched, so nothing is lost there.
Cover the OSPM Nominal Performance, Autonomous Selection
(auto_sel) and Energy Performance Preference (EPP) registers. For
auto_sel it replaces the previous unconditional
cppc_set_auto_sel(cpu, false) on unload with a restore of the firmware
value captured at the CPU's first init.
Suggested-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
---
This applies on top of (not yet merged):
[1] ACPI: CPPC: Add ospm_nominal_perf support
https://lore.kernel.org/lkml/20260615185934.2383514-1-sumitg@nvidia.com/
[2] cpufreq: CPPC: add autonomous mode boot parameter support
https://lore.kernel.org/lkml/20260623080652.3353386-1-sumitg@nvidia.com/
drivers/cpufreq/cppc_cpufreq.c | 194 +++++++++++++++++++++++++++++++--
1 file changed, 186 insertions(+), 8 deletions(-)
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index a3fabfb07fbe..d6ea2cbde187 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -28,6 +28,174 @@
static struct cpufreq_driver cppc_cpufreq_driver;
+/*
+ * OSPM-set CPPC registers tracked for save/restore. A value set via sysfs or
+ * the autonomous boot parameter is reapplied across CPU hotplug, and the
+ * firmware value is restored on driver unload.
+ */
+enum cppc_saved_reg_id {
+ CPPC_SAVED_OSPM_NOMINAL_PERF,
+ CPPC_SAVED_AUTO_SEL,
+ CPPC_SAVED_EPP,
+ CPPC_NR_SAVED_REGS,
+};
+
+struct cppc_saved_reg {
+ int (*get)(int cpu, u64 *val);
+ int (*set)(int cpu, u64 val);
+};
+
+/* u64 wrappers so the bool auto_sel register fits the table signatures. */
+static int cppc_get_auto_sel_u64(int cpu, u64 *val)
+{
+ bool enable;
+ int ret;
+
+ ret = cppc_get_auto_sel(cpu, &enable);
+ if (ret)
+ return ret;
+
+ *val = enable;
+ return 0;
+}
+
+static int cppc_set_auto_sel_u64(int cpu, u64 val)
+{
+ return cppc_set_auto_sel(cpu, !!val);
+}
+
+static const struct cppc_saved_reg cppc_saved_regs[CPPC_NR_SAVED_REGS] = {
+ [CPPC_SAVED_OSPM_NOMINAL_PERF] = {
+ cppc_get_ospm_nominal_perf, cppc_set_ospm_nominal_perf,
+ },
+ [CPPC_SAVED_AUTO_SEL] = {
+ cppc_get_auto_sel_u64, cppc_set_auto_sel_u64,
+ },
+ [CPPC_SAVED_EPP] = {
+ cppc_get_epp_perf, cppc_set_epp,
+ },
+};
+
+/*
+ * Per-CPU saved state for each register in cppc_saved_regs[]:
+ * firmware_val - register value before the driver touched it, restored
+ * on unload
+ * requested_val - last value the driver set (sysfs or boot parameter),
+ * reapplied on policy reactivation
+ * firmware_captured - whether firmware_val has been read, so a not-yet-seen
+ * CPU isn't mistaken for one whose firmware value is 0
+ */
+struct cppc_saved_state {
+ u64 firmware_val;
+ u64 requested_val;
+ bool firmware_captured;
+};
+
+/*
+ * Per-CPU and not tied to a policy, so the saved values survive policy
+ * teardown/bring-up across CPU hotplug. cpu_data->perf_ctrls is per-policy
+ * and freed on policy ->exit.
+ */
+static DEFINE_PER_CPU(struct cppc_saved_state[CPPC_NR_SAVED_REGS], cppc_saved_state);
+
+static void cppc_cache_perf_ctrls(struct cppc_cpudata *cpu_data,
+ enum cppc_saved_reg_id reg, u64 val)
+{
+ switch (reg) {
+ case CPPC_SAVED_AUTO_SEL:
+ cpu_data->perf_ctrls.auto_sel = val;
+ break;
+ case CPPC_SAVED_EPP:
+ cpu_data->perf_ctrls.energy_perf = val;
+ break;
+ default:
+ break;
+ }
+}
+
+/*
+ * Save the requested value for the given register and CPU, to be reapplied when
+ * the policy is reactivated after CPU hotplug. Also update the per-policy
+ * perf_ctrls copy so the saved and current values stay in sync.
+ */
+static void cppc_save_requested(struct cppc_cpudata *cpu_data, unsigned int cpu,
+ enum cppc_saved_reg_id reg, u64 val)
+{
+ per_cpu(cppc_saved_state, cpu)[reg].requested_val = val;
+ cppc_cache_perf_ctrls(cpu_data, reg, val);
+}
+
+/*
+ * Reapply each register's last requested value from ->init(), so a value set
+ * via sysfs or the boot parameter survives a policy teardown and bring-up
+ * across CPU hotplug. Also keep perf_ctrls in sync with it.
+ */
+static void cppc_cpufreq_reapply_requested_regs(struct cpufreq_policy *policy)
+{
+ struct cppc_cpudata *cpu_data = policy->driver_data;
+ unsigned int cpu, i;
+ u64 val;
+
+ for_each_cpu(cpu, policy->cpus) {
+ for (i = 0; i < CPPC_NR_SAVED_REGS; i++) {
+ val = per_cpu(cppc_saved_state, cpu)[i].requested_val;
+ if (val == U64_MAX)
+ continue;
+
+ cppc_saved_regs[i].set(cpu, val);
+
+ /* Keep perf_ctrls in sync via the policy's CPU. */
+ if (cpu == policy->cpu)
+ cppc_cache_perf_ctrls(cpu_data, i, val);
+ }
+ }
+}
+
+/*
+ * On a CPU's first ->init(), capture each register's firmware value to be
+ * restored on driver unload. Later calls for the same CPU are a no-op. Capturing
+ * from ->init() rather than module load covers CPUs that appear later. Also seed
+ * requested_val to U64_MAX so its zeroed default is not taken as a request for 0.
+ */
+static void cppc_cpufreq_save_firmware_regs(struct cpufreq_policy *policy)
+{
+ unsigned int cpu, i;
+ u64 val;
+
+ for_each_cpu(cpu, policy->cpus) {
+ for (i = 0; i < CPPC_NR_SAVED_REGS; i++) {
+ struct cppc_saved_state *s =
+ &per_cpu(cppc_saved_state, cpu)[i];
+
+ /* Capture once per CPU; skip if already recorded. */
+ if (s->firmware_captured)
+ continue;
+
+ if (cppc_saved_regs[i].get(cpu, &val))
+ val = U64_MAX;
+ s->firmware_val = val;
+ s->requested_val = U64_MAX;
+ s->firmware_captured = true;
+ }
+ }
+}
+
+/* On driver unload, restore each captured CPU's firmware value. */
+static void cppc_cpufreq_restore_firmware_regs(void)
+{
+ unsigned int cpu, i;
+
+ for_each_present_cpu(cpu) {
+ for (i = 0; i < CPPC_NR_SAVED_REGS; i++) {
+ struct cppc_saved_state *s =
+ &per_cpu(cppc_saved_state, cpu)[i];
+
+ if (s->firmware_captured && s->firmware_val != U64_MAX)
+ cppc_saved_regs[i].set(cpu, s->firmware_val);
+ }
+ }
+}
+
/* Autonomous Selection boot parameter modes */
enum {
AUTO_SEL_DISABLED = 0,
@@ -766,6 +934,9 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
policy->cur = cppc_perf_to_khz(caps, caps->highest_perf);
cpu_data->perf_ctrls.desired_perf = caps->highest_perf;
+ /* Capture a CPU's firmware values on its first init, before any driver write. */
+ cppc_cpufreq_save_firmware_regs(policy);
+
/*
* Enable autonomous mode on first init if boot param is set.
* Check last_governor to detect first init and skip if auto_sel
@@ -812,7 +983,7 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
if (ret && ret != -EOPNOTSUPP)
pr_warn("Failed to set EPP for CPU%d (%d)\n", cpu, ret);
else if (!ret)
- cpu_data->perf_ctrls.energy_perf = epp;
+ cppc_save_requested(cpu_data, cpu, CPPC_SAVED_EPP, epp);
}
/* Program min/max/desired into CPPC regs (non-fatal on failure). */
@@ -826,7 +997,7 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
pr_warn("auto_sel CPU%d failed (%d); using OS mode\n",
cpu, ret);
else if (!ret)
- cpu_data->perf_ctrls.auto_sel = true;
+ cppc_save_requested(cpu_data, cpu, CPPC_SAVED_AUTO_SEL, true);
}
if (cpu_data->perf_ctrls.auto_sel) {
@@ -850,6 +1021,10 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
}
cppc_cpufreq_cpu_fie_init(policy);
+
+ /* Reapply any saved values lost across a full policy teardown. */
+ cppc_cpufreq_reapply_requested_regs(policy);
+
return 0;
out:
@@ -1039,6 +1214,8 @@ static ssize_t store_auto_select(struct cpufreq_policy *policy,
}
}
+ cppc_save_requested(cpu_data, policy->cpu, CPPC_SAVED_AUTO_SEL, val);
+
return count;
}
@@ -1111,7 +1288,7 @@ store_energy_performance_preference_val(struct cpufreq_policy *policy,
if (ret)
return ret;
- cpu_data->perf_ctrls.energy_perf = val;
+ cppc_save_requested(cpu_data, policy->cpu, CPPC_SAVED_EPP, val);
return count;
}
@@ -1193,6 +1370,9 @@ static ssize_t store_ospm_nominal_freq(struct cpufreq_policy *policy,
}
}
+ for_each_cpu(sib, policy->cpus)
+ cppc_save_requested(cpu_data, sib, CPPC_SAVED_OSPM_NOMINAL_PERF, perf);
+
return count;
rollback:
@@ -1258,13 +1438,11 @@ static int __init cppc_cpufreq_init(void)
static void __exit cppc_cpufreq_exit(void)
{
- unsigned int cpu;
-
- for_each_present_cpu(cpu)
- cppc_set_auto_sel(cpu, false);
-
cpufreq_unregister_driver(&cppc_cpufreq_driver);
cppc_freq_invariance_exit();
+
+ /* Restore auto_sel and the other saved registers to their firmware value. */
+ cppc_cpufreq_restore_firmware_regs();
}
module_param_cb(auto_sel_mode, &auto_sel_mode_ops, &auto_sel_mode, 0444);
--
2.34.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] cpufreq: CPPC: Preserve OSPM-set registers across hotplug and unload
2026-06-23 9:54 [PATCH] cpufreq: CPPC: Preserve OSPM-set registers across hotplug and unload Sumit Gupta
@ 2026-06-23 11:00 ` Rafael J. Wysocki
0 siblings, 0 replies; 2+ messages in thread
From: Rafael J. Wysocki @ 2026-06-23 11:00 UTC (permalink / raw)
To: Sumit Gupta
Cc: rafael, viresh.kumar, pierre.gondois, ionela.voinescu,
zhenglifeng1, zhanjie9, linux-kernel, linux-pm, linux-tegra,
treding, jonathanh, vsethi, ksitaraman, sanjayc, mochs, bbasu
On Tue, Jun 23, 2026 at 11:54 AM Sumit Gupta <sumitg@nvidia.com> wrote:
>
> Values written to OSPM-set CPPC registers (via sysfs or the autonomous
> boot parameter) can be lost in two ways:
>
> - Across CPU hotplug: the platform may reset a CPU's registers when it
> is offlined.
> - On driver unload: the value the driver wrote is left in the register
> instead of returning to its pre-driver state.
>
> Add a small table-driven mechanism that handles both:
>
> - Capture each register's firmware value when a CPU is first seen and
> restore it on driver unload.
> - Record the last value the driver set and reapply it from ->init()
> when the policy is reactivated after CPU hotplug.
I'm not sure if this is a good idea TBH.
The overall system state when the CPU goes online may be completely
different from the system state when the CPU was online last time, so
there is no reason to restore its settings from before offline, at
least in principle.
> The firmware value is captured on a CPU's first activation rather than
> once at module load, so CPUs offline at boot or hot-added later are
> covered.
>
> Reapply is only needed on a full policy teardown and bring-up, which goes
> through ->init(). In a SHARED_TYPE_ANY policy, offlining a single CPU
> leaves the shared register untouched, so nothing is lost there.
>
> Cover the OSPM Nominal Performance, Autonomous Selection
> (auto_sel) and Energy Performance Preference (EPP) registers. For
> auto_sel it replaces the previous unconditional
> cppc_set_auto_sel(cpu, false) on unload with a restore of the firmware
> value captured at the CPU's first init.
>
> Suggested-by: Pierre Gondois <pierre.gondois@arm.com>
> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
> ---
>
> This applies on top of (not yet merged):
> [1] ACPI: CPPC: Add ospm_nominal_perf support
> https://lore.kernel.org/lkml/20260615185934.2383514-1-sumitg@nvidia.com/
> [2] cpufreq: CPPC: add autonomous mode boot parameter support
> https://lore.kernel.org/lkml/20260623080652.3353386-1-sumitg@nvidia.com/
>
> drivers/cpufreq/cppc_cpufreq.c | 194 +++++++++++++++++++++++++++++++--
> 1 file changed, 186 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index a3fabfb07fbe..d6ea2cbde187 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -28,6 +28,174 @@
>
> static struct cpufreq_driver cppc_cpufreq_driver;
>
> +/*
> + * OSPM-set CPPC registers tracked for save/restore. A value set via sysfs or
> + * the autonomous boot parameter is reapplied across CPU hotplug, and the
> + * firmware value is restored on driver unload.
> + */
> +enum cppc_saved_reg_id {
> + CPPC_SAVED_OSPM_NOMINAL_PERF,
> + CPPC_SAVED_AUTO_SEL,
> + CPPC_SAVED_EPP,
> + CPPC_NR_SAVED_REGS,
> +};
> +
> +struct cppc_saved_reg {
> + int (*get)(int cpu, u64 *val);
> + int (*set)(int cpu, u64 val);
> +};
> +
> +/* u64 wrappers so the bool auto_sel register fits the table signatures. */
> +static int cppc_get_auto_sel_u64(int cpu, u64 *val)
> +{
> + bool enable;
> + int ret;
> +
> + ret = cppc_get_auto_sel(cpu, &enable);
> + if (ret)
> + return ret;
> +
> + *val = enable;
> + return 0;
> +}
> +
> +static int cppc_set_auto_sel_u64(int cpu, u64 val)
> +{
> + return cppc_set_auto_sel(cpu, !!val);
> +}
> +
> +static const struct cppc_saved_reg cppc_saved_regs[CPPC_NR_SAVED_REGS] = {
> + [CPPC_SAVED_OSPM_NOMINAL_PERF] = {
> + cppc_get_ospm_nominal_perf, cppc_set_ospm_nominal_perf,
> + },
> + [CPPC_SAVED_AUTO_SEL] = {
> + cppc_get_auto_sel_u64, cppc_set_auto_sel_u64,
> + },
> + [CPPC_SAVED_EPP] = {
> + cppc_get_epp_perf, cppc_set_epp,
> + },
> +};
> +
> +/*
> + * Per-CPU saved state for each register in cppc_saved_regs[]:
> + * firmware_val - register value before the driver touched it, restored
> + * on unload
> + * requested_val - last value the driver set (sysfs or boot parameter),
> + * reapplied on policy reactivation
> + * firmware_captured - whether firmware_val has been read, so a not-yet-seen
> + * CPU isn't mistaken for one whose firmware value is 0
> + */
> +struct cppc_saved_state {
> + u64 firmware_val;
> + u64 requested_val;
> + bool firmware_captured;
> +};
> +
> +/*
> + * Per-CPU and not tied to a policy, so the saved values survive policy
> + * teardown/bring-up across CPU hotplug. cpu_data->perf_ctrls is per-policy
> + * and freed on policy ->exit.
> + */
> +static DEFINE_PER_CPU(struct cppc_saved_state[CPPC_NR_SAVED_REGS], cppc_saved_state);
> +
> +static void cppc_cache_perf_ctrls(struct cppc_cpudata *cpu_data,
> + enum cppc_saved_reg_id reg, u64 val)
> +{
> + switch (reg) {
> + case CPPC_SAVED_AUTO_SEL:
> + cpu_data->perf_ctrls.auto_sel = val;
> + break;
> + case CPPC_SAVED_EPP:
> + cpu_data->perf_ctrls.energy_perf = val;
> + break;
> + default:
> + break;
> + }
> +}
> +
> +/*
> + * Save the requested value for the given register and CPU, to be reapplied when
> + * the policy is reactivated after CPU hotplug. Also update the per-policy
> + * perf_ctrls copy so the saved and current values stay in sync.
> + */
> +static void cppc_save_requested(struct cppc_cpudata *cpu_data, unsigned int cpu,
> + enum cppc_saved_reg_id reg, u64 val)
> +{
> + per_cpu(cppc_saved_state, cpu)[reg].requested_val = val;
> + cppc_cache_perf_ctrls(cpu_data, reg, val);
> +}
> +
> +/*
> + * Reapply each register's last requested value from ->init(), so a value set
> + * via sysfs or the boot parameter survives a policy teardown and bring-up
> + * across CPU hotplug. Also keep perf_ctrls in sync with it.
> + */
> +static void cppc_cpufreq_reapply_requested_regs(struct cpufreq_policy *policy)
> +{
> + struct cppc_cpudata *cpu_data = policy->driver_data;
> + unsigned int cpu, i;
> + u64 val;
> +
> + for_each_cpu(cpu, policy->cpus) {
> + for (i = 0; i < CPPC_NR_SAVED_REGS; i++) {
> + val = per_cpu(cppc_saved_state, cpu)[i].requested_val;
> + if (val == U64_MAX)
> + continue;
> +
> + cppc_saved_regs[i].set(cpu, val);
> +
> + /* Keep perf_ctrls in sync via the policy's CPU. */
> + if (cpu == policy->cpu)
> + cppc_cache_perf_ctrls(cpu_data, i, val);
> + }
> + }
> +}
> +
> +/*
> + * On a CPU's first ->init(), capture each register's firmware value to be
> + * restored on driver unload. Later calls for the same CPU are a no-op. Capturing
> + * from ->init() rather than module load covers CPUs that appear later. Also seed
> + * requested_val to U64_MAX so its zeroed default is not taken as a request for 0.
> + */
> +static void cppc_cpufreq_save_firmware_regs(struct cpufreq_policy *policy)
> +{
> + unsigned int cpu, i;
> + u64 val;
> +
> + for_each_cpu(cpu, policy->cpus) {
> + for (i = 0; i < CPPC_NR_SAVED_REGS; i++) {
> + struct cppc_saved_state *s =
> + &per_cpu(cppc_saved_state, cpu)[i];
> +
> + /* Capture once per CPU; skip if already recorded. */
> + if (s->firmware_captured)
> + continue;
> +
> + if (cppc_saved_regs[i].get(cpu, &val))
> + val = U64_MAX;
> + s->firmware_val = val;
> + s->requested_val = U64_MAX;
> + s->firmware_captured = true;
> + }
> + }
> +}
> +
> +/* On driver unload, restore each captured CPU's firmware value. */
> +static void cppc_cpufreq_restore_firmware_regs(void)
> +{
> + unsigned int cpu, i;
> +
> + for_each_present_cpu(cpu) {
> + for (i = 0; i < CPPC_NR_SAVED_REGS; i++) {
> + struct cppc_saved_state *s =
> + &per_cpu(cppc_saved_state, cpu)[i];
> +
> + if (s->firmware_captured && s->firmware_val != U64_MAX)
> + cppc_saved_regs[i].set(cpu, s->firmware_val);
> + }
> + }
> +}
> +
> /* Autonomous Selection boot parameter modes */
> enum {
> AUTO_SEL_DISABLED = 0,
> @@ -766,6 +934,9 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
> policy->cur = cppc_perf_to_khz(caps, caps->highest_perf);
> cpu_data->perf_ctrls.desired_perf = caps->highest_perf;
>
> + /* Capture a CPU's firmware values on its first init, before any driver write. */
> + cppc_cpufreq_save_firmware_regs(policy);
> +
> /*
> * Enable autonomous mode on first init if boot param is set.
> * Check last_governor to detect first init and skip if auto_sel
> @@ -812,7 +983,7 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
> if (ret && ret != -EOPNOTSUPP)
> pr_warn("Failed to set EPP for CPU%d (%d)\n", cpu, ret);
> else if (!ret)
> - cpu_data->perf_ctrls.energy_perf = epp;
> + cppc_save_requested(cpu_data, cpu, CPPC_SAVED_EPP, epp);
> }
>
> /* Program min/max/desired into CPPC regs (non-fatal on failure). */
> @@ -826,7 +997,7 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
> pr_warn("auto_sel CPU%d failed (%d); using OS mode\n",
> cpu, ret);
> else if (!ret)
> - cpu_data->perf_ctrls.auto_sel = true;
> + cppc_save_requested(cpu_data, cpu, CPPC_SAVED_AUTO_SEL, true);
> }
>
> if (cpu_data->perf_ctrls.auto_sel) {
> @@ -850,6 +1021,10 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
> }
>
> cppc_cpufreq_cpu_fie_init(policy);
> +
> + /* Reapply any saved values lost across a full policy teardown. */
> + cppc_cpufreq_reapply_requested_regs(policy);
> +
> return 0;
>
> out:
> @@ -1039,6 +1214,8 @@ static ssize_t store_auto_select(struct cpufreq_policy *policy,
> }
> }
>
> + cppc_save_requested(cpu_data, policy->cpu, CPPC_SAVED_AUTO_SEL, val);
> +
> return count;
> }
>
> @@ -1111,7 +1288,7 @@ store_energy_performance_preference_val(struct cpufreq_policy *policy,
> if (ret)
> return ret;
>
> - cpu_data->perf_ctrls.energy_perf = val;
> + cppc_save_requested(cpu_data, policy->cpu, CPPC_SAVED_EPP, val);
>
> return count;
> }
> @@ -1193,6 +1370,9 @@ static ssize_t store_ospm_nominal_freq(struct cpufreq_policy *policy,
> }
> }
>
> + for_each_cpu(sib, policy->cpus)
> + cppc_save_requested(cpu_data, sib, CPPC_SAVED_OSPM_NOMINAL_PERF, perf);
> +
> return count;
>
> rollback:
> @@ -1258,13 +1438,11 @@ static int __init cppc_cpufreq_init(void)
>
> static void __exit cppc_cpufreq_exit(void)
> {
> - unsigned int cpu;
> -
> - for_each_present_cpu(cpu)
> - cppc_set_auto_sel(cpu, false);
> -
> cpufreq_unregister_driver(&cppc_cpufreq_driver);
> cppc_freq_invariance_exit();
> +
> + /* Restore auto_sel and the other saved registers to their firmware value. */
> + cppc_cpufreq_restore_firmware_regs();
> }
>
> module_param_cb(auto_sel_mode, &auto_sel_mode_ops, &auto_sel_mode, 0444);
> --
> 2.34.1
>
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-06-23 11:01 UTC | newest]
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2026-06-23 9:54 [PATCH] cpufreq: CPPC: Preserve OSPM-set registers across hotplug and unload Sumit Gupta
2026-06-23 11:00 ` Rafael J. Wysocki
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