Re: Pressing the power button causes the device to freeze completely

["Rafael J. Wysocki" <rafael@kernel.org>]

On Sunday, April 26, 2026 10:45:03 PM CEST Evgeny Sagatov wrote:
> dmesg | grep "frequency s"
> [    8.622778] acpi_cpufreq: CPU0: Using I/O space for frequency scaling
> [    8.622806] cpufreq: CPU0: Fast frequency switching enabled
> [    8.622869] acpi_cpufreq: CPU1: Using I/O space for frequency scaling
> [    8.622888] cpufreq: CPU1: Fast frequency switching enabled
> [    8.622938] acpi_cpufreq: CPU2: Using I/O space for frequency scaling
> [    8.622955] cpufreq: CPU2: Fast frequency switching enabled
> [    8.623006] acpi_cpufreq: CPU3: Using I/O space for frequency scaling
> [    8.623026] cpufreq: CPU3: Fast frequency switching enabled
> 
> When I press the power button, a message is displayed:
> apr 26 23:40:36 srv kernel: ACPI power button event
> 
> The PC does not freeze.

Good.

> The single core performance benchmark shows good values.

That most likely is a coincidence.

The above means that the issue is related to HW accesses in the I/O space.

I don't actually think that the writes to the I/O space outright clash with
each other, but the timing between them may be somewhat overly aggressive.

Let's first check what I/O ports come into play though.

Please apply the patch below (which is a replacement for the previous one),
run

$ dmesg | grep "frequency scaling"

after a fresh boot of the new kernel and let me know the output of it.

Then, press the power button and send the messages printed after that.

---
 drivers/acpi/acpica/evevent.c  |   12 ++++++++++++
 drivers/cpufreq/acpi-cpufreq.c |    8 ++++++--
 drivers/cpufreq/cpufreq.c      |    1 +
 3 files changed, 19 insertions(+), 2 deletions(-)

--- a/drivers/acpi/acpica/evevent.c
+++ b/drivers/acpi/acpica/evevent.c
@@ -243,6 +243,18 @@ static u32 acpi_ev_fixed_event_dispatch(
 	(void)acpi_write_bit_register(acpi_gbl_fixed_event_info[event].
 				      status_register_id, ACPI_CLEAR_STATUS);
 
+	if (event == ACPI_EVENT_POWER_BUTTON) {
+		pr_info("ACPI power button event\n");
+		if (acpi_gbl_fixed_event_info[event].status_register_id == 0)
+			pr_info("ACPI event status I/O port number: %llu\n",
+				acpi_gbl_xpm1a_status.address);
+		else
+			pr_info("ACPI event status register ID: %u\n",
+				acpi_gbl_fixed_event_info[event].status_register_id);
+
+		return (ACPI_INTERRUPT_HANDLED);
+	}
+
 	/*
 	 * Make sure that a handler exists. If not, report an error
 	 * and disable the event to prevent further interrupts.
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -479,8 +479,8 @@ static unsigned int acpi_cpufreq_fast_sw
 			return next_freq;
 	}
 
-	data->cpu_freq_write(&perf->control_register,
-			     perf->states[next_perf_state].control);
+	/*data->cpu_freq_write(&perf->control_register,
+			     perf->states[next_perf_state].control);*/
 	perf->state = next_perf_state;
 	return next_freq;
 }
@@ -887,9 +887,13 @@ static int acpi_cpufreq_cpu_init(struct
 		 * unknown and not detectable via IO ports.
 		 */
 		policy->cur = acpi_cpufreq_guess_freq(data, policy->cpu);
+		pr_info("CPU%u: Using I/O space for frequency scaling\n", cpu);
+		pr_info("CPU%u: frequency scaling I/O port number: %llu\n", cpu,
+			perf->control_register.address);
 		break;
 	case ACPI_ADR_SPACE_FIXED_HARDWARE:
 		acpi_cpufreq_driver.get = get_cur_freq_on_cpu;
+		pr_info("CPU%u: Using FFH for frequency scaling\n", cpu);
 		break;
 	default:
 		break;
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -473,6 +473,7 @@ void cpufreq_enable_fast_switch(struct c
 	if (cpufreq_fast_switch_count >= 0) {
 		cpufreq_fast_switch_count++;
 		policy->fast_switch_enabled = true;
+		pr_info("CPU%u: Fast frequency switching enabled\n", policy->cpu);
 	} else {
 		pr_warn("CPU%u: Fast frequency switching not enabled\n",
 			policy->cpu);