platform/x86:intel/pmc: Enable the ACPI PM Timer to be turned off when suspended

Allow to disable ACPI PM Timer on suspend and enable on resume. A
disabled timer helps optimise power consumption when the system is
suspended. On resume the timer is only reactivated if it was activated
prior to suspend, so unless the ACPI PM timer is enabled in the BIOS,
this won't change anything.

The ACPI PM timer is used by Intel's iTCO/wdat_wdt watchdog to drive the
watchdog, so it doesn't need to run during suspend.

Signed-off-by: Marek Maslanka <mmaslanka@google.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20240812184208.1080710-1-mmaslanka@google.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/platform/x86/intel/pmc/core.c b/drivers/platform/x86/intel/pmc/core.c
index 01ae71c6df59..c91c753b120e 100644
--- a/drivers/platform/x86/intel/pmc/core.c
+++ b/drivers/platform/x86/intel/pmc/core.c
@@ -11,6 +11,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/acpi_pmtmr.h>
 #include <linux/bitfield.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
@@ -1208,6 +1209,38 @@ static bool pmc_core_is_pson_residency_enabled(struct pmc_dev *pmcdev)
 	return val == 1;
 }
 
+/**
+ * Enable or disable ACPI PM Timer
+ *
+ * This function is intended to be a callback for ACPI PM suspend/resume event.
+ * The ACPI PM Timer is enabled on resume only if it was enabled during suspend.
+ */
+static void pmc_core_acpi_pm_timer_suspend_resume(void *data, bool suspend)
+{
+	struct pmc_dev *pmcdev = data;
+	struct pmc *pmc = pmcdev->pmcs[PMC_IDX_MAIN];
+	const struct pmc_reg_map *map = pmc->map;
+	bool enabled;
+	u32 reg;
+
+	if (!map->acpi_pm_tmr_ctl_offset)
+		return;
+
+	guard(mutex)(&pmcdev->lock);
+
+	if (!suspend && !pmcdev->enable_acpi_pm_timer_on_resume)
+		return;
+
+	reg = pmc_core_reg_read(pmc, map->acpi_pm_tmr_ctl_offset);
+	enabled = !(reg & map->acpi_pm_tmr_disable_bit);
+	if (suspend)
+		reg |= map->acpi_pm_tmr_disable_bit;
+	else
+		reg &= ~map->acpi_pm_tmr_disable_bit;
+	pmc_core_reg_write(pmc, map->acpi_pm_tmr_ctl_offset, reg);
+
+	pmcdev->enable_acpi_pm_timer_on_resume = suspend && enabled;
+}
 
 static void pmc_core_dbgfs_unregister(struct pmc_dev *pmcdev)
 {
@@ -1404,6 +1437,7 @@ static int pmc_core_probe(struct platform_device *pdev)
 	struct pmc_dev *pmcdev;
 	const struct x86_cpu_id *cpu_id;
 	int (*core_init)(struct pmc_dev *pmcdev);
+	const struct pmc_reg_map *map;
 	struct pmc *primary_pmc;
 	int ret;
 
@@ -1462,6 +1496,11 @@ static int pmc_core_probe(struct platform_device *pdev)
 	pm_report_max_hw_sleep(FIELD_MAX(SLP_S0_RES_COUNTER_MASK) *
 			       pmc_core_adjust_slp_s0_step(primary_pmc, 1));
 
+	map = primary_pmc->map;
+	if (map->acpi_pm_tmr_ctl_offset)
+		acpi_pmtmr_register_suspend_resume_callback(pmc_core_acpi_pm_timer_suspend_resume,
+							 pmcdev);
+
 	device_initialized = true;
 	dev_info(&pdev->dev, " initialized\n");
 
@@ -1471,6 +1510,12 @@ static int pmc_core_probe(struct platform_device *pdev)
 static void pmc_core_remove(struct platform_device *pdev)
 {
 	struct pmc_dev *pmcdev = platform_get_drvdata(pdev);
+	const struct pmc *pmc = pmcdev->pmcs[PMC_IDX_MAIN];
+	const struct pmc_reg_map *map = pmc->map;
+
+	if (map->acpi_pm_tmr_ctl_offset)
+		acpi_pmtmr_unregister_suspend_resume_callback();
+
 	pmc_core_dbgfs_unregister(pmcdev);
 	pmc_core_clean_structure(pdev);
 }