[PATCH i-g-t v2 5/7] lib/igt_pm: Add power/wakeup_active_count accessor

[Pranay Samala <pranay.samala@intel.com>]

Add igt_pm_get_wakeup_active_count(), which reads how many times the
device's wakeup source has been activated.

wakeup_source_activate() bumps this unconditionally, so it counts runtime
resumes too, on both the PCIe (pci_pme_wakeup()) and ACPI GPE
(pci_acpi_wake_dev()) delivery routes. An increment across a suspended
window therefore means the device signalled the resume itself, i.e. a PME
arrived, rather than the host waking it.

Neither alternative works: power/wakeup_count only moves under
events_check_enabled, which the PM core sets for system suspend and
hibernate, and PME_Status is cleared by the PCI/PM core as it handles the
wakeup, so it cannot be sampled afterwards.

Parsing uses a checked sscanf() rather than an asserted one, since the
counter reads back as a bare newline when the device has no wakeup source,
that is when power/wakeup is disabled. That has to give 0, not a failure.

Assisted-by: GitHub_Copilot:claude-opus-5
Signed-off-by: Pranay Samala <pranay.samala@intel.com>
---
 lib/igt_pm.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_pm.h |  1 +
 2 files changed, 49 insertions(+)

diff --git a/lib/igt_pm.c b/lib/igt_pm.c
index b8b66e120..4ed80b27a 100644
--- a/lib/igt_pm.c
+++ b/lib/igt_pm.c
@@ -1498,6 +1498,34 @@ int igt_pm_get_runtime_usage(struct pci_device *pci_dev)
 	return usage;
 }
 
+/*
+ * Read an unsigned power attribute of @pci_dev, returning 0 if the attribute
+ * does not exist or does not hold a number.
+ *
+ * The latter is not hypothetical: the wakeup counters exist for every wakeup
+ * capable device, but the PM core emits a bare newline for them while the
+ * device has no wakeup source, i.e. while power/wakeup is disabled.
+ */
+static uint64_t igt_pm_read_power_attr_u64(struct pci_device *pci_dev,
+					   const char *attr)
+{
+	char buf[64];
+	uint64_t val;
+	int fd;
+
+	fd = __igt_pm_get_power_attr_fd(pci_dev, attr, O_RDONLY);
+	if (fd < 0)
+		return 0;
+
+	if (!igt_pm_read_power_attr(fd, buf, sizeof(buf), false) ||
+	    sscanf(buf, "%" SCNu64, &val) != 1)
+		val = 0;
+
+	close(fd);
+
+	return val;
+}
+
 #define IGT_PM_WAKEUP_ENABLED_STR "enabled\n"
 #define IGT_PM_WAKEUP_DISABLED_STR "disabled\n"
 
@@ -1631,6 +1659,26 @@ void igt_pm_restore_wakeup(void)
 	__igt_pm_wakeup.pci_dev = NULL;
 }
 
+/**
+ * igt_pm_get_wakeup_active_count:
+ * @pci_dev: PCI device struct
+ *
+ * Reads power/wakeup_active_count, the number of times the device's wakeup
+ * source was activated. An increment across a runtime suspended window means
+ * the resume was signalled by the device, i.e. a PME arrived, rather than
+ * initiated by something host side such as HPD polling.
+ *
+ * Use this and not power/wakeup_count, which is only incremented under
+ * events_check_enabled and so never moves for a runtime resume.
+ *
+ * Return: the wakeup active count, or 0 if the device is not wakeup capable or
+ * has power/wakeup disabled.
+ */
+uint64_t igt_pm_get_wakeup_active_count(struct pci_device *pci_dev)
+{
+	return igt_pm_read_power_attr_u64(pci_dev, "wakeup_active_count");
+}
+
 /**
  * igt_pm_ignore_slpc_efficient_freq:
  * @i915: open i915 drm file descriptor
diff --git a/lib/igt_pm.h b/lib/igt_pm.h
index d15b01ec9..1e9234154 100644
--- a/lib/igt_pm.h
+++ b/lib/igt_pm.h
@@ -106,6 +106,7 @@ int igt_pm_get_runtime_usage(struct pci_device *pci_dev);
 bool igt_pm_has_wakeup_support(struct pci_device *pci_dev);
 void igt_pm_set_wakeup_enabled(struct pci_device *pci_dev, bool enable);
 void igt_pm_restore_wakeup(void);
+uint64_t igt_pm_get_wakeup_active_count(struct pci_device *pci_dev);
 void igt_pm_ignore_slpc_efficient_freq(int i915, int gtfd, bool val);
 bool igt_has_pci_pm_capability(struct pci_device *pci_dev);
 bool igt_pm_pci_pme_supported(struct pci_device *pci_dev,
-- 
2.53.0