[PATCH i-g-t v3 5/7] lib/igt_pm: Add power/wakeup_active_count accessor

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

Add igt_pm_get_wakeup_active_count(), the number of times the device's
wakeup source was activated.

Every PCI PME delivery route ends in pci_wakeup_event(), which bumps
this count: the native PCIe PME interrupt, an ACPI GPE, and the PCI
core PME poll (pci_pme_list_scan(), every 1s), which is the likely
route for an integrated GPU without a GPE. An increment across a
suspended window therefore means the device woke itself with a PME,
rather than the host waking it.

power/wakeup_count does not work for this, as it only moves during
system suspend, and neither does PME_Status, which the PCI core clears
while handling the wakeup.

The count is unavailable while power/wakeup is disabled. Since 0 is a
valid count, return -1 then, so callers can tell "no wakeup source"
from "no PME".

v3:
- Mention the PCI core PME poll route, and correct the PCIe route, which
  is pcie_pme_handle_request() rather than pci_pme_wakeup() (Kunal)
- Return int64_t, -1 when there is no wakeup source, instead of 0 (Kunal)

Signed-off-by: Pranay Samala <pranay.samala@intel.com>
---
 lib/igt_pm.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_pm.h |  1 +
 2 files changed, 54 insertions(+)

diff --git a/lib/igt_pm.c b/lib/igt_pm.c
index 1173b2b68..f4d5d5c7b 100644
--- a/lib/igt_pm.c
+++ b/lib/igt_pm.c
@@ -1498,6 +1498,35 @@ int igt_pm_get_runtime_usage(struct pci_device *pci_dev)
 	return usage;
 }
 
+/*
+ * Read an unsigned power attribute of @pci_dev, returning -1 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. Since 0 is
+ * a valid count, that case has to be told apart from it.
+ */
+static int64_t igt_pm_read_power_attr_u64(struct pci_device *pci_dev,
+					  const char *attr)
+{
+	char buf[64];
+	int64_t val;
+	int fd;
+
+	fd = __igt_pm_get_power_attr_fd(pci_dev, attr, O_RDONLY);
+	if (fd < 0)
+		return -1;
+
+	if (!igt_pm_read_power_attr(fd, buf, sizeof(buf), false) ||
+	    sscanf(buf, "%" SCNd64, &val) != 1 || val < 0)
+		val = -1;
+
+	close(fd);
+
+	return val;
+}
+
 #define IGT_PM_WAKEUP_ENABLED_STR "enabled\n"
 #define IGT_PM_WAKEUP_DISABLED_STR "disabled\n"
 
@@ -1638,6 +1667,30 @@ 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.
+ *
+ * The count only exists while the device has a wakeup source, i.e. while
+ * power/wakeup is enabled, and restarts from 0 each time one is created. See
+ * igt_pm_set_wakeup_enabled().
+ *
+ * Return: the wakeup active count, or -1 if the device is not wakeup capable,
+ * has power/wakeup disabled, or the count could not be read.
+ */
+int64_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 c3facbd69..3d857080a 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);
+int64_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