[PATCH v3 4/4] drivers/perf: Fix the condition where the root port is runtime suspended

[Yicong Yang]

The PMU is based on the corresponding root port's VSEC capability,
which could be inaccessible if the target root port is runtime
suspended to D3Cold. Fix this by getting/putting the root port's
runtime pm when the event of this PMU is init/destroy. It cannot
be done in the add()/del() callbacks where the events is actually
scheduled, since there's not way to runtime resume the device
synchronously in the atomic context (add()/del()).

With this patch, the root port will keep D0 while counting and suspend
after counting finished (for prove the correctness since my board does
not support D3Cold):
  root@localhost:~# cat /sys/bus/pci/devices/0008\:00\:00.0/power_state
  D3hot
  root@localhost:~# perf stat -e dwc_rootport_8000/one_cycle/ &
  [1] 14580
  root@localhost:~# cat /sys/bus/pci/devices/0008\:00\:00.0/power_state
  D0
  root@localhost:~# kill %1
  [1]+  Terminated              perf stat -e dwc_rootport_8000/one_cycle/
  root@localhost:~# cat /sys/bus/pci/devices/0008\:00\:00.0/power_state
  D3hot

The root port also needs to be runtime resumed during PCIe PMU
device registration and probe, so get/put the runtime pm there
as well.

Fixes: af9597adc2f1 ("drivers/perf: add DesignWare PCIe PMU driver")
Closes: https://lore.kernel.org/linux-pci/20260629094234.F25E71F000E9@xxxxxxxxxxxxxxx/
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Signed-off-by: Yicong Yang <yang.yicong@xxxxxxxxxxxxx>
---
 drivers/perf/dwc_pcie_pmu.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/perf/dwc_pcie_pmu.c b/drivers/perf/dwc_pcie_pmu.c
index 7b4ee71b966b..aea387d0d0fe 100644
--- a/drivers/perf/dwc_pcie_pmu.c
+++ b/drivers/perf/dwc_pcie_pmu.c
@@ -17,6 +17,7 @@
 #include <linux/list.h>
 #include <linux/pcie-dwc.h>
 #include <linux/perf_event.h>
+#include <linux/pm_runtime.h>
 #include <linux/pci.h>
 #include <linux/smp.h>
 #include <linux/sysfs.h>
@@ -474,12 +475,20 @@ static enum hrtimer_restart dwc_pcie_pmu_hrtimer_callback(struct hrtimer *hrtime
 	return HRTIMER_RESTART;
 }
 
+static void dwc_pcie_pmu_event_destroy(struct perf_event *event)
+{
+	struct dwc_pcie_pmu *pcie_pmu = to_dwc_pcie_pmu(event->pmu);
+
+	pm_runtime_put_autosuspend(&pcie_pmu->pdev->dev);
+}
+
 static int dwc_pcie_pmu_event_init(struct perf_event *event)
 {
 	struct dwc_pcie_pmu *pcie_pmu = to_dwc_pcie_pmu(event->pmu);
 	enum dwc_pcie_event_type type = DWC_PCIE_EVENT_TYPE(event);
 	struct perf_event *sibling;
 	u32 lane;
+	int ret;
 
 	if (event->attr.type != event->pmu->type)
 		return -ENOENT;
@@ -509,7 +518,16 @@ static int dwc_pcie_pmu_event_init(struct perf_event *event)
 	if (dwc_pcie_pmu_validate_group(event))
 		return -ENOSPC;
 
+	/*
+	 * Resume the root port for VSEC access. Use RPM_TRANSPARENT as the
+	 * VSEC is accessible if root port's runtime pm is disabled.
+	 */
+	ret = pm_runtime_get_active(&pcie_pmu->pdev->dev, RPM_TRANSPARENT);
+	if (ret < 0)
+		return ret;
+
 	event->cpu = pcie_pmu->on_cpu;
+	event->destroy = dwc_pcie_pmu_event_destroy;
 
 	return 0;
 }
@@ -776,6 +794,7 @@ static int dwc_pcie_pmu_probe(struct faux_device *fdev)
 	if (!name)
 		return -ENOMEM;
 
+	guard(pm_runtime_active_auto)(&pdev->dev);
 	vsec = dwc_pcie_des_cap(pdev);
 	if (!vsec)
 		return -ENODEV;
@@ -909,6 +928,8 @@ static int __init dwc_pcie_pmu_init(void)
 	dwc_pcie_pmu_hp_state = ret;
 
 	for_each_pci_dev(pdev) {
+		guard(pm_runtime_active_auto)(&pdev->dev);
+
 		if (!dwc_pcie_des_cap(pdev))
 			continue;
 
-- 
2.50.1 (Apple Git-155)