[Intel-xe] [PATCH v2] drm/xe/pm: fix unbalanced ref handling

[Lucas De Marchi]

On Wed, Feb 22, 2023 at 12:18:45PM +0000, Matthew Auld wrote:
>In local_pci_probe() the core kernel increments the rpm for the device,
>just before calling into the probe hook. If the driver/device supports
>runtime pm it is then meant to put this ref during probe (like we do in
>xe_pm_runtime_init()). However when removing the device we then also
>need to take the reference back, otherwise the ref that is put in
>pci_device_remove() will be unbalanced when for example unloading the
>driver, leading to warnings like:
>
>    [ 3808.596345] xe 0000:03:00.0: Runtime PM usage count underflow!
>
>Fix this by incrementing the rpm ref when removing the device.
>
>v2:
>  - Improve the terminology in the commit message; s/drop/put/ etc (Lucas & Rodrigo)
>  - Also call pm_runtime_forbid(dev) (Rodrigo)
>
>Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/193
>Signed-off-by: Matthew Auld <matthew.auld at intel.com>
>Cc: Lucas De Marchi <lucas.demarchi at intel.com>
>Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>


Reviewed-by: Lucas De Marchi <lucas.demarchi at intel.com>

Lucas De Marchi

>---
> drivers/gpu/drm/xe/xe_pci.c | 1 +
> drivers/gpu/drm/xe/xe_pm.c  | 8 ++++++++
> drivers/gpu/drm/xe/xe_pm.h  | 1 +
> 3 files changed, 10 insertions(+)
>
>diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
>index 25598de3a1fc..85d337cd8fbe 100644
>--- a/drivers/gpu/drm/xe/xe_pci.c
>+++ b/drivers/gpu/drm/xe/xe_pci.c
>@@ -441,6 +441,7 @@ static void xe_pci_remove(struct pci_dev *pdev)
> 		return;
>
> 	xe_device_remove(xe);
>+	xe_pm_runtime_fini(xe);
> 	pci_set_drvdata(pdev, NULL);
> }
>
>diff --git a/drivers/gpu/drm/xe/xe_pm.c b/drivers/gpu/drm/xe/xe_pm.c
>index 44c38e670587..769f380cf1d4 100644
>--- a/drivers/gpu/drm/xe/xe_pm.c
>+++ b/drivers/gpu/drm/xe/xe_pm.c
>@@ -128,6 +128,14 @@ void xe_pm_runtime_init(struct xe_device *xe)
> 	pm_runtime_put_autosuspend(dev);
> }
>
>+void xe_pm_runtime_fini(struct xe_device *xe)
>+{
>+	struct device *dev = xe->drm.dev;
>+
>+	pm_runtime_get_sync(dev);
>+	pm_runtime_forbid(dev);
>+}
>+
> int xe_pm_runtime_suspend(struct xe_device *xe)
> {
> 	struct xe_gt *gt;
>diff --git a/drivers/gpu/drm/xe/xe_pm.h b/drivers/gpu/drm/xe/xe_pm.h
>index b8c5f9558e26..6a885585f653 100644
>--- a/drivers/gpu/drm/xe/xe_pm.h
>+++ b/drivers/gpu/drm/xe/xe_pm.h
>@@ -14,6 +14,7 @@ int xe_pm_suspend(struct xe_device *xe);
> int xe_pm_resume(struct xe_device *xe);
>
> void xe_pm_runtime_init(struct xe_device *xe);
>+void xe_pm_runtime_fini(struct xe_device *xe);
> int xe_pm_runtime_suspend(struct xe_device *xe);
> int xe_pm_runtime_resume(struct xe_device *xe);
> int xe_pm_runtime_get(struct xe_device *xe);
>-- 
>2.39.1
>