[PATCH] drm/nouveau/acpi: fix check for power resources support

[Peter Wu <peter-VTkQYDcBqhK7DlmcbJSQ7g@public.gmane.org>]

Check whether the kernel really supports power resources for a device,
otherwise the power might not be removed when the device is runtime
suspended (DSM should still work in these cases where PR does not).

Link: https://bugs.freedesktop.org/show_bug.cgi?id=98398
Fixes: 692a17dcc292 ("drm/nouveau/acpi: fix lockup with PCIe runtime PM")
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
---
Hi,

Maybe Cc: stable (4.8+)?

Compile-tested only. Rick, can you test if this patch fixes the problem for you?

This check was actually in the original patch, but it was changed:
https://lists.freedesktop.org/archives/nouveau/2016-May/025125.html
Re-adding the check as suggested by Mika.

Kind regards,
Peter
---
 drivers/gpu/drm/nouveau/nouveau_acpi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
index dc57b62..193573d 100644
--- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
+++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
@@ -240,7 +240,8 @@ static bool nouveau_pr3_present(struct pci_dev *pdev)
 	if (!parent_adev)
 		return false;
 
-	return acpi_has_method(parent_adev->handle, "_PR3");
+	return parent_adev->power.flags.power_resources &&
+		acpi_has_method(parent_adev->handle, "_PR3");
 }
 
 static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out,
-- 
2.10.1

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