[Nouveau] [PATCH] drm/nouveau: don't touch has_pr3 for likely-non-NVIDIA device

[Ratchanan Srirattanamet <peathot@hotmail.com>]

The call site of nouveau_dsm_pci_probe() uses single set of output
variables for all invocations. So, we must not write anything to them
until we think this is an NVIDIA device of interest. Otherwise, if we
are called with another device after the NVIDIA device, we'll clober the
result of the NVIDIA device.

In this case, if the other device doesn't have _PR3 resources, the
detection later would miss the presence of power resource support, and
the rest of the code will keep using Optimus DSM, breaking power
management for that machine. In particular, this fixes power management
of the NVIDIA card in Lenovo Legion 5-15ARH05... well, at least
partially. New error shows up, but this patch is correct in itself
anyway.

As a bonus, we'll also stop preventing _PR3 usage from the bridge for
unrelated devices, which is always nice, I guess.

As noted in commit ccfc2d5cdb024 ("drm/nouveau: Use generic helper to
check _PR3 presence"), care is taken to leave the _PR3 detection outside
of the optimus_func condition.

https://gitlab.freedesktop.org/drm/nouveau/-/issues/79

Fixes: ccfc2d5cdb024 ("drm/nouveau: Use generic helper to check _PR3
presence")
Signed-off-by: Ratchanan Srirattanamet <peathot@hotmail.com>
---

Hello,

This is my first time submitting a Linux patch. I've done a
number of PR/MR workflows on GitHub or GitLab, but never done any
email-oriented development. So, please excuse me if I'm doing something
incorrectly.

 drivers/gpu/drm/nouveau/nouveau_acpi.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_acpi.c b/drivers/gpu/drm/nouveau/nouveau_acpi.c
index 7c15f6448428..c88bda3ac820 100644
--- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
+++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
@@ -220,15 +220,6 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
 	int optimus_funcs;
 	struct pci_dev *parent_pdev;
 
-	*has_pr3 = false;
-	parent_pdev = pci_upstream_bridge(pdev);
-	if (parent_pdev) {
-		if (parent_pdev->bridge_d3)
-			*has_pr3 = pci_pr3_present(parent_pdev);
-		else
-			pci_d3cold_disable(pdev);
-	}
-
 	dhandle = ACPI_HANDLE(&pdev->dev);
 	if (!dhandle)
 		return;
@@ -249,6 +240,15 @@ static void nouveau_dsm_pci_probe(struct pci_dev *pdev, acpi_handle *dhandle_out
 	*has_opt = !!optimus_funcs;
 	*has_opt_flags = optimus_funcs & (1 << NOUVEAU_DSM_OPTIMUS_FLAGS);
 
+	*has_pr3 = false;
+	parent_pdev = pci_upstream_bridge(pdev);
+	if (parent_pdev) {
+		if (parent_pdev->bridge_d3)
+			*has_pr3 = pci_pr3_present(parent_pdev);
+		else
+			pci_d3cold_disable(pdev);
+	}
+
 	if (optimus_funcs) {
 		uint32_t result;
 		nouveau_optimus_dsm(dhandle, NOUVEAU_DSM_OPTIMUS_CAPS, 0,
-- 
2.25.1

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