[PATCH] PCI: Only override AMD USB controller if required

From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
To: linux-pci@vger.kernel.org
Cc: bhelgaas@google.com, kernel@gpiccoli.net, kernel-dev@igalia.com,
	"Guilherme G. Piccoli" <gpiccoli@igalia.com>,
	Huang Rui <ray.huang@amd.com>, Vicki Pfau <vi@endrift.com>
Subject: [PATCH] PCI: Only override AMD USB controller if required
Date: Mon, 20 Nov 2023 13:04:36 -0300	[thread overview]
Message-ID: <20231120160531.361552-1-gpiccoli@igalia.com> (raw)

By running a Vangogh device (Steam Deck), the following message
was noticed in the kernel log:

"pci 0000:04:00.3: PCI class overridden (0x0c03fe -> 0x0c03fe) so dwc3 driver can claim this instead of xhci"

Effectively this means the quirk executed but changed nothing, since the
class of this device was already the proper one (likely adjusted by
newer firmware versions).

Hence, let's just check and perform the override only if necessary.

Cc: Huang Rui <ray.huang@amd.com>
Cc: Vicki Pfau <vi@endrift.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
---
 drivers/pci/quirks.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index ea476252280a..4e3bb1643b09 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -702,10 +702,13 @@ static void quirk_amd_dwc_class(struct pci_dev *pdev)
 {
 	u32 class = pdev->class;
 
-	/* Use "USB Device (not host controller)" class */
-	pdev->class = PCI_CLASS_SERIAL_USB_DEVICE;
-	pci_info(pdev, "PCI class overridden (%#08x -> %#08x) so dwc3 driver can claim this instead of xhci\n",
-		 class, pdev->class);
+	if (class != PCI_CLASS_SERIAL_USB_DEVICE) {
+		/* Use "USB Device (not host controller)" class */
+		pdev->class = PCI_CLASS_SERIAL_USB_DEVICE;
+		pci_info(pdev,
+			"PCI class overridden (%#08x -> %#08x) so dwc3 driver can claim this instead of xhci\n",
+			class, pdev->class);
+	}
 }
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_NL_USB,
 		quirk_amd_dwc_class);
-- 
2.42.0

