PCI: apple: Avoid PERST# deassertion through gpiod initialization

The Aquantia AQC113 10GB ethernet device used in Apple silicon
Mac Studio, Mac Pro and as option in Mac mini is sensitive to PERST#
deassertion before clock setup. The perst pins are defined as
GPIO_ACTIVE_LOW in the device tree. GPIOD_OUT_LOW will deassert the
PERST# pin. This breaks the link setup reliably under m1n1's hypervisor
on a M1 Ultra Mac Studio. There might have been reports of unavailable
10GB NICs before u-boot took over the PCIe link setup.

Signed-off-by: Janne Grunau <j@jannau.net>
Fixes: a6b9ede ("PCI: apple: Do not leak reset GPIO on unbind/unload/error")
Fixes: 1e33888 ("PCI: apple: Add initial hardware bring-up")

Author: jannau

drivers/pci/controller/pcie-apple.c

@@ -618,8 +618,13 @@ static int apple_pcie_setup_link(struct apple_pcie *pcie,
 	u32 stat;
 	int ret;
 
+	/*
+	 * Leave PERST# as is. The Aquantia AQC113 10GB nic used desktop macs is
+	 * sensitive to deasserting it without prior clock setup.
+	 * Observed on M1 Max/Ultra Mac Studios under m1n1's hypervisor.
+	 */
 	reset = devm_fwnode_gpiod_get(pcie->dev, of_fwnode_handle(np), "reset",
-				      GPIOD_OUT_LOW, "PERST#");
+				      GPIOD_ASIS, "PERST#");
 	if (IS_ERR(reset))
 		return PTR_ERR(reset);