PCI: aardvark: Assert PERST# when unbinding driver

commit 1f54391 upstream.

Put the PCIe card into reset by asserting PERST# signal when unbinding
driver. It doesn't make sense to leave the card working if it can't
communicate with the host. This should also save some power.

Link: https://lore.kernel.org/r/20211130172913.9727-10-kabel@kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/pci/controller/pci-aardvark.c

@@ -1721,6 +1721,10 @@ static int advk_pcie_remove(struct platform_device *pdev)
 	/* Free config space for emulated root bridge */
 	pci_bridge_emul_cleanup(&pcie->bridge);
 
+	/* Assert PERST# signal which prepares PCIe card for power down */
+	if (pcie->reset_gpio)
+		gpiod_set_value_cansleep(pcie->reset_gpio, 1);
+
 	/* Disable outbound address windows mapping */
 	for (i = 0; i < OB_WIN_COUNT; i++)
 		advk_pcie_disable_ob_win(pcie, i);