PCI: imx6: Make reset-gpio optional

Some boards do not have a PCIe reset GPIO.  To avoid probe failure on these
boards, make the reset GPIO optional as well.

[bhelgaas: whitespace fixes]
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Frank Li <lznuaa@gmail.com>
Cc: Harro Haan <hrhaan@gmail.com>
Cc: Mohit KUMAR <Mohit.KUMAR@st.com>
Cc: Pratyush Anand <pratyush.anand@st.com>
Cc: Richard Zhu <r65037@freescale.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Sean Cross <xobs@kosagi.com>
Cc: Siva Reddy Kallam <siva.kallam@samsung.com>
Cc: Srikanth T Shivanand <ts.srikanth@samsung.com>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Troy Kisky <troy.kisky@boundarydevices.com>
Cc: Yinghai Lu <yinghai@kernel.org>

Documentation/devicetree/bindings/pci/designware-pcie.txt

@@ -19,6 +19,8 @@ Required properties:
 	to define the mapping of the PCIe interface to interrupt
 	numbers.
 - num-lanes: number of lanes to use
+
+Optional properties:
 - reset-gpio: gpio pin number of power good signal
 
 Optional properties for fsl,imx6q-pcie

drivers/pci/host/pci-imx6.c

@@ -214,9 +214,12 @@ static int imx6_pcie_assert_core_reset(struct pcie_port *pp)
 	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR1,
 			IMX6Q_GPR1_PCIE_REF_CLK_EN, 0 << 16);
 
+	/* Some boards don't have PCIe reset GPIO. */
+	if (gpio_is_valid(imx6_pcie->reset_gpio)) {
 		gpio_set_value(imx6_pcie->reset_gpio, 0);
 		msleep(100);
 		gpio_set_value(imx6_pcie->reset_gpio, 1);
+	}
 
 	return 0;
 }
@@ -432,18 +435,14 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
 
 	/* Fetch GPIOs */
 	imx6_pcie->reset_gpio = of_get_named_gpio(np, "reset-gpio", 0);
-	if (!gpio_is_valid(imx6_pcie->reset_gpio)) {
-		dev_err(&pdev->dev, "no reset-gpio defined\n");
-		ret = -ENODEV;
-	}
-	ret = devm_gpio_request_one(&pdev->dev,
-				imx6_pcie->reset_gpio,
-				GPIOF_OUT_INIT_LOW,
-				"PCIe reset");
+	if (gpio_is_valid(imx6_pcie->reset_gpio)) {
+		ret = devm_gpio_request_one(&pdev->dev, imx6_pcie->reset_gpio,
+					    GPIOF_OUT_INIT_LOW, "PCIe reset");
 		if (ret) {
 			dev_err(&pdev->dev, "unable to get reset gpio\n");
 			return ret;
 		}
+	}
 
 	imx6_pcie->power_on_gpio = of_get_named_gpio(np, "power-on-gpio", 0);
 	if (gpio_is_valid(imx6_pcie->power_on_gpio)) {