PCI: imx6: Add reset-gpio-active-high boolean property to DT

Currently the reset-gpio DT property which controls the PCI bus device
reset signal defaults to active-low reset sequence (L=reset state,
H=operation state) plus the code in reset function isn't GPIO polarity
aware - it doesn't matter if the defined reset-gpio is active-low or
active-high, it will always result into active-low reset sequence.

I've tried to fix it properly and change the reset-gpio reset sequence to
be polarity-aware, but this patch has been accepted and then reverted as it
has introduced few backward incompatible issues:

1. Some DTBs, for example, imx6qdl-sabresd, don't define reset-gpio
polarity correctly:

  reset-gpio = <&gpio7 12 0>;

which means that it's defined as active-high, but in reality it's
active-low; thus it wouldn't work without a DTS fix.

2. The logic in the reset function is inverted:

	gpio_set_value_cansleep(imx6_pcie->reset_gpio, 0)
	msleep(100);
	gpio_set_value_cansleep(imx6_pcie->reset_gpio, 1);

so even if some of the i.MX6 boards had reset-gpio polarity defined
correctly in their DTSes, they would stop working.

As we can't break old DTBs, we can't fix them, so we need to introduce this
new DT reset-gpio-active-high boolean property so we can support boards
with active-high reset sequence.

This active-high reset sequence is for example needed on Apalis SoMs, where
GPIO1_IO28, used to PCIe reset is not connected directly to PERST# PCIe
signal, but it's ORed with RESETBMCU coming off the PMIC, and thus is
inverted, active-high.

Tested-by: Tim Harvey <tharvey@gateworks.com>	# Gateworks Ventana boards (which have active-low PERST#)
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>

diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
index 0561e88..636707d 100644 (file)
--- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
+++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
@@ -19,6 +19,12 @@ Optional properties:
 - fsl,tx-deemph-gen2-6db: Gen2 (6db) De-emphasis value. Default: 20
 - fsl,tx-swing-full: Gen2 TX SWING FULL value. Default: 127
 - fsl,tx-swing-low: TX launch amplitude swing_low value. Default: 127
+- reset-gpio: Should specify the GPIO for controlling the PCI bus device reset
+  signal. It's not polarity aware and defaults to active-low reset sequence
+  (L=reset state, H=operation state).
+- reset-gpio-active-high: If present then the reset sequence using the GPIO
+  specified in the "reset-gpio" property is reversed (H=reset state,
+  L=operation state).
 
 Additional required properties for imx6sx-pcie:
 - clock names: Must include the following additional entries:

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index 7cfe00e..0b8793d 100644 (file)
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -33,6 +33,7 @@
 
 struct imx6_pcie {
        int                     reset_gpio;
+       bool                    gpio_active_high;
        struct clk              *pcie_bus;
        struct clk              *pcie_phy;
        struct clk              *pcie_inbound_axi;
@@ -348,9 +349,11 @@ static int imx6_pcie_deassert_core_reset(struct pcie_port *pp)
 
        /* Some boards don't have PCIe reset GPIO. */
        if (gpio_is_valid(imx6_pcie->reset_gpio)) {
-               gpio_set_value_cansleep(imx6_pcie->reset_gpio, 0);
+               gpio_set_value_cansleep(imx6_pcie->reset_gpio,
+                                       imx6_pcie->gpio_active_high);
                msleep(100);
-               gpio_set_value_cansleep(imx6_pcie->reset_gpio, 1);
+               gpio_set_value_cansleep(imx6_pcie->reset_gpio,
+                                       !imx6_pcie->gpio_active_high);
        }
 
        if (imx6_pcie->is_imx6sx)
@@ -600,9 +603,14 @@ static int __init imx6_pcie_probe(struct platform_device *pdev)
 
        /* Fetch GPIOs */
        imx6_pcie->reset_gpio = of_get_named_gpio(np, "reset-gpio", 0);
+       imx6_pcie->gpio_active_high = of_property_read_bool(np,
+                                               "reset-gpio-active-high");
        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");
+                               imx6_pcie->gpio_active_high ?
+                                       GPIOF_OUT_INIT_HIGH :
+                                       GPIOF_OUT_INIT_LOW,
+                               "PCIe reset");
                if (ret) {
                        dev_err(&pdev->dev, "unable to get reset gpio\n");
                        return ret;