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

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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 <[email protected]>	# Gateworks Ventana boards (which have active-low PERST#)
Signed-off-by: Petr Štetiar <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Lucas Stach <[email protected]>
Acked-by: Rob Herring <[email protected]>
This commit is contained in:
Petr Štetiar 2016-04-19 19:42:07 -05:00 • committed by Bjorn Helgaas
commit 3ea8529acc
2 changed files with 17 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

14
drivers/pci/host/pci-imx6.c
View file

@ -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;