On Wed, Apr 6, 2016 at 5:36 AM, Petr Štetiar <ynezz@xxxxxxx> wrote:
> 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 changed 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 of the DTBs as for example imx6qdl-sabresd, doesn'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 DTS fix.
>
> 2. The logic in 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 and that's why 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.
>
> Signed-off-by: Petr Štetiar <ynezz@xxxxxxx>
> ---
> Changes since v1:
>
> * Added documentation of reset-gpio and reset-gpio-active-high DT properties
> * Removed unnecessary double negation of GPIO value
>
> Changes since v2:
>
> * Changed commit message so it explains in more detail why we need new DT
> property
> * Changed PHY to 'bus device' in binding's documentation
>
> Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt | 6 ++++++
> drivers/pci/host/pci-imx6.c | 14 +++++++++++---
> 2 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt
> index 3be80c6..072efbf 100644
> --- 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. Its 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).
>
> Example:
>
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index 2f817fa..17f4cc3 100644
> --- 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;
> @@ -310,9 +311,11 @@ 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);
> }
> return 0;
>
> @@ -546,9 +549,14 @@ 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;
> --
> 1.9.1
>
Tested on Gateworks Ventana boards (which have active-low PERST#)
Tested-by: Tim Harvey <tharvey@xxxxxxxxxxxxx>
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