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    Subject[PATCH 4.14 034/106] PCI: aardvark: Wait for endpoint to be ready before training link
    Date
    From: Remi Pommarel <repk@triplefau.lt>

    commit f4c7d053d7f77cd5c1a1ba7c7ce085ddba13d1d7 upstream.

    When configuring pcie reset pin from gpio (e.g. initially set by
    u-boot) to pcie function this pin goes low for a brief moment
    asserting the PERST# signal. Thus connected device enters fundamental
    reset process and link configuration can only begin after a minimal
    100ms delay (see [1]).

    Because the pin configuration comes from the "default" pinctrl it is
    implicitly configured before the probe callback is called:

    driver_probe_device()
    really_probe()
    ...
    pinctrl_bind_pins() /* Here pin goes from gpio to PCIE reset
    function and PERST# is asserted */
    ...
    drv->probe()

    [1] "PCI Express Base Specification", REV. 4.0
    PCI Express, February 19 2014, 6.6.1 Conventional Reset

    Signed-off-by: Remi Pommarel <repk@triplefau.lt>
    Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
    Signed-off-by: Marek Behún <kabel@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/pci/host/pci-aardvark.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    --- a/drivers/pci/host/pci-aardvark.c
    +++ b/drivers/pci/host/pci-aardvark.c
    @@ -362,6 +362,14 @@ static void advk_pcie_setup_hw(struct ad
    reg |= PIO_CTRL_ADDR_WIN_DISABLE;
    advk_writel(pcie, reg, PIO_CTRL);

    + /*
    + * PERST# signal could have been asserted by pinctrl subsystem before
    + * probe() callback has been called, making the endpoint going into
    + * fundamental reset. As required by PCI Express spec a delay for at
    + * least 100ms after such a reset before link training is needed.
    + */
    + msleep(PCI_PM_D3COLD_WAIT);
    +
    /* Start link training */
    reg = advk_readl(pcie, PCIE_CORE_LINK_CTRL_STAT_REG);
    reg |= PCIE_CORE_LINK_TRAINING;

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