On Thu, Sep 24, 2020 at 10:46:18AM +0200, Pali Rohár wrote: > It is not HW bug or workaround for some cards but it is requirement by PCI > Express spec. After fundamental reset is needed 100ms delay prior enabling > link training. So update comment in code to reflect this requirement. > > Signed-off-by: Pali Rohár <p...@kernel.org> > --- > drivers/pci/controller/pci-aardvark.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/pci-aardvark.c > b/drivers/pci/controller/pci-aardvark.c > index 50ab6d7519ae..19b9b79226e5 100644 > --- a/drivers/pci/controller/pci-aardvark.c > +++ b/drivers/pci/controller/pci-aardvark.c > @@ -259,7 +259,12 @@ static void advk_pcie_issue_perst(struct advk_pcie *pcie) > if (!pcie->reset_gpio) > return; > > - /* PERST does not work for some cards when link training is enabled */ > + /* > + * As required by PCI Express spec a delay for at least 100ms after > + * de-asserting PERST# signal is needed before link training is enabled. > + * So ensure that link training is disabled prior de-asserting PERST# > + * signal to fulfill that PCI Express spec requirement.
Can you please include the spec citation here? In the PCIe base spec, PERST# is only mentioned in PCIe r5.0, sec 6.6.1, and I don't see the connection there to 100ms between de-assert of PERST# and enabling link training. Sec 6.1.1 does talk about 100ms before sending config requests (for ports that support <= 5 GT/s), and 100ms after link training completes (for ports that support > 5 GT/s). Maybe there's more language in a form-factor spec or something? > + */ > reg = advk_readl(pcie, PCIE_CORE_CTRL0_REG); > reg &= ~LINK_TRAINING_EN; > advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG); > -- > 2.20.1 >
