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| author | Pali Rohár <pali@kernel.org> | 2020-12-02 21:46:59 +0300 |
|---|---|---|
| committer | Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> | 2020-12-07 19:38:50 +0300 |
| commit | 1d1cd163d0de22a4041a6f1aeabcf78f80076539 (patch) | |
| tree | 2028b969a13ce64cfe1c1788d5f5d52dc8448620 /drivers/pci | |
| parent | f8394f232b1eab649ce2df5c5f15b0e528c92091 (diff) | |
| download | linux-1d1cd163d0de22a4041a6f1aeabcf78f80076539.tar.xz | |
PCI: aardvark: Update comment about disabling link training
According to PCI Express Base Specifications (rev 4.0, 6.6.1
"Conventional reset"), after fundamental reset a 100ms delay is needed
prior to enabling link training.
Update comment in code to reflect this requirement.
Link: https://lore.kernel.org/r/20201202184659.3795-1-pali@kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Diffstat (limited to 'drivers/pci')
| -rw-r--r-- | drivers/pci/controller/pci-aardvark.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c index 0be485a25327..f742da2a20ee 100644 --- a/drivers/pci/controller/pci-aardvark.c +++ b/drivers/pci/controller/pci-aardvark.c @@ -259,7 +259,14 @@ 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 (PCI Express Base Specification, REV. + * 4.0 PCI Express, February 19 2014, 6.6.1 Conventional Reset) 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. + */ reg = advk_readl(pcie, PCIE_CORE_CTRL0_REG); reg &= ~LINK_TRAINING_EN; advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG); |