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authorPali Rohár <pali@kernel.org>2020-12-02 21:46:59 +0300
committerLorenzo Pieralisi <lorenzo.pieralisi@arm.com>2020-12-07 19:38:50 +0300
commit1d1cd163d0de22a4041a6f1aeabcf78f80076539 (patch)
tree2028b969a13ce64cfe1c1788d5f5d52dc8448620 /drivers/pci
parentf8394f232b1eab649ce2df5c5f15b0e528c92091 (diff)
downloadlinux-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.c9
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);