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PCI: aardvark: Update comment about disabling link training

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commit 1d1cd163d0de22a4041a6f1aeabcf78f80076539 upstream.

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>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pali Rohár 2020-12-02 19:46:59 +01:00 committed by Greg Kroah-Hartman
parent 2b7bc1c4b2
commit e7f2e2c758
1 changed files with 8 additions and 1 deletions
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9
drivers/pci/controller/pci-aardvark.c
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@ -389,7 +389,14 @@ 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);