From 6dcb92ef836b811302e8b2409f43db94a746278a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Pali=20Roh=C3=A1r?= Date: Fri, 14 Jan 2022 19:29:52 +0800 Subject: [PATCH] PCI: aardvark: Update comment about disabling link training MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit stable inclusion from stable-v5.10.83 commit e7f2e2c758ea55df94356d5f0341874ab9179110 bugzilla: 185879 https://gitee.com/openeuler/kernel/issues/I4QUVG Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e7f2e2c758ea55df94356d5f0341874ab9179110 -------------------------------- 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 Signed-off-by: Lorenzo Pieralisi Signed-off-by: Marek Behún Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chen Jun Signed-off-by: Zheng Zengkai --- drivers/pci/controller/pci-aardvark.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c index 71fdaf010ad1..a19562de6186 100644 --- a/drivers/pci/controller/pci-aardvark.c +++ b/drivers/pci/controller/pci-aardvark.c @@ -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); -- GitLab