diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 71fdaf010ad11ce2f4d83c265781bf293b5fc140..a19562de618630c140dfc82c18f5e7d3eea50b1e 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);