linux-kernel - [PATCH 4.14 035/106] PCI: aardvark: Train link immediately after enabling training

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Date:   Mon,  6 Dec 2021 15:55:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tomasz Maciej Nowak <tmn505@...il.com>,
        Pali Rohár <pali@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Marek Behún <kabel@...nel.org>
Subject: [PATCH 4.14 035/106] PCI: aardvark: Train link immediately after enabling training

From: Pali Rohár <pali@...nel.org>

commit 6964494582f56a3882c2c53b0edbfe99eb32b2e1 upstream.

Adding even 100ms (PCI_PM_D3COLD_WAIT) delay between enabling link
training and starting link training causes detection issues with some
buggy cards (such as Compex WLE900VX).

Move the code which enables link training immediately before the one
which starts link traning.

This fixes detection issues of Compex WLE900VX card on Turris MOX after
cold boot.

Link: https://lore.kernel.org/r/20200430080625.26070-2-pali@kernel.org
Fixes: f4c7d053d7f7 ("PCI: aardvark: Wait for endpoint to be ready...")
Tested-by: Tomasz Maciej Nowak <tmn505@...il.com>
Signed-off-by: Pali Rohár <pali@...nel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Acked-by: Rob Herring <robh@...nel.org>
Acked-by: Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Signed-off-by: Marek Behún <kabel@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/pci/host/pci-aardvark.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/drivers/pci/host/pci-aardvark.c
+++ b/drivers/pci/host/pci-aardvark.c
@@ -324,11 +324,6 @@ static void advk_pcie_setup_hw(struct ad
 	reg |= LANE_COUNT_1;
 	advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG);
 
-	/* Enable link training */
-	reg = advk_readl(pcie, PCIE_CORE_CTRL0_REG);
-	reg |= LINK_TRAINING_EN;
-	advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG);
-
 	/* Enable MSI */
 	reg = advk_readl(pcie, PCIE_CORE_CTRL2_REG);
 	reg |= PCIE_CORE_CTRL2_MSI_ENABLE;
@@ -370,7 +365,15 @@ static void advk_pcie_setup_hw(struct ad
 	 */
 	msleep(PCI_PM_D3COLD_WAIT);
 
-	/* Start link training */
+	/* Enable link training */
+	reg = advk_readl(pcie, PCIE_CORE_CTRL0_REG);
+	reg |= LINK_TRAINING_EN;
+	advk_writel(pcie, reg, PCIE_CORE_CTRL0_REG);
+
+	/*
+	 * Start link training immediately after enabling it.
+	 * This solves problems for some buggy cards.
+	 */
 	reg = advk_readl(pcie, PCIE_CORE_LINK_CTRL_STAT_REG);
 	reg |= PCIE_CORE_LINK_TRAINING;
 	advk_writel(pcie, reg, PCIE_CORE_LINK_CTRL_STAT_REG);