linux-kernel - [PATCH 4.4 44/51] PCI: altera: Poll for link training status after retraining the link

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Message-Id: <20190115154853.486522240@linuxfoundation.org>
Date:   Tue, 15 Jan 2019 17:35:40 +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, Ley Foon Tan <lftan@...era.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Claudius Heine <claudius.heine.ext@...mens.com>
Subject: [PATCH 4.4 44/51] PCI: altera: Poll for link training status after retraining the link

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ley Foon Tan <lftan@...era.com>

commit 411dc32d8810e0a204c799ce5c97cb56990de1cb upstream.

Poll for link training status is cleared before poll for link up status.
This can help to get the reliable link up status, especially when PCIe is
in Gen 3 speed.

Signed-off-by: Ley Foon Tan <lftan@...era.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Claudius Heine <claudius.heine.ext@...mens.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/pci/host/pcie-altera.c |   45 +++++++++++++++++++++++++++++++++--------
 1 file changed, 37 insertions(+), 8 deletions(-)

--- a/drivers/pci/host/pcie-altera.c
+++ b/drivers/pci/host/pcie-altera.c
@@ -61,7 +61,8 @@
 #define TLP_LOOP			500
 #define RP_DEVFN			0
 
-#define LINK_UP_TIMEOUT			5000
+#define LINK_UP_TIMEOUT			HZ
+#define LINK_RETRAIN_TIMEOUT		HZ
 
 #define INTX_NUM			4
 
@@ -99,11 +100,44 @@ static bool altera_pcie_link_is_up(struc
 	return !!((cra_readl(pcie, RP_LTSSM) & RP_LTSSM_MASK) == LTSSM_L0);
 }
 
+static void altera_wait_link_retrain(struct pci_dev *dev)
+{
+	u16 reg16;
+	unsigned long start_jiffies;
+	struct altera_pcie *pcie = dev->bus->sysdata;
+
+	/* Wait for link training end. */
+	start_jiffies = jiffies;
+	for (;;) {
+		pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &reg16);
+		if (!(reg16 & PCI_EXP_LNKSTA_LT))
+			break;
+
+		if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT)) {
+			dev_err(&pcie->pdev->dev, "link retrain timeout\n");
+			break;
+		}
+		udelay(100);
+	}
+
+	/* Wait for link is up */
+	start_jiffies = jiffies;
+	for (;;) {
+		if (altera_pcie_link_is_up(pcie))
+			break;
+
+		if (time_after(jiffies, start_jiffies + LINK_UP_TIMEOUT)) {
+			dev_err(&pcie->pdev->dev, "link up timeout\n");
+			break;
+		}
+		udelay(100);
+	}
+}
+
 static void altera_pcie_retrain(struct pci_dev *dev)
 {
 	u16 linkcap, linkstat;
 	struct altera_pcie *pcie = dev->bus->sysdata;
-	int timeout =  0;
 
 	if (!altera_pcie_link_is_up(pcie))
 		return;
@@ -121,12 +155,7 @@ static void altera_pcie_retrain(struct p
 	if ((linkstat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB) {
 		pcie_capability_set_word(dev, PCI_EXP_LNKCTL,
 					 PCI_EXP_LNKCTL_RL);
-		while (!altera_pcie_link_is_up(pcie)) {
-			timeout++;
-			if (timeout > LINK_UP_TIMEOUT)
-				break;
-			udelay(5);
-		}
+		altera_wait_link_retrain(dev);
 	}
 }
 DECLARE_PCI_FIXUP_EARLY(0x1172, PCI_ANY_ID, altera_pcie_retrain);