linux-kernel - [PATCH 4.4 43/51] PCI: altera: Poll for link up status after retraining the link

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Message-Id: <20190115154853.398742826@linuxfoundation.org>
Date:   Tue, 15 Jan 2019 17:35:39 +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 43/51] PCI: altera: Poll for link up 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 3a928e98a833e1a470a60d2fedf3c55502185fb7 upstream.

Some PCIe devices take a long time to reach link up state after retrain.
Poll for link up status after retraining the link.  This is to make sure
the link is up before we access configuration space.

[bhelgaas: changelog]
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 |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/drivers/pci/host/pcie-altera.c
+++ b/drivers/pci/host/pcie-altera.c
@@ -61,6 +61,8 @@
 #define TLP_LOOP			500
 #define RP_DEVFN			0
 
+#define LINK_UP_TIMEOUT			5000
+
 #define INTX_NUM			4
 
 #define DWORD_MASK			3
@@ -101,6 +103,7 @@ static void altera_pcie_retrain(struct p
 {
 	u16 linkcap, linkstat;
 	struct altera_pcie *pcie = dev->bus->sysdata;
+	int timeout =  0;
 
 	if (!altera_pcie_link_is_up(pcie))
 		return;
@@ -115,9 +118,16 @@ static void altera_pcie_retrain(struct p
 		return;
 
 	pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &linkstat);
-	if ((linkstat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB)
+	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);
+		}
+	}
 }
 DECLARE_PCI_FIXUP_EARLY(0x1172, PCI_ANY_ID, altera_pcie_retrain);