linux-kernel - [”PATCH” 1/5] PCI: armada8k: Disable LTSSM on link down interrupts

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Message-ID: <1618241456-27200-2-git-send-email-bpeled@marvell.com>
Date:   Mon, 12 Apr 2021 18:30:52 +0300
From:   <bpeled@...vell.com>
To:     <thomas.petazzoni@...tlin.com>, <lorenzo.pieralisi@....com>,
        <bhelgaas@...gle.com>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <sebastian.hesselbarth@...il.com>, <gregory.clement@...tlin.com>,
        <andrew@...n.ch>, <robh+dt@...nel.org>, <mw@...ihalf.com>,
        <jaz@...ihalf.com>, <kostap@...vell.com>, <nadavh@...vell.com>,
        <stefanc@...vell.com>, <oferh@...vell.com>, <bpeled@...vell.com>,
        "Marc St-Amand" <mstamand@...na.com>
Subject: [”PATCH” 1/5] PCI: armada8k: Disable LTSSM on link down interrupts

From: Ben Peled <bpeled@...vell.com>

When a PCI link down condition is detected, the link training state
machine must be disabled immediately.

Signed-off-by: Marc St-Amand <mstamand@...na.com>
Signed-off-by: Konstantin Porotchkin <kostap@...vell.com>
Signed-off-by: Ben Peled <bpeled@...vell.com>
---
 drivers/pci/controller/dwc/pcie-armada8k.c | 38 ++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-armada8k.c b/drivers/pci/controller/dwc/pcie-armada8k.c
index 13901f3..b2278b1 100644
--- a/drivers/pci/controller/dwc/pcie-armada8k.c
+++ b/drivers/pci/controller/dwc/pcie-armada8k.c
@@ -54,6 +54,10 @@ struct armada8k_pcie {
 #define PCIE_INT_C_ASSERT_MASK		BIT(11)
 #define PCIE_INT_D_ASSERT_MASK		BIT(12)
 
+#define PCIE_GLOBAL_INT_CAUSE2_REG	(PCIE_VENDOR_REGS_OFFSET + 0x24)
+#define PCIE_GLOBAL_INT_MASK2_REG	(PCIE_VENDOR_REGS_OFFSET + 0x28)
+#define PCIE_INT2_PHY_RST_LINK_DOWN	BIT(1)
+
 #define PCIE_ARCACHE_TRC_REG		(PCIE_VENDOR_REGS_OFFSET + 0x50)
 #define PCIE_AWCACHE_TRC_REG		(PCIE_VENDOR_REGS_OFFSET + 0x54)
 #define PCIE_ARUSER_REG			(PCIE_VENDOR_REGS_OFFSET + 0x5C)
@@ -193,6 +197,11 @@ static void armada8k_pcie_establish_link(struct armada8k_pcie *pcie)
 	       PCIE_INT_C_ASSERT_MASK | PCIE_INT_D_ASSERT_MASK;
 	dw_pcie_writel_dbi(pci, PCIE_GLOBAL_INT_MASK1_REG, reg);
 
+	/* Also enable link down interrupts */
+	reg = dw_pcie_readl_dbi(pci, PCIE_GLOBAL_INT_MASK2_REG);
+	reg |= PCIE_INT2_PHY_RST_LINK_DOWN;
+	dw_pcie_writel_dbi(pci, PCIE_GLOBAL_INT_MASK2_REG, reg);
+
 	if (!dw_pcie_link_up(pci)) {
 		/* Configuration done. Start LTSSM */
 		reg = dw_pcie_readl_dbi(pci, PCIE_GLOBAL_CONTROL_REG);
@@ -230,6 +239,35 @@ static irqreturn_t armada8k_pcie_irq_handler(int irq, void *arg)
 	val = dw_pcie_readl_dbi(pci, PCIE_GLOBAL_INT_CAUSE1_REG);
 	dw_pcie_writel_dbi(pci, PCIE_GLOBAL_INT_CAUSE1_REG, val);
 
+	val = dw_pcie_readl_dbi(pci, PCIE_GLOBAL_INT_CAUSE2_REG);
+
+	if (PCIE_INT2_PHY_RST_LINK_DOWN & val) {
+		u32 ctrl_reg = dw_pcie_readl_dbi(pci, PCIE_GLOBAL_CONTROL_REG);
+		/*
+		 * The link went down. Disable LTSSM immediately. This
+		 * unlocks the root complex config registers. Downstream
+		 * device accesses will return all-Fs
+		 */
+		ctrl_reg &= ~(PCIE_APP_LTSSM_EN);
+		dw_pcie_writel_dbi(pci, PCIE_GLOBAL_CONTROL_REG, ctrl_reg);
+		/*
+		 * Mask link down interrupts. They can be re-enabled once
+		 * the link is retrained.
+		 */
+		ctrl_reg = dw_pcie_readl_dbi(pci, PCIE_GLOBAL_INT_MASK2_REG);
+		ctrl_reg &= ~PCIE_INT2_PHY_RST_LINK_DOWN;
+		dw_pcie_writel_dbi(pci, PCIE_GLOBAL_INT_MASK2_REG, ctrl_reg);
+		/*
+		 * At this point a worker thread can be triggered to
+		 * initiate a link retrain. If link retrains were
+		 * possible, that is.
+		 */
+		dev_dbg(pci->dev, "%s: link went down\n", __func__);
+	}
+
+	/* Now clear the second interrupt cause. */
+	dw_pcie_writel_dbi(pci, PCIE_GLOBAL_INT_CAUSE2_REG, val);
+
 	return IRQ_HANDLED;
 }
 
-- 
2.7.4