linux-kernel - [PATCH V3 3/5] PCI: tegra194: Disable interrupts before entering L2

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Date:   Wed, 23 Jun 2021 15:35:23 +0530
From:   Om Prakash Singh <omp@...dia.com>
To:     <kw@...ux.com>, <helgaas@...nel.org>, <vidyas@...dia.com>,
        <lorenzo.pieralisi@....com>, <bhelgaas@...gle.com>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>
CC:     <linux-tegra@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <kthota@...dia.com>,
        <mmaddireddy@...dia.com>, Om Prakash Singh <omp@...dia.com>
Subject: [PATCH V3 3/5] PCI: tegra194: Disable interrupts before entering L2

In suspend_noirq() call if link doesn't goto L2, PERST# is asserted
to bring link to detect state. However, this is causing surprise
link down AER error. Since Kernel is executing noirq suspend calls,
AER interrupt is not processed. PME and AER are shared interrupts
and PCIe subsystem driver enables wake capability of PME irq during
suspend. So this AER will cause suspend failure due to pending
AER interrupt.

After PCIe link is in L2, interrupts are not expected since PCIe
controller will be in reset state. Disable PCIe interrupts before
going to L2 state to avoid pending AER interrupt.

Signed-off-by: Om Prakash Singh <omp@...dia.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@...gle.com>
Acked-by: Vidya Sagar <vidyas@...dia.com>
---
 drivers/pci/controller/dwc/pcie-tegra194.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 66e00b276cd3..64ec0da31b5b 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -1593,6 +1593,16 @@ static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
 		return;
 	}
 
+	/*
+	 * PCIe controller exits from L2 only if reset is applied, so
+	 * controller doesn't handle interrupts. But in cases where
+	 * L2 entry fails, PERST# is asserted which can trigger surprise
+	 * link down AER. However this function call happens in
+	 * suspend_noirq(), so AER interrupt will not be processed.
+	 * Disable all interrupts to avoid such a scenario.
+	 */
+	appl_writel(pcie, 0x0, APPL_INTR_EN_L0_0);
+
 	if (tegra_pcie_try_link_l2(pcie)) {
 		dev_info(pcie->dev, "Link didn't transition to L2 state\n");
 		/*
-- 
2.17.1