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Subject[PATCH 2/3] PCI: dwc: pci-dra7xx: Improve MSI IRQ handling
Date
We need to ensure that there are no pending MSI IRQ vector set (i.e
PCIE_MSI_INTR0_STATUS reads 0 at least once) before exiting
dra7xx_pcie_msi_irq_handler(). Else, the dra7xx PCIe wrapper will not
register new MSI IRQs even though PCIE_MSI_INTR0_STATUS shows IRQs are
pending. Therefore, keep calling dra7xx_pcie_msi_irq_handler() until it
returns IRQ_NONE, which suggests that PCIE_MSI_INTR0_STATUS is 0.

This fixes a bug, where PCIe wifi cards with 4 DMA queues like Intel
8260 used to throw following error and stall during ping/iperf3 tests.

[ 97.776310] iwlwifi 0000:01:00.0: Queue 9 stuck for 2500 ms.

Signed-off-by: Vignesh R <vigneshr@ti.com>
---
drivers/pci/dwc/pci-dra7xx.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c
index ed8558d638e5..3420cbf7b60a 100644
--- a/drivers/pci/dwc/pci-dra7xx.c
+++ b/drivers/pci/dwc/pci-dra7xx.c
@@ -254,14 +254,31 @@ static irqreturn_t dra7xx_pcie_msi_irq_handler(int irq, void *arg)
struct dra7xx_pcie *dra7xx = arg;
struct dw_pcie *pci = dra7xx->pci;
struct pcie_port *pp = &pci->pp;
+ int count = 0;
unsigned long reg;
u32 virq, bit;

reg = dra7xx_pcie_readl(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI);
+ dra7xx_pcie_writel(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI, reg);

switch (reg) {
case MSI:
- dw_handle_msi_irq(pp);
+ /*
+ * Need to make sure no MSI IRQs are pending before
+ * exiting handler, else the wrapper will not catch new
+ * IRQs. So loop around till dw_handle_msi_irq() returns
+ * IRQ_NONE
+ */
+ while (dw_handle_msi_irq(pp) != IRQ_NONE && count < 1000)
+ count++;
+
+ if (count == 1000) {
+ dev_err(pci->dev, "too much work in msi irq\n");
+ dra7xx_pcie_writel(dra7xx,
+ PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI,
+ reg);
+ return IRQ_HANDLED;
+ }
break;
case INTA:
case INTB:
@@ -275,8 +292,6 @@ static irqreturn_t dra7xx_pcie_msi_irq_handler(int irq, void *arg)
break;
}

- dra7xx_pcie_writel(dra7xx, PCIECTRL_DRA7XX_CONF_IRQSTATUS_MSI, reg);
-
return IRQ_HANDLED;
}

--
2.16.1
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