PCI/DPC: Leave interrupts enabled while handling event

Now that the DPC driver clears the interrupt status before exiting the
IRQ handler, we don't need to abuse the DPC control register to know if
a shared interrupt is for a new DPC event: a DPC port can not trigger
a second interrupt until the host clears the trigger status later in the
work queue handler.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Sinan Kaya <okaya@kernel.org>
Reviewed-by: Oza Pawandeep <poza@codeaurora.org>

drivers/pci/pcie/dpc.c

@@ -77,7 +77,7 @@ static pci_ers_result_t dpc_reset_link(struct pci_dev *pdev)
 	struct dpc_dev *dpc;
 	struct pcie_device *pciedev;
 	struct device *devdpc;
-	u16 cap, ctl;
+	u16 cap;
 
 	/*
 	 * DPC disables the Link automatically in hardware, so it has
@@ -105,10 +105,6 @@ static pci_ers_result_t dpc_reset_link(struct pci_dev *pdev)
 	pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS,
 			      PCI_EXP_DPC_STATUS_TRIGGER);
 
-	pci_read_config_word(pdev, cap + PCI_EXP_DPC_CTL, &ctl);
-	pci_write_config_word(pdev, cap + PCI_EXP_DPC_CTL,
-			      ctl | PCI_EXP_DPC_CTL_INT_EN);
-
 	return PCI_ERS_RESULT_RECOVERED;
 }
 
@@ -183,16 +179,11 @@ static irqreturn_t dpc_irq(int irq, void *context)
 	struct dpc_dev *dpc = (struct dpc_dev *)context;
 	struct pci_dev *pdev = dpc->dev->port;
 	struct device *dev = &dpc->dev->device;
-	u16 cap = dpc->cap_pos, ctl, status, source, reason, ext_reason;
-
-	pci_read_config_word(pdev, cap + PCI_EXP_DPC_CTL, &ctl);
-
-	if (!(ctl & PCI_EXP_DPC_CTL_INT_EN) || ctl == (u16)(~0))
-		return IRQ_NONE;
+	u16 cap = dpc->cap_pos, status, source, reason, ext_reason;
 
 	pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
 
-	if (!(status & PCI_EXP_DPC_STATUS_INTERRUPT))
+	if (!(status & PCI_EXP_DPC_STATUS_INTERRUPT) || status == (u16)(~0))
 		return IRQ_NONE;
 
 	if (!(status & PCI_EXP_DPC_STATUS_TRIGGER)) {
@@ -201,9 +192,6 @@ static irqreturn_t dpc_irq(int irq, void *context)
 		return IRQ_HANDLED;
 	}
 
-	pci_write_config_word(pdev, cap + PCI_EXP_DPC_CTL,
-			      ctl & ~PCI_EXP_DPC_CTL_INT_EN);
-
 	pci_read_config_word(pdev, cap + PCI_EXP_DPC_SOURCE_ID,
 			     &source);
 
@@ -226,9 +214,8 @@ static irqreturn_t dpc_irq(int irq, void *context)
 
 	pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS,
 			      PCI_EXP_DPC_STATUS_INTERRUPT);
-
-	schedule_work(&dpc->work);
-
+	if (status & PCI_EXP_DPC_STATUS_TRIGGER)
+		schedule_work(&dpc->work);
 	return IRQ_HANDLED;
 }