PCI/DPC: Add and use DPC Status register field definitions

Add definitions for DPC Status register fields and use them in the code.
No functional change intended.

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

drivers/pci/pcie/pcie-dpc.c

@@ -211,8 +211,8 @@ static irqreturn_t dpc_irq(int irq, void *context)
 	dev_info(dev, "DPC containment event, status:%#06x source:%#06x\n",
 		status, source);
 
-	reason = (status >> 1) & 0x3;
-	ext_reason = (status >> 5) & 0x3;
+	reason = (status & PCI_EXP_DPC_STATUS_TRIGGER_RSN) >> 1;
+	ext_reason = (status & PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT) >> 5;
 
 	dev_warn(dev, "DPC %s detected, remove downstream devices\n",
 		 (reason == 0) ? "unmasked uncorrectable error" :

include/uapi/linux/pci_regs.h

@@ -979,8 +979,10 @@
 
 #define PCI_EXP_DPC_STATUS		8	/* DPC Status */
 #define  PCI_EXP_DPC_STATUS_TRIGGER	0x01	/* Trigger Status */
+#define  PCI_EXP_DPC_STATUS_TRIGGER_RSN	0x06	/* Trigger Reason */
 #define  PCI_EXP_DPC_STATUS_INTERRUPT	0x08	/* Interrupt Status */
 #define  PCI_EXP_DPC_RP_BUSY		0x10	/* Root Port Busy */
+#define  PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT 0x60 /* Trig Reason Extension */
 
 #define PCI_EXP_DPC_SOURCE_ID		10	/* DPC Source Identifier */