diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index f9cc2e10b676..c570892b2090 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -9,6 +9,7 @@
  * Copyright (C) 2011 Advanced Micro Devices,
  */
 
+#include <linux/bitfield.h>
 #include <linux/export.h>
 #include <linux/pci-ats.h>
 #include <linux/pci.h>
@@ -480,8 +481,6 @@ int pci_pasid_features(struct pci_dev *pdev)
 }
 EXPORT_SYMBOL_GPL(pci_pasid_features);
 
-#define PASID_NUMBER_SHIFT	8
-#define PASID_NUMBER_MASK	(0x1f << PASID_NUMBER_SHIFT)
 /**
  * pci_max_pasids - Get maximum number of PASIDs supported by device
  * @pdev: PCI device structure
@@ -503,9 +502,7 @@ int pci_max_pasids(struct pci_dev *pdev)
 
 	pci_read_config_word(pdev, pasid + PCI_PASID_CAP, &supported);
 
-	supported = (supported & PASID_NUMBER_MASK) >> PASID_NUMBER_SHIFT;
-
-	return (1 << supported);
+	return (1 << FIELD_GET(PCI_PASID_CAP_WIDTH, supported));
 }
 EXPORT_SYMBOL_GPL(pci_max_pasids);
 #endif /* CONFIG_PCI_PASID */
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index f35d73efe223..4f226db4c1dc 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -932,6 +932,7 @@
 #define PCI_PASID_CAP		0x04    /* PASID feature register */
 #define  PCI_PASID_CAP_EXEC	0x0002	/* Exec permissions Supported */
 #define  PCI_PASID_CAP_PRIV	0x0004	/* Privilege Mode Supported */
+#define  PCI_PASID_CAP_WIDTH	0x1f00
 #define PCI_PASID_CTRL		0x06    /* PASID control register */
 #define  PCI_PASID_CTRL_ENABLE	0x0001	/* Enable bit */
 #define  PCI_PASID_CTRL_EXEC	0x0002	/* Exec permissions Enable */