diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 174d1147081b..f48d06e2bb4d 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -682,6 +682,7 @@
 #define PCI_EXT_CAP_ID_PMUX	0x1A	/* Protocol Multiplexing */
 #define PCI_EXT_CAP_ID_PASID	0x1B	/* Process Address Space ID */
 #define PCI_EXT_CAP_ID_DPC	0x1D	/* Downstream Port Containment */
+#define PCI_EXT_CAP_ID_L1SS	0x1E	/* L1 PM Substates */
 #define PCI_EXT_CAP_ID_PTM	0x1F	/* Precision Time Measurement */
 #define PCI_EXT_CAP_ID_MAX	PCI_EXT_CAP_ID_PTM
 
@@ -985,4 +986,19 @@
 #define  PCI_PTM_CTRL_ENABLE		0x00000001  /* PTM enable */
 #define  PCI_PTM_CTRL_ROOT		0x00000002  /* Root select */
 
+/* L1 PM Substates */
+#define PCI_L1SS_CAP		    4	/* capability register */
+#define  PCI_L1SS_CAP_PCIPM_L1_2	 1	/* PCI PM L1.2 Support */
+#define  PCI_L1SS_CAP_PCIPM_L1_1	 2	/* PCI PM L1.1 Support */
+#define  PCI_L1SS_CAP_ASPM_L1_2		 4	/* ASPM L1.2 Support */
+#define  PCI_L1SS_CAP_ASPM_L1_1		 8	/* ASPM L1.1 Support */
+#define  PCI_L1SS_CAP_L1_PM_SS		16	/* L1 PM Substates Support */
+#define PCI_L1SS_CTL1		    8	/* Control Register 1 */
+#define  PCI_L1SS_CTL1_PCIPM_L1_2	1	/* PCI PM L1.2 Enable */
+#define  PCI_L1SS_CTL1_PCIPM_L1_1	2	/* PCI PM L1.1 Support */
+#define  PCI_L1SS_CTL1_ASPM_L1_2	4	/* ASPM L1.2 Support */
+#define  PCI_L1SS_CTL1_ASPM_L1_1	8	/* ASPM L1.1 Support */
+#define  PCI_L1SS_CTL1_L1SS_MASK	0x0000000F
+#define PCI_L1SS_CTL2		    0xC	/* Control Register 2 */
+
 #endif /* LINUX_PCI_REGS_H */