PCIe: Add L1 Sub-State support.

Enable L1 Sub-State when both root port and endpoint support it.

BUG=chrome-os-partner:31424
TEST=Build a image and run on Samus proto boards to check if the
settings are applied correctly. I just only have proto boars and
need someone having EVT boards to confirm the settings.
Signed-off-by: Kenji Chen <kenji.chen@intel.com>
Change-Id: Id1b5a52ff0b896f4531c4a6e68e70a2cea8c736a
Reviewed-on: https://chromium-review.googlesource.com/221436
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

src/include/device/pci.h

@@ -28,6 +28,7 @@
 struct pci_operations {
 	/* set the Subsystem IDs for the PCI device */
 	void (*set_subsystem)(device_t dev, unsigned vendor, unsigned device);
+	void (*set_L1_ss_latency)(device_t dev, unsigned int off);
 };
 
 /* Common pci bus operations */

src/include/device/pci_def.h

@@ -404,6 +404,12 @@
 #define PCI_EXT_CAP_ID_DSN	3
 #define PCI_EXT_CAP_ID_PWR	4
 
+/* Extended Capability lists*/
+#define PCIE_EXT_CAP_OFFSET	0x100
+#define  PCIE_EXT_CAP_AER_ID	0x0001
+#define  PCIE_EXT_CAP_L1SS_ID	0x001E
+#define  PCIE_EXT_CAP_LTR_ID	0x0018
+
 /* Advanced Error Reporting */
 #define PCI_ERR_UNCOR_STATUS	4	/* Uncorrectable Error Status */
 #define  PCI_ERR_UNC_TRAIN	0x00000001	/* Training */

src/include/device/pciexp.h

@@ -15,4 +15,5 @@ unsigned int pciexp_scan_bridge(device_t dev, unsigned int max);
 
 extern struct device_operations default_pciexp_ops_bus;
 
+unsigned int pciexp_find_extended_cap(device_t dev, unsigned int cap);
 #endif /* DEVICE_PCIEXP_H */