[PATCH i-g-t v10 1/2] lib/igt_device: Add API to get pci device upstream port

[Karthik Poosa <karthik.poosa@intel.com>]

Add API igt_device_get_pci_upstream_port() to get pci device's
upstream port.
This API returns struct pci_device* of the upstream port that is closest
to the root port within the device's hierarchy.

v2: Avoid igt_require in igt_device_get_pci_usp(). (Kamil)

v3: Rename igt_device_get_pci_usp() to
    igt_device_get_pci_upstream_port(). (Kamil)

v4: Use device type from pci express capability of pci config space
    to identify upstream port. (Badal)

v5: Search for upstream port only two levels up of the endpoint as we want
    to verify ASPM only on PCIe link on which GPU card is present.

v6: Add missing spaces and new lines as per coding guidelines. (Kamil)

Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
Reviewed-by: Badal Nilawar <badal.nilawar@intel.com>
---
 lib/igt_device.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 lib/igt_device.h |  1 +
 lib/igt_pci.h    |  2 ++
 3 files changed, 46 insertions(+)

diff --git a/lib/igt_device.c b/lib/igt_device.c
index c24f6a58d..c617a98bc 100644
--- a/lib/igt_device.c
+++ b/lib/igt_device.c
@@ -32,6 +32,7 @@
 #include "igt.h"
 #include "igt_device.h"
 #include "igt_sysfs.h"
+#include "igt_pci.h"
 
 int __igt_device_set_master(int fd)
 {
@@ -308,3 +309,45 @@ void igt_device_get_pci_slot_name(int fd, char *pci_slot_name)
 	snprintf(pci_slot_name, NAME_MAX, "%04x:%02x:%02x.%01x",
 		 pci_dev->domain, pci_dev->bus, pci_dev->dev, pci_dev->func);
 }
+
+/**
+ * igt_device_get_pci_upstream_port:
+ * @fd: fd of the GPU endpoint.
+ *
+ * Looks up for the pci device's upstream port using libpciaccess.
+ *
+ * Returns:
+ * The pci_device of upstream port of the device referenced by fd, NULL on any failures.
+ */
+struct pci_device *
+igt_device_get_pci_upstream_port(int fd)
+{
+	struct pci_device *pci_dev = NULL;
+	uint8_t device_type = 0;
+	int offset = 0;
+	int level = 0;
+
+	pci_dev = __igt_device_get_pci_device(fd, 0);
+	if (!pci_dev) {
+		igt_warn("Couldn't get pci device for fd %d\n", fd);
+		return NULL;
+	}
+
+	for (pci_dev = pci_device_get_parent_bridge(pci_dev); (pci_dev && (level < 2));
+	     pci_dev = pci_device_get_parent_bridge(pci_dev), level++) {
+		igt_debug("PCI device %04x:%02x:%02x.%01x\n",  pci_dev->domain, pci_dev->bus,
+			  pci_dev->dev, pci_dev->func);
+		offset = find_pci_cap_offset(pci_dev, PCI_EXPRESS_CAP_ID);
+		if (offset <= 0) {
+			igt_warn("PCI Express Capability not found\n");
+			return NULL;
+		}
+
+		igt_assert(!pci_device_cfg_read_u8(pci_dev, &device_type,
+						   offset + PCI_DEVICE_TYPE_OFFSET));
+		if ((device_type >> 4) == PCI_DEVICE_TYPE_UPSTREAM_PORT)
+			return pci_dev;
+	}
+
+	return NULL;
+}
diff --git a/lib/igt_device.h b/lib/igt_device.h
index dad7bb047..781a72235 100644
--- a/lib/igt_device.h
+++ b/lib/igt_device.h
@@ -35,6 +35,7 @@ int igt_device_get_card_index(int fd);
 struct pci_device *igt_device_get_pci_device(int fd);
 struct pci_device *__igt_device_get_pci_device(int fd, unsigned int vf_id);
 struct pci_device *igt_device_get_pci_root_port(int fd);
+struct pci_device *igt_device_get_pci_upstream_port(int fd);
 
 void igt_device_get_pci_slot_name(int fd, char *pci_slot_name);
 #endif /* __IGT_DEVICE_H__ */
diff --git a/lib/igt_pci.h b/lib/igt_pci.h
index 92b9cc392..84355e9dd 100644
--- a/lib/igt_pci.h
+++ b/lib/igt_pci.h
@@ -20,6 +20,8 @@ enum pci_cap_id {
 	PCI_EXPRESS_CAP_ID = 0x10
 };
 
+#define PCI_DEVICE_TYPE_OFFSET 0x2
+#define PCI_DEVICE_TYPE_UPSTREAM_PORT	0x5
 #define PCI_SLOT_CAP_OFFSET 0x14
 #define  PCI_SLOT_PWR_CTRL_PRESENT (1 << 1)
 
-- 
2.25.1