From 2f4a63940bdd4425db02743d79b69cf8c26ece84 Mon Sep 17 00:00:00 2001
From: Rafal Kozik <rk@semihalf.com>
Date: Fri, 29 Jun 2018 15:54:07 +0200
Subject: [PATCH 005/166] bus/pci: enable write combining during mapping

Write combining (WC) increases NIC performance by making better
utilization of PCI bus, but cannot be used by all PMDs.

It will be enabled only if RTE_PCI_DRV_WC_ACTIVATE will be set in
drivers flags. For proper work also igb_uio driver must be loaded with
wc_activate set to 1.

When mapping PCI resources, firstly check if it support WC
and then try to use it.
In case of failure, it will fallback to normal mode.

Signed-off-by: Rafal Kozik <rk@semihalf.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
---
 drivers/bus/pci/linux/pci_uio.c | 47 ++++++++++++++++++++++++---------
 drivers/bus/pci/rte_bus_pci.h   |  2 ++
 2 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
index 2b2ad77ec7..12d384b63f 100644
--- a/drivers/bus/pci/linux/pci_uio.c
+++ b/drivers/bus/pci/linux/pci_uio.c
@@ -311,22 +311,19 @@ int
 pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
 		struct mapped_pci_resource *uio_res, int map_idx)
 {
-	int fd;
+	int fd = -1;
 	char devname[PATH_MAX];
 	void *mapaddr;
 	struct rte_pci_addr *loc;
 	struct pci_map *maps;
+	int wc_activate = 0;
+
+	if (dev->driver != NULL)
+		wc_activate = dev->driver->drv_flags & RTE_PCI_DRV_WC_ACTIVATE;
 
 	loc = &dev->addr;
 	maps = uio_res->maps;
 
-	/* update devname for mmap  */
-	snprintf(devname, sizeof(devname),
-			"%s/" PCI_PRI_FMT "/resource%d",
-			rte_pci_get_sysfs_path(),
-			loc->domain, loc->bus, loc->devid,
-			loc->function, res_idx);
-
 	/* allocate memory to keep path */
 	maps[map_idx].path = rte_malloc(NULL, sizeof(devname), 0);
 	if (maps[map_idx].path == NULL) {
@@ -338,11 +335,37 @@ pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
 	/*
 	 * open resource file, to mmap it
 	 */
-	fd = open(devname, O_RDWR);
-	if (fd < 0) {
-		RTE_LOG(ERR, EAL, "Cannot open %s: %s\n",
+	if (wc_activate) {
+		/* update devname for mmap  */
+		snprintf(devname, sizeof(devname),
+			"%s/" PCI_PRI_FMT "/resource%d_wc",
+			rte_pci_get_sysfs_path(),
+			loc->domain, loc->bus, loc->devid,
+			loc->function, res_idx);
+
+		if (access(devname, R_OK|W_OK) != -1) {
+			fd = open(devname, O_RDWR);
+			if (fd < 0)
+				RTE_LOG(INFO, EAL, "%s cannot be mapped. "
+					"Fall-back to non prefetchable mode.\n",
+					devname);
+		}
+	}
+
+	if (!wc_activate || fd < 0) {
+		snprintf(devname, sizeof(devname),
+			"%s/" PCI_PRI_FMT "/resource%d",
+			rte_pci_get_sysfs_path(),
+			loc->domain, loc->bus, loc->devid,
+			loc->function, res_idx);
+
+		/* then try to map resource file */
+		fd = open(devname, O_RDWR);
+		if (fd < 0) {
+			RTE_LOG(ERR, EAL, "Cannot open %s: %s\n",
 				devname, strerror(errno));
-		goto error;
+			goto error;
+		}
 	}
 
 	/* try mapping somewhere close to the end of hugepages */
diff --git a/drivers/bus/pci/rte_bus_pci.h b/drivers/bus/pci/rte_bus_pci.h
index c6af61d740..a1dff5efc3 100644
--- a/drivers/bus/pci/rte_bus_pci.h
+++ b/drivers/bus/pci/rte_bus_pci.h
@@ -164,6 +164,8 @@ struct rte_pci_bus {
 
 /** Device needs PCI BAR mapping (done with either IGB_UIO or VFIO) */
 #define RTE_PCI_DRV_NEED_MAPPING 0x0001
+/** Device needs PCI BAR mapping with enabled write combining (wc) */
+#define RTE_PCI_DRV_WC_ACTIVATE 0x0002
 /** Device driver supports link state interrupt */
 #define RTE_PCI_DRV_INTR_LSC	0x0008
 /** Device driver supports device removal interrupt */
-- 
2.25.1

