igb_uio: add write combining option

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

To get internal_addr memory need to be mapped. But as memory could not be
mapped twice: with and without WC it should be skipped for WC. [1]

To do not spoil other drivers that potentially could use internal_addr,
parameter wc_activate adds possibility to skip it for those PMDs,
that do not use it.

[1] https://www.kernel.org/doc/ols/2008/ols2008v2-pages-135-144.pdf
	section 5.3 and 5.4

Signed-off-by: Rafal Kozik <rk@semihalf.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>

diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
index b3233f1..3398eac 100644 (file)
--- a/kernel/linux/igb_uio/igb_uio.c
+++ b/kernel/linux/igb_uio/igb_uio.c
@@ -30,6 +30,7 @@ struct rte_uio_pci_dev {
        int refcnt;
 };
 
+static int wc_activate;
 static char *intr_mode;
 static enum rte_intr_mode igbuio_intr_mode_preferred = RTE_INTR_MODE_MSIX;
 /* sriov sysfs */
@@ -375,9 +376,13 @@ igbuio_pci_setup_iomem(struct pci_dev *dev, struct uio_info *info,
        len = pci_resource_len(dev, pci_bar);
        if (addr == 0 || len == 0)
                return -1;
-       internal_addr = ioremap(addr, len);
-       if (internal_addr == NULL)
-               return -1;
+       if (wc_activate == 0) {
+               internal_addr = ioremap(addr, len);
+               if (internal_addr == NULL)
+                       return -1;
+       } else {
+               internal_addr = NULL;
+       }
        info->mem[n].name = name;
        info->mem[n].addr = addr;
        info->mem[n].internal_addr = internal_addr;
@@ -626,6 +631,9 @@ igbuio_pci_init_module(void)
                return -EINVAL;
        }
 
+       if (wc_activate != 0)
+               pr_info("wc_activate is set\n");
+
        ret = igbuio_config_intr_mode(intr_mode);
        if (ret < 0)
                return ret;
@@ -650,6 +658,12 @@ MODULE_PARM_DESC(intr_mode,
 "    " RTE_INTR_MODE_LEGACY_NAME "     Use Legacy interrupt\n"
 "\n");
 
+module_param(wc_activate, int, 0);
+MODULE_PARM_DESC(wc_activate,
+"Activate support for write combining (WC) (default=0)\n"
+"    0 - disable\n"
+"    other - enable\n");
+
 MODULE_DESCRIPTION("UIO driver for Intel IGB PCI cards");
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Intel Corporation");