Author: cem
Date: Wed Nov 18 22:20:13 2015
New Revision: 291030
URL: https://svnweb.freebsd.org/changeset/base/291030
Log:
ntb_hw: Add tunable to disable write-combining
The tunable 'hw.ntb.enable_writecombine' may be set to zero to
administratively disable write combining the mapped NTB region.
Sponsored by: EMC / Isilon Storage Division
Modified:
head/sys/dev/ntb/ntb_hw/ntb_hw.c
Modified: head/sys/dev/ntb/ntb_hw/ntb_hw.c
==============================================================================
--- head/sys/dev/ntb/ntb_hw/ntb_hw.c Wed Nov 18 22:20:04 2015
(r291029)
+++ head/sys/dev/ntb/ntb_hw/ntb_hw.c Wed Nov 18 22:20:13 2015
(r291030)
@@ -326,6 +326,10 @@ SYSCTL_UINT(_hw_ntb, OID_AUTO, debug_lev
} \
} while (0)
+static unsigned g_ntb_enable_wc = 1;
+SYSCTL_UINT(_hw_ntb, OID_AUTO, enable_writecombine, CTLFLAG_RDTUN,
+ &g_ntb_enable_wc, 0, "Set to 1 to map memory windows write combining");
+
static struct ntb_hw_info pci_ids[] = {
/* XXX: PS/SS IDs left out until they are supported. */
{ 0x0C4E8086, "BWD Atom Processor S1200 Non-Transparent Bridge B2B",
@@ -766,10 +770,13 @@ map_memory_window_bar(struct ntb_softc *
save_bar_parameters(bar);
}
+ print_map_success(ntb, bar, "mw");
+ if (g_ntb_enable_wc == 0)
+ return (0);
+
/* Mark bar region as write combining to improve performance. */
rc = pmap_change_attr((vm_offset_t)bar->vbase, bar->size,
VM_MEMATTR_WRITE_COMBINING);
- print_map_success(ntb, bar, "mw");
if (rc == 0)
device_printf(ntb->device,
"Marked BAR%d v:[%p-%p] p:[%p-%p] as "
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