x86/platform/uv: Disable UV BAU by default
For several years, the common practice has been to boot UVs with the
"nobau" parameter on the command line, to disable the BAU. We've
decided that it makes more sense to just disable the BAU by default in
the kernel, and provide the option to turn it on, if desired.
For now, having the on/off switch doesn't buy us any more than just
reversing the logic would, but we're working towards having the BAU
enabled by default on UV4. When those changes are in place, having the
on/off switch will make more sense than an enable flag, since the
default behavior will be different depending on the system version.
I've also added a bit of documentation for the new parameter to
Documentation/kernel-parameters.txt.
Signed-off-by: Alex Thorlton <athorlton@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1459451909-121845-1-git-send-email-athorlton@sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ecc74fa..893a709 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -131,6 +131,7 @@
More X86-64 boot options can be found in
Documentation/x86/x86_64/boot-options.txt .
X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
+ X86_UV SGI UV support is enabled.
XEN Xen support is enabled
In addition, the following text indicates that the option:
@@ -542,6 +543,13 @@
Format: <int> (must be >=0)
Default: 64
+ bau= [X86_UV] Enable the BAU on SGI UV. The default
+ behavior is to disable the BAU (i.e. bau=0).
+ Format: { "0" | "1" }
+ 0 - Disable the BAU.
+ 1 - Enable the BAU.
+ unset - Disable the BAU.
+
baycom_epp= [HW,AX25]
Format: <io>,<mode>