On Wed, 7 May 2014, Olof Johansson wrote:

On Wed, May 07, 2014 at 10:44:40PM +0800, Haojian Zhuang wrote:

quoted

Add the CONFIG_MCPM_QUAD_CLUSTER configuration to enlarge cluster number
from 2 to 4.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
---
 arch/arm/Kconfig            | 9 +++++++++
 arch/arm/include/asm/mcpm.h | 5 +++++
 2 files changed, 14 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 0e52a2c..624829f 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -1575,6 +1575,15 @@ config MCPM
 	  for (multi-)cluster based systems, such as big.LITTLE based
 	  systems.
 
+config MCPM_QUAD_CLUSTER
+	bool "Enable Quad clusters in MCPM"
+	depends on MCPM
+	help
+	  To avoid wasting resources unnecessarily, MCPM only supports up
+	  to 2 clusters by default.
+	  Platforms with 3 or 4 clusters that use MCPM must select this
+	  option to allow the additional clusters to be managed.
+

Why don't you add an integer config instead, i.e. MCPM_MAX_CLUSTERS, and let
that set MAX_NR_CLUSTERS?

I requested for this config symbol not to be visible to users (the 
prompt string should be removed) and be selected by those platforms that 
need it instead.  And there is no way to specify an actual value with 
'select'. And that wouldn't work in a multi-platform config where 
different platforms could fight over a different value anyway.

I also prefer to keep some control on the actual number that can be used 
here so not to let people go overboard with it.  If this grows too big 
we'll have to consider some dynamic allocation instead.

See previous discussion here:

http://article.gmane.org/gmane.linux.ports.arm.kernel/315228


Nicolas