Re: cpuidle: Default y for pseries

On Wed, 2012-01-11 at 20:37 -0200, Thadeu Lima de Souza Cascardo wrote:

On Tue, Jan 10, 2012 at 03:05:35PM -0000, Benjamin Herrenschmidt wrote:

quoted

We just replaced the pseries platform idle loops with a cpuidle backend,
however that means that you won't get any power saving and won't return
any unused idle time to the hypervisor unless cpuidle is enabled.

Thus is should default to y when pseries is enabled. I prefer that to
a select so we can still make it modular if we want to.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

---
Linus, do you want to just pick that up or should I put it into powerpc.git
and ask you to pull ? I will have 2 or 3 other fixes there later today,
but I wanted to make sure you were ok with the approach with this
specific one.

Hi, Ben.

Note that building with CONFIG_PSERIES_IDLE=m fails.

Ah ok. Well, making it built-in only makes sense anyway as I said
separately, so I think I'll just select it.

Cheers,
Ben.

  CC [M]  arch/powerpc/platforms/pseries/processor_idle.o
arch/powerpc/platforms/pseries/processor_idle.c:35: error: redefinition
of ‘update_smt_snooze_delay’
/root/linux/arch/powerpc/include/asm/system.h:230: note: previous
definition of ‘update_smt_snooze_delay’ was here
arch/powerpc/platforms/pseries/processor_idle.c:175: error: redefinition
of ‘pseries_notify_cpuidle_add_cpu’
/root/linux/arch/powerpc/include/asm/system.h:231: note: previous
definition of ‘pseries_notify_cpuidle_add_cpu’ was here
make[2]: *** [arch/powerpc/platforms/pseries/processor_idle.o] Error 1
make[1]: *** [arch/powerpc/platforms/pseries] Error 2
make: *** [arch/powerpc/platforms] Error 2

asm/system.h has empty inline implementations for
update_smt_snooze_delay and pseries_notify_cpuidle_add_cpu, which are
used when CONFIG_PSERIES_IDLE is undefined. Since those two functions
are used in core power architecture functions (store_smt_snooze_delay
at kernel/sysfs.c and smp_xics_setup_cpu at platforms/pseries/smp.c),
this requires some rework in these interactions or we should simply
disable PSERIES_IDLE to be built as a module for now.

Regards.
Cascardo.

quoted

diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index 7dbc4a8..62ca70d 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig

@@ -1,7 +1,8 @@
 
 config CPU_IDLE
 	bool "CPU idle PM support"
-	default ACPI
+	default y if ACPI
+	default y if PPC_PSERIES
 	help
 	  CPU idle is a generic framework for supporting software-controlled
 	  idle processor power management.  It includes modular cross-platform