[PATCH v2 3/6] PPC: remove redundant cpuidle_idle_call()

Nicolas Pitre
2014-01-29T17:47:00Z

The core idle loop now takes care of it. However a few things need
checking:

- Invocation of cpuidle_idle_call() in pseries_lpar_idle() happened
through arch_cpu_idle() and was therefore always preceded by a call
to ppc64_runlatch_off(). To preserve this property now that
cpuidle_idle_call() is invoked directly from core code, a call to
ppc64_runlatch_off() has been added to idle_loop_prolog() in
platforms/pseries/processor_idle.c.

- Similarly, cpuidle_idle_call() was followed by ppc64_runlatch_off()
so a call to the later has been added to idle_loop_epilog().

- And since arch_cpu_idle() always made sure to re-enable IRQs if they
were not enabled, this is now
done in idle_loop_epilog() as well.

The above was made in order to keep the execution flow close to the
original. I don't know if that was strictly necessary. Someone well
aquainted with the platform details might find some room for possible
optimizations.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
---
arch/powerpc/platforms/pseries/processor_idle.c | 5 ++++
arch/powerpc/platforms/pseries/setup.c | 34 ++++++++++---------------
2 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/processor_idle.c b/arch/powerpc/platforms/pseries/processor_idle.c
index a166e38bd6..72ddfe3d2f 100644
--- a/arch/powerpc/platforms/pseries/processor_idle.c
+++ b/arch/powerpc/platforms/pseries/processor_idle.c
@@ -33,6 +33,7 @@ static struct cpuidle_state *cpuidle_state_table;

static inline void idle_loop_prolog(unsigned long *in_purr)
{
+ ppc64_runlatch_off();
*in_purr = mfspr(SPRN_PURR);
/*
* Indicate to the HV that we are idle. Now would be
@@ -49,6 +50,10 @@ static inline void idle_loop_epilog(unsigned long in_purr)
wait_cycles += mfspr(SPRN_PURR) - in_purr;
get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
get_lppaca()->idle = 0;
+
+ if (irqs_disabled())
+ local_irq_enable();
+ ppc64_runlatch_on();
}

static int snooze_loop(struct cpuidle_device *dev,
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index c1f1908587..7604c19d54 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -39,7 +39,6 @@
#include <linux/irq.h>
#include <linux/seq_file.h>
#include <linux/root_dev.h>
-#include <linux/cpuidle.h>
#include <linux/of.h>
#include <linux/kexec.h>

@@ -356,29 +355,24 @@ early_initcall(alloc_dispatch_log_kmem_cache);

static void pseries_lpar_idle(void)
{
- /* This would call on the cpuidle framework, and the back-end pseries
- * driver to go to idle states
+ /*
+ * Default handler to go into low thread priority and possibly
+ * low power mode by cedeing processor to hypervisor
*/
- if (cpuidle_idle_call()) {
- /* On error, execute default handler
- * to go into low thread priority and possibly
- * low power mode by cedeing processor to hypervisor
- */

- /* Indicate to hypervisor that we are idle. */
- get_lppaca()->idle = 1;
+ /* Indicate to hypervisor that we are idle. */
+ get_lppaca()->idle = 1;

- /*
- * Yield the processor to the hypervisor. We return if
- * an external interrupt occurs (which are driven prior
- * to returning here) or if a prod occurs from another
- * processor. When returning here, external interrupts
- * are enabled.
- */
- cede_processor();
+ /*
+ * Yield the processor to the hypervisor. We return if
+ * an external interrupt occurs (which are driven prior
+ * to returning here) or if a prod occurs from another
+ * processor. When returning here, external interrupts
+ * are enabled.
+ */
+ cede_processor();

- get_lppaca()->idle = 0;
- }
+ get_lppaca()->idle = 0;
}

/*
--
1.8.4.108.g55ea5f6