[6/9] PPC: remove redundant cpuidle_idle_call()

Message ID 1390802904-28399-7-git-send-email-nicolas.pitre@linaro.org
State New
Headers show

Commit Message

Nicolas Pitre Jan. 27, 2014, 6:08 a.m.
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>
---
 arch/powerpc/platforms/pseries/processor_idle.c |  5 ++++
 arch/powerpc/platforms/pseries/setup.c          | 34 ++++++++++---------------
 2 files changed, 19 insertions(+), 20 deletions(-)

Comments

Daniel Lezcano Jan. 27, 2014, 8:35 a.m. | #1
On 01/27/2014 07:08 AM, Nicolas Pitre wrote:
> 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>

Added Preeti U Murthy as recipient.

> ---
>   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;
>   }
>
>   /*
>

Patch

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;
 }
 
 /*