Hi Nicolas,
On 01/27/2014 11:38 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 <n...@linaro.org>
> ---
> 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;
> }
>
> /*
>
Reviewed-by: Preeti U Murthy <pre...@linux.vnet.ibm.com>
The consequence of this would be for other Power platforms like PowerNV,
we will need to invoke ppc_runlatch_off() and ppc_runlatch_on() in each
of the idle routines since the idle_loop_prologue() and
idle_loop_epilogue() are not invoked by them, but we will take care of this.
Regards
Preeti U Murthy
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