Subject: Re: [RFC 2/3] powernv/cpuidle : Interface for an idle-stop dependency structure

From: Gautham R Shenoy <[email-masked]>
Date: Mon, 27 Apr 2020 19:17:11 +0530

On Sun, Apr 26, 2020 at 09:10:26PM -0500, Abhishek Goel wrote:
> This patch introduces the idea of having a dependency structure for
> idle-stop. The structure encapsulates the following:
> 1. Bitmask for version of idle-stop
> 2. Bitmask for propterties like ENABLE/DISABLE
> 3. Function pointer which helps handle how the stop must be invoked
> 
> This patch lays a foundation for other idle-stop versions to be added
> and handled cleanly based on their specified requirments.
> Currently it handles the existing "idle-stop" version by setting the
> discovery bits and the function pointer.
> 
> Earlier this patch was posted as part of this series :
> https://lkml.org/lkml/2020/3/4/589

Please see the review comments to the earlier version:
https://lkml.org/lkml/2020/4/8/245

I still feel that we don't need cpuidle_prop and stop_version to be
separate fields.

> 
> Signed-off-by: Pratik Rajesh Sampat <[email-masked]>
> Signed-off-by: Abhishek Goel <[email-masked]>
> ---
> 
>  v1->v2: This patch is newly added in this series.
> 
>  arch/powerpc/include/asm/processor.h  | 17 +++++++++++++++++
>  arch/powerpc/kernel/dt_cpu_ftrs.c     |  5 +++++
>  arch/powerpc/platforms/powernv/idle.c | 18 ++++++++++++++----
>  drivers/cpuidle/cpuidle-powernv.c     |  3 ++-
>  4 files changed, 38 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
> index eedcbfb9a6ff..66fa20476d0e 100644
> --- a/arch/powerpc/include/asm/processor.h
> +++ b/arch/powerpc/include/asm/processor.h
> @@ -429,6 +429,23 @@ extern void power4_idle_nap(void);
>  extern unsigned long cpuidle_disable;
>  enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
> 
> +#define STOP_ENABLE		0x00000001
> +
> +#define STOP_VERSION_P9       0x1
> +
> +/*
> + * Classify the dependencies of the stop states
> + * @idle_stop: function handler to handle the quirk stop version
> + * @cpuidle_prop: Signify support for stop states through kernel and/or firmware
> + * @stop_version: Classify quirk versions for stop states
> + */
> +typedef struct {
> +	unsigned long (*idle_stop)(unsigned long psscr, bool mmu_on);
> +	uint8_t cpuidle_prop;
> +	uint8_t stop_version;
> +} stop_deps_t;
> +extern stop_deps_t stop_dep;
> +
>  extern int powersave_nap;	/* set if nap mode can be used in idle loop */
> 
>  extern void power7_idle_type(unsigned long type);
> diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
> index 182b4047c1ef..db1a525e090d 100644
> --- a/arch/powerpc/kernel/dt_cpu_ftrs.c
> +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
> @@ -292,6 +292,8 @@ static int __init feat_enable_idle_stop(struct dt_cpu_feature *f)
>  	lpcr |=  LPCR_PECE1;
>  	lpcr |=  LPCR_PECE2;
>  	mtspr(SPRN_LPCR, lpcr);
> +	stop_dep.cpuidle_prop |= STOP_ENABLE;
> +	stop_dep.stop_version = STOP_VERSION_P9;
> 
>  	return 1;
>  }
> @@ -657,6 +659,9 @@ static void __init cpufeatures_setup_start(u32 isa)
>  	}
>  }
> 
> +stop_deps_t stop_dep = {NULL, 0x0, 0x0};
> +EXPORT_SYMBOL(stop_dep);
> +
>  static bool __init cpufeatures_process_feature(struct dt_cpu_feature *f)
>  {
>  	const struct dt_cpu_feature_match *m;
> diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> index 1841027b25c5..538f0842ac3f 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -842,7 +842,7 @@ static unsigned long power9_offline_stop(unsigned long psscr)
> 
>  #ifndef CONFIG_KVM_BOOK3S_HV_POSSIBLE
>  	__ppc64_runlatch_off();
> -	srr1 = power9_idle_stop(psscr, true);
> +	srr1 = stop_dep.idle_stop(psscr, true);
>  	__ppc64_runlatch_on();
>  #else
>  	/*
> @@ -858,7 +858,7 @@ static unsigned long power9_offline_stop(unsigned long psscr)
>  	local_paca->kvm_hstate.hwthread_state = KVM_HWTHREAD_IN_IDLE;
> 
>  	__ppc64_runlatch_off();
> -	srr1 = power9_idle_stop(psscr, false);
> +	srr1 = stop_dep.idle_stop(psscr, true);
>  	__ppc64_runlatch_on();
> 
>  	local_paca->kvm_hstate.hwthread_state = KVM_HWTHREAD_IN_KERNEL;
> @@ -886,7 +886,7 @@ void power9_idle_type(unsigned long stop_psscr_val,
>  	psscr = (psscr & ~stop_psscr_mask) | stop_psscr_val;
> 
>  	__ppc64_runlatch_off();
> -	srr1 = power9_idle_stop(psscr, true);
> +	srr1 = stop_dep.idle_stop(psscr, true);
>  	__ppc64_runlatch_on();
> 
>  	fini_irq_for_idle_irqsoff();
> @@ -1390,8 +1390,18 @@ static int __init pnv_init_idle_states(void)
>  	nr_pnv_idle_states = 0;
>  	supported_cpuidle_states = 0;
> 
> -	if (cpuidle_disable != IDLE_NO_OVERRIDE)
> +	if (cpuidle_disable != IDLE_NO_OVERRIDE ||
> +	    !(stop_dep.cpuidle_prop & STOP_ENABLE))
>  		goto out;
> +
> +	/* Check for supported version in kernel */
> +	if (stop_dep.stop_version & STOP_VERSION_P9) {
> +		stop_dep.idle_stop = power9_idle_stop;
> +	} else {
> +		stop_dep.idle_stop = NULL;
> +		goto out;
> +	}
> +
>  	rc = pnv_parse_cpuidle_dt();
>  	if (rc)
>  		return rc;
> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> index 1b299e801f74..7430a8edf5c9 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -371,7 +371,8 @@ static int powernv_add_idle_states(void)
>   */
>  static int powernv_idle_probe(void)
>  {
> -	if (cpuidle_disable != IDLE_NO_OVERRIDE)
> +	if (cpuidle_disable != IDLE_NO_OVERRIDE ||
> +	    !(stop_dep.cpuidle_prop & STOP_ENABLE))
>  		return -ENODEV;
> 
>  	if (firmware_has_feature(FW_FEATURE_OPAL)) {
> -- 
> 2.17.1
>