On Sun, Apr 26, 2020 at 09:10:27PM -0500, Abhishek Goel wrote:
> This patch introduces the capability for firmware to handle the stop
> states instead. A bit is set based on the discovery of the feature
> and correspondingly also the responsibility to handle the stop states.
>
> If Kernel does not know about stop version, it can fallback to opal for
> idle stop support if firmware-stop-supported property is present.
>
> Earlier this patch was posted as part of this series :
> https://lkml.org/lkml/2020/3/4/589
>
> Signed-off-by: Pratik Rajesh Sampat <psam...@linux.ibm.com>
> Signed-off-by: Abhishek Goel <hunt...@linux.vnet.ibm.com>
> ---
>
> v1->v2: This patch is newly added in this series.
>
> arch/powerpc/include/asm/processor.h | 1 +
> arch/powerpc/kernel/dt_cpu_ftrs.c | 8 ++++++++
> arch/powerpc/platforms/powernv/idle.c | 27 ++++++++++++++++-----------
> 3 files changed, 25 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/processor.h
> b/arch/powerpc/include/asm/processor.h
> index 66fa20476d0e..d5c6532b11ef 100644
> --- a/arch/powerpc/include/asm/processor.h
> +++ b/arch/powerpc/include/asm/processor.h
> @@ -430,6 +430,7 @@ extern unsigned long cpuidle_disable;
> enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF};
>
> #define STOP_ENABLE 0x00000001
> +#define FIRMWARE_STOP_ENABLE 0x00000010
>
> #define STOP_VERSION_P9 0x1
>
> diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c
> b/arch/powerpc/kernel/dt_cpu_ftrs.c
> index db1a525e090d..ff4a87b79702 100644
> --- a/arch/powerpc/kernel/dt_cpu_ftrs.c
> +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
> @@ -298,6 +298,13 @@ static int __init feat_enable_idle_stop(struct
> dt_cpu_feature *f)
> return 1;
> }
>
> +static int __init feat_enable_firmware_stop(struct dt_cpu_feature *f)
> +{
> + stop_dep.cpuidle_prop |= FIRMWARE_STOP_ENABLE;
> +
> + return 1;
> +}
> +
> static int __init feat_enable_mmu_hash(struct dt_cpu_feature *f)
> {
> u64 lpcr;
> @@ -592,6 +599,7 @@ static struct dt_cpu_feature_match __initdata
> {"idle-nap", feat_enable_idle_nap, 0},
> {"alignment-interrupt-dsisr", feat_enable_align_dsisr, 0},
> {"idle-stop", feat_enable_idle_stop, 0},
> + {"firmware-stop-supported", feat_enable_firmware_stop, 0},
> {"machine-check-power8", feat_enable_mce_power8, 0},
> {"performance-monitor-power8", feat_enable_pmu_power8, 0},
> {"data-stream-control-register", feat_enable_dscr, CPU_FTR_DSCR},
> diff --git a/arch/powerpc/platforms/powernv/idle.c
> b/arch/powerpc/platforms/powernv/idle.c
> index 538f0842ac3f..0de5de81902e 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -633,16 +633,6 @@ static unsigned long power9_idle_stop(unsigned long
> psscr, bool mmu_on)
> unsigned long mmcr0 = 0;
> struct p9_sprs sprs = {}; /* avoid false used-uninitialised */
> bool sprs_saved = false;
> - int rc = 0;
> -
> - /*
> - * Kernel takes decision whether to make OPAL call or not. This logic
> - * will be combined with the logic for BE opal to take decision.
> - */
> - if (firmware_stop_supported) {
> - rc = opal_cpu_idle(cpu_to_be64(__pa(&srr1)), (uint64_t) psscr);
> - goto out;
> - }
>
> if (!(psscr & (PSSCR_EC|PSSCR_ESL))) {
> /* EC=ESL=0 case */
> @@ -835,6 +825,19 @@ static unsigned long power9_idle_stop(unsigned long
> psscr, bool mmu_on)
> return srr1;
> }
>
> +static unsigned long power9_firmware_idle_stop(unsigned long psscr, bool
> mmu_on)
> +{
> + unsigned long srr1;
> + int rc;
> +
> + rc = opal_cpu_idle(cpu_to_be64(__pa(&srr1)), (uint64_t) psscr);
> +
> + if (mmu_on)
> + mtmsr(MSR_KERNEL);
> + return srr1;
> +
> +}
> +
> #ifdef CONFIG_HOTPLUG_CPU
> static unsigned long power9_offline_stop(unsigned long psscr)
> {
> @@ -1394,9 +1397,11 @@ static int __init pnv_init_idle_states(void)
> !(stop_dep.cpuidle_prop & STOP_ENABLE))
> goto out;
>
> - /* Check for supported version in kernel */
> + /* Check for supported version in kernel or fallback to kernel*/
> if (stop_dep.stop_version & STOP_VERSION_P9) {
> stop_dep.idle_stop = power9_idle_stop;
> + } else if (stop_dep.cpuidle_prop & FIRMWARE_STOP_ENABLE) {
> + stop_dep.idle_stop = power9_firmware_idle_stop;
Ok, so in this patch you first check if the "idle-stop" feature is
available. Only otherwise you fallback to the OPAL based cpuidle
driver.
This looks ok to me.
> } else {
> stop_dep.idle_stop = NULL;
> goto out;
> --
> 2.17.1
>
--
Thanks and Regards
gautham.
