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SubjectRe: [RFC 3/3] Introduce capability for firmware-enabled-stop
Hi Pratik,

On Wed, Mar 04, 2020 at 09:31:23PM +0530, Pratik Rajesh Sampat wrote:
> Design patch that 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.
>
> The commit does not contain calling into the firmware to utilize
> firmware enabled stop.
>
> Signed-off-by: Pratik Rajesh Sampat <psampat at linux.ibm.com>
> ---
> arch/powerpc/include/asm/processor.h | 1 +
> arch/powerpc/kernel/dt_cpu_ftrs.c | 9 +++++++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
> index 277dbabafd02..978fab35d133 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


This could be made a bit in the "version" variable.

>
> #define STOP_VERSION_P9 0x1
> #define STOP_VERSION_P9_V1 0x2
> diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
> index 63e30aa49356..e00f8afabc46 100644
> --- a/arch/powerpc/kernel/dt_cpu_ftrs.c
> +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
> @@ -313,6 +313,14 @@ static int __init feat_enable_idle_stop_quirk(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;

stop_dep.cpuidle_version |= FIRMWARE_STOP_V1; or some such
variant.


> +
> + return 1;
> +}
> +
> static int __init feat_enable_mmu_hash(struct dt_cpu_feature *f)
> {
> u64 lpcr;
> @@ -608,6 +616,7 @@ static struct dt_cpu_feature_match __initdata
> {"alignment-interrupt-dsisr", feat_enable_align_dsisr, 0},
> {"idle-stop", feat_enable_idle_stop, 0},
> {"idle-stop-v1", feat_enable_idle_stop_quirk, 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},
> --
> 2.24.1
>

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