[Skiboot] [RFC 2/2] opal : Introducing capability for firmware-stop-support

[Gautham R Shenoy]

Hello Abhishek,

On Sun, Apr 26, 2020 at 08:17:03PM -0500, Abhishek Goel wrote:
> This patch introduces support for firmware-stop-support. If Kernel does
> not know about stop version, it can fallback to opal for idle stop
> support if firmware-stop-supported property is present.
> 
> Just like "idle-stop", "idle-stop-quirk" can be defined in features if
> there is some quirk that needs to be handled and if kernel identifies
> the corresponding version it can use that or fallback to opal for idle
> stop support.
> 
> The complete idea was previosuly posted in this patch:
> https://patchwork.ozlabs.org/project/skiboot/list/?series=162400
> 
> Signed-off-by: Pratik Rajesh Sampat <psampat at linux.ibm.com>
> Signed-off-by: Abhishek Goel <huntbag at linux.vnet.ibm.com>
> ---
> 
>  v1->v2 : This patch has been newly added in this series.
> 
>  core/cpufeatures.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/core/cpufeatures.c b/core/cpufeatures.c
> index c6754abb..1f516028 100644
> --- a/core/cpufeatures.c
> +++ b/core/cpufeatures.c
> @@ -510,6 +510,19 @@ static const struct cpu_feature cpu_features_table[] = {
>  	-1, -1, -1,
>  	NULL, },
> 
> +	/*
> +	 * ISAv3.0B firmware-stop-support
> +	 * Opal fallback for shallow stop states
> +	 */
> +#ifdef HAVE_BIG_ENDIAN
> +	{ "firmware-stop-supported",


In this patchset, you are supporting only the non-hypervisor
loss stop states (stop0, stop1, stop2) only in the opal
cpuidle-driver. Is the string "firmware-stop-supported" intended for
only that ? In that case it should be documented, so that in the
presence of this feature, should the kernel choose to opt for opal
cpuidle-driver, it will select only shallow states.




> +	CPU_P9,
> +	ISA_V3_0B, USABLE_HV|USABLE_OS,
> +	HV_CUSTOM, OS_CUSTOM,
> +	-1, -1, -1,
> +	NULL, },
> +#endif
> +
>  	/*
>  	 * ISAv3.0B Hypervisor Virtualization Interrupt
>  	 * Also associated system registers, LPCR EE, HEIC, HVICE,
> -- 
> 2.17.1
>