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

[Abhishek]

Hi Gautham,


On 04/27/2020 03:06 PM, Gautham R Shenoy wrote:
> 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.
>
>
>
As of now, it is intended for only shallow states.
Will include documentation  for it in next iteration.

Thanks,
Abhishek