[RFC] Support stop state version quirk and firmware enabled stop

[RFC] Support stop state version quirk and firmware enabled stop

[Pratik Rajesh Sampat]

A concept patch in Skiboot to illustrate the case wherein handling of
stop states for different DD versions of a CPU can be achieved by a
simple modification in the list of cpu_features.
As an example idle-stop1 is defined which uses P9_CPU_DD1 to define the
cpu feature.

Along with that, an implementation is being worked upon the LE OPAL
series which helps OPAL handle the stop state entry and exit.

This patch advertises this capability of the firmware which can be
availed if the quirk-version-setting is not cognizable.

The firmware-enabled stop is being worked by Abhishek Goel
<huntbag@linux.vnet.ibm.com> building upon the LE OPAL series.

Signed-off-by: Pratik Rajesh Sampat <psampat@linux.ibm.com>
---
 core/cpufeatures.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/core/cpufeatures.c b/core/cpufeatures.c
index ec30c975..b9875e7b 100644
--- a/core/cpufeatures.c
+++ b/core/cpufeatures.c
@@ -510,6 +510,25 @@ static const struct cpu_feature cpu_features_table[] = {
 	-1, -1, -1,
 	NULL, },
 
+	/*
+	 * QUIRK for ISAv3.0B stop idle instructions and registers
+	 * Helps us determine if there are any quirks
+	 * XXX: Same of idle-stop
+	 */
+	{ "idle-stop-v1",
+	CPU_P9_DD1,
+	ISA_V3_0B, USABLE_HV|USABLE_OS,
+	HV_CUSTOM, OS_CUSTOM,
+	-1, -1, -1,
+	NULL, },
+
+	{ "firmware-stop-supported",
+	CPU_P9,
+	ISA_V3_0B, USABLE_HV|USABLE_OS,
+	HV_CUSTOM, OS_CUSTOM,
+	-1, -1, -1,
+	NULL, },
+
 	/*
 	 * ISAv3.0B Hypervisor Virtualization Interrupt
 	 * Also associated system registers, LPCR EE, HEIC, HVICE,
@@ -883,6 +902,9 @@ static void add_cpufeatures(struct dt_node *cpus,
 		const struct cpu_feature *f = &cpu_features_table[i];
 
 		if (f->cpus_supported & cpu_feature_cpu) {
+			if (!strcmp(f->name, "firmware-stop-supported") &&
+			    HAVE_BIG_ENDIAN)
+				continue;
 			DBG("  '%s'\n", f->name);
 			add_cpu_feature_nodeps(features, f);
 		}
-- 
2.24.1

Re: [RFC] Support stop state version quirk and firmware enabled stop

[Gautham R Shenoy]

Hi Pratik,

On Wed, Mar 04, 2020 at 09:26:48PM +0530, Pratik Rajesh Sampat wrote:
> A concept patch in Skiboot to illustrate the case wherein handling of
> stop states for different DD versions of a CPU can be achieved by a
> simple modification in the list of cpu_features.
> As an example idle-stop1 is defined which uses P9_CPU_DD1 to define the
> cpu feature.
> 
> Along with that, an implementation is being worked upon the LE OPAL
> series which helps OPAL handle the stop state entry and exit.
> 
> This patch advertises this capability of the firmware which can be
> availed if the quirk-version-setting is not cognizable.
> 
> The firmware-enabled stop is being worked by Abhishek Goel
> <huntbag@linux.vnet.ibm.com> building upon the LE OPAL series.
> 
> Signed-off-by: Pratik Rajesh Sampat <psampat@linux.ibm.com>
> ---
>  core/cpufeatures.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/core/cpufeatures.c b/core/cpufeatures.c
> index ec30c975..b9875e7b 100644
> --- a/core/cpufeatures.c
> +++ b/core/cpufeatures.c
> @@ -510,6 +510,25 @@ static const struct cpu_feature cpu_features_table[] = {
>  	-1, -1, -1,
>  	NULL, },
> 
> +	/*
> +	 * QUIRK for ISAv3.0B stop idle instructions and registers
> +	 * Helps us determine if there are any quirks
> +	 * XXX: Same of idle-stop
> +	 */
> +	{ "idle-stop-v1",
> +	CPU_P9_DD1,
> +	ISA_V3_0B, USABLE_HV|USABLE_OS,
> +	HV_CUSTOM, OS_CUSTOM,
> +	-1, -1, -1,
> +	NULL, },


So, at this point, we don't need any such quirk for any of the DD
version right ? This is to demonstrate that if say P9_DD1 had a quirk
w.r.t stop-state handling, then this is how we would advertise it to
the kernel.

> +
> +	{ "firmware-stop-supported",
> +	CPU_P9,
> +	ISA_V3_0B, USABLE_HV|USABLE_OS,
> +	HV_CUSTOM, OS_CUSTOM,
> +	-1, -1, -1,
> +	NULL, },
> +


I suppose this is for the opal-cpuidle driver support posted here:
https://lists.ozlabs.org/pipermail/skiboot/2020-April/016726.html

>  	/*
>  	 * ISAv3.0B Hypervisor Virtualization Interrupt
>  	 * Also associated system registers, LPCR EE, HEIC, HVICE,
> @@ -883,6 +902,9 @@ static void add_cpufeatures(struct dt_node *cpus,
>  		const struct cpu_feature *f = &cpu_features_table[i];
> 
>  		if (f->cpus_supported & cpu_feature_cpu) {
> +			if (!strcmp(f->name, "firmware-stop-supported") &&
> +			    HAVE_BIG_ENDIAN)
> +				continue;

In OPAL do we have an macro defining BIG_ENDIAN ? If yes, you could
wrap the "firmware-stop-supported" in cpu_features_table[] within
#ifndef BIG_ENDIAN. That way you won't need a special case here.



>  			DBG("  '%s'\n", f->name);
>  			add_cpu_feature_nodeps(features, f);
>  		}
> -- 
> 2.24.1
> 

--
Thanks and Regards
gautham.

Re: [RFC] Support stop state version quirk and firmware enabled stop

[Pratik Sampat]

Hello Gautham,

On 08/04/20 3:20 pm, Gautham R Shenoy wrote:
> Hi Pratik,
>
> On Wed, Mar 04, 2020 at 09:26:48PM +0530, Pratik Rajesh Sampat wrote:
>> A concept patch in Skiboot to illustrate the case wherein handling of
>> stop states for different DD versions of a CPU can be achieved by a
>> simple modification in the list of cpu_features.
>> As an example idle-stop1 is defined which uses P9_CPU_DD1 to define the
>> cpu feature.
>>
>> Along with that, an implementation is being worked upon the LE OPAL
>> series which helps OPAL handle the stop state entry and exit.
>>
>> This patch advertises this capability of the firmware which can be
>> availed if the quirk-version-setting is not cognizable.
>>
>> The firmware-enabled stop is being worked by Abhishek Goel
>> <huntbag@linux.vnet.ibm.com> building upon the LE OPAL series.
>>
>> Signed-off-by: Pratik Rajesh Sampat <psampat@linux.ibm.com>
>> ---
>>   core/cpufeatures.c | 22 ++++++++++++++++++++++
>>   1 file changed, 22 insertions(+)
>>
>> diff --git a/core/cpufeatures.c b/core/cpufeatures.c
>> index ec30c975..b9875e7b 100644
>> --- a/core/cpufeatures.c
>> +++ b/core/cpufeatures.c
>> @@ -510,6 +510,25 @@ static const struct cpu_feature cpu_features_table[] = {
>>   	-1, -1, -1,
>>   	NULL, },
>>
>> +	/*
>> +	 * QUIRK for ISAv3.0B stop idle instructions and registers
>> +	 * Helps us determine if there are any quirks
>> +	 * XXX: Same of idle-stop
>> +	 */
>> +	{ "idle-stop-v1",
>> +	CPU_P9_DD1,
>> +	ISA_V3_0B, USABLE_HV|USABLE_OS,
>> +	HV_CUSTOM, OS_CUSTOM,
>> +	-1, -1, -1,
>> +	NULL, },
>
> So, at this point, we don't need any such quirk for any of the DD
> version right ? This is to demonstrate that if say P9_DD1 had a quirk
> w.r.t stop-state handling, then this is how we would advertise it to
> the kernel.

Absolutely, A dummy property has been added to show how quirk handling
with stop-states.

>> +
>> +	{ "firmware-stop-supported",
>> +	CPU_P9,
>> +	ISA_V3_0B, USABLE_HV|USABLE_OS,
>> +	HV_CUSTOM, OS_CUSTOM,
>> +	-1, -1, -1,
>> +	NULL, },
>> +
>
> I suppose this is for the opal-cpuidle driver support posted here:
> https://lists.ozlabs.org/pipermail/skiboot/2020-April/016726.html

Right, this complements in usage of the opal-cpuidle driver

>>   	/*
>>   	 * ISAv3.0B Hypervisor Virtualization Interrupt
>>   	 * Also associated system registers, LPCR EE, HEIC, HVICE,
>> @@ -883,6 +902,9 @@ static void add_cpufeatures(struct dt_node *cpus,
>>   		const struct cpu_feature *f = &cpu_features_table[i];
>>
>>   		if (f->cpus_supported & cpu_feature_cpu) {
>> +			if (!strcmp(f->name, "firmware-stop-supported") &&
>> +			    HAVE_BIG_ENDIAN)
>> +				continue;
> In OPAL do we have an macro defining BIG_ENDIAN ? If yes, you could
> wrap the "firmware-stop-supported" in cpu_features_table[] within
> #ifndef BIG_ENDIAN. That way you won't need a special case here.
>
HAVE_BIG_ENDIAN is actually a macro. Its a good idea to wrap it in
the declaration itself.

>
>>   			DBG("  '%s'\n", f->name);
>>   			add_cpu_feature_nodeps(features, f);
>>   		}
>> -- 
>> 2.24.1
>>
> --
> Thanks and Regards
> gautham.