Re: [PATCH v14 5/9] platform/x86: asus-armoury: add core count control

["Mario Limonciello (AMD) (kernel.org)" <superm1@kernel.org>]

On 10/20/2025 12:37 PM, Denis Benato wrote:
> 
> On 10/20/25 19:15, Ilpo Järvinen wrote:
>> On Sat, 18 Oct 2025, Denis Benato wrote:
>>> On 10/17/25 14:48, Ilpo Järvinen wrote:
>>>> On Wed, 15 Oct 2025, Denis Benato wrote:
>>>>
>>>>> From: "Luke D. Jones" <luke@ljones.dev>
>>>>>
>>>>> Implement Intel core enablement under the asus-armoury module using the
>>>>> fw_attributes class.
>>>>>
>>>>> This allows users to enable or disable preformance or efficiency cores
>>>>> depending on their requirements. After change a reboot is required.
>>>>>
>>>>> Signed-off-by: Denis Benato <benato.denis96@gmail.com>
>>>>> Signed-off-by: Luke D. Jones <luke@ljones.dev>
>>>>> ---
>>>>>   drivers/platform/x86/asus-armoury.c        | 258 ++++++++++++++++++++-
>>>>>   drivers/platform/x86/asus-armoury.h        |  28 +++
>>>>>   include/linux/platform_data/x86/asus-wmi.h |   5 +
>>>>>   3 files changed, 290 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/platform/x86/asus-armoury.c b/drivers/platform/x86/asus-armoury.c
>>>>> index 3b49a27e397d..3d963025d84e 100644
>>>>> --- a/drivers/platform/x86/asus-armoury.c
>>>>> +++ b/drivers/platform/x86/asus-armoury.c
>>>>> +static ssize_t cores_value_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf,
>>>>> +				enum cpu_core_type core_type, enum cpu_core_value core_value)
>>>>> +{
>>>>> +	u32 cores;
>>>>> +
>>>>> +	switch (core_value) {
>>>>> +	case CPU_CORE_DEFAULT:
>>>>> +	case CPU_CORE_MAX:
>>>>> +		if (core_type == CPU_CORE_PERF)
>>>>> +			return sysfs_emit(buf, "%u\n",
>>>>> +					  asus_armoury.cpu_cores->max_perf_cores);
>>>>> +		else
>>>>> +			return sysfs_emit(buf, "%u\n",
>>>>> +					  asus_armoury.cpu_cores->max_power_cores);
>>>>> +	case CPU_CORE_MIN:
>>>>> +		if (core_type == CPU_CORE_PERF)
>>>>> +			return sysfs_emit(buf, "%u\n",
>>>>> +					  asus_armoury.cpu_cores->min_perf_cores);
>>>>> +		else
>>>>> +			return sysfs_emit(buf, "%u\n",
>>>>> +					  asus_armoury.cpu_cores->min_power_cores);
>>>>> +	default:
>>>>> +		break;
>>>>> +	}
>>>>> +
>>>>> +	if (core_type == CPU_CORE_PERF)
>>>>> +		cores = asus_armoury.cpu_cores->cur_perf_cores;
>>>>> +	else
>>>>> +		cores = asus_armoury.cpu_cores->cur_power_cores;
>>>> Why isn't this inside the switch?? The logic in this function looks very
>>>> mixed up.
>>>>
>>>> If I'd be you, I'd consider converting the asus_armoury.cpu_cores to a
>>>> multi-dimensional array. It would make this just bounds checks and one
>>>> line to get the data.
>>> Please note that this interface has the potential to brick in an irreversible
>>> way laptops and it has happened.
>> This function only prints values held by kernel in its internal storage?
>> How can that brick something?
>>
>>> Of all the code CPU core handling it the most delicate code of all since
>>> a wrong value here means permanent irreversible damage.
>>>
>>> I am more than happy making changes that can be easily verified,
>>> but others more complex changes will put (at least) my own hardware
>>> at risk.
>> Understood.
>>
>>> If you think benefit outweighs risks I will try my best.
>>>>> +	return sysfs_emit(buf, "%u\n", cores);
>>>>> +}
>>>>> +
>>>>> +static ssize_t cores_current_value_store(struct kobject *kobj, struct kobj_attribute *attr,
>>>>> +					 const char *buf, enum cpu_core_type core_type)
>>>>> +{
>>>>> +	u32 new_cores, perf_cores, power_cores, out_val, min, max;
>>>>> +	int result, err;
>>>>> +
>>>>> +	result = kstrtou32(buf, 10, &new_cores);
>>>>> +	if (result)
>>>>> +		return result;
>>>>> +
>>>>> +	scoped_guard(mutex, &asus_armoury.cpu_core_mutex) {
>>>>> +		if (core_type == CPU_CORE_PERF) {
>>>>> +			perf_cores = new_cores;
>>>>> +			power_cores = asus_armoury.cpu_cores->cur_power_cores;
>>>>> +			min = asus_armoury.cpu_cores->min_perf_cores;
>>>>> +			max = asus_armoury.cpu_cores->max_perf_cores;
>>>>> +		} else {
>>>>> +			perf_cores = asus_armoury.cpu_cores->cur_perf_cores;
>>>>> +			power_cores = new_cores;
>>>>> +			min = asus_armoury.cpu_cores->min_power_cores;
>>>>> +			max = asus_armoury.cpu_cores->max_power_cores;
>>>>> +		}
>>>>> +
>>>>> +		if (new_cores < min || new_cores > max)
>>>>> +			return -EINVAL;
>>>>> +
>>>>> +		out_val = FIELD_PREP(ASUS_PERF_CORE_MASK, perf_cores) |
>>>>> +			FIELD_PREP(ASUS_POWER_CORE_MASK, power_cores);
>>>>> +
>>>>> +		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_CORES, out_val, &result);
>>>>> +		if (err) {
>>>>> +			pr_warn("Failed to set CPU core count: %d\n", err);
>>>>> +			return err;
>>>>> +		}
>>>>> +
>>>>> +		if (result > 1) {
>>>>> +			pr_warn("Failed to set CPU core count (result): 0x%x\n", result);
>>>>> +			return -EIO;
>>>>> +		}
>>>>> +	}
>>>>> +
>>>>> +	pr_info("CPU core count changed, reboot required\n");
>>>> This interface has a problematic behavior. If user wants to adjust both
>>>> core counts one after another (without reboot in between), the new value
>>>> of the first core count will be overwritten on the second store.
>>>>
>>>> You might have to store also the value that will be used after the next
>>>> boot to solve it but how the divergence should be presented to user is
>>>> another question to which I don't have a good answer.
>>> Given what I have written above I am thinking more along the lines of allowing
>>> only one change at the time, giving absolute priority to the ability to demonstrate
>>> not all P-cores can be disabled all at once, or after a reboot hardware will be
>>> irreversibly lost. It cannot be recovered the same way as I did with APU mem.
>>>
>>> To summarize I am more inclined in allowing only small changes,
>>> or to postpone this patch entirely while we think to a better, safer solution.
>> Fair enough, please mention this as in the changelog as a justification
>> and to warn other messing with the code.
>>
>>>> This seems a more general problem, that is, how to represent values which
>>>> are only enacted after booting (current vs to-be-current) as it doesn't
>>>> fit to the current, min, max, possible_values, type model.
>>>>
>>> Enabling eGPU on a laptop with a dGPU that is active makes the PCI-e
>>> spam PCI AER uncorrectable errors and renders both GPUs unusable.
>>>
>>> I have gone with storing the value at driver load time and treating it
>>> as the boot value for 2/9 (eGPU), but I am very open to suggestions!
>> I'm not entirely sure what you're trying to say here. My point is that
>> there's no way for user to know what value something will be changed to
>> (the "to-be-current" value) except through rebooting the system (when the
>> "to-be-current" value becomes the "current").
>>
> Users do know what the value will be changed to because that is what the
> WMI interface will tell: the issue is in reverse (knowing what settings were
> applied when booting the laptop): one has to infer those looking at
> the current state of things.
> 
> For example it is only possible to know if the next boot will have
> sound or not, not if a sound was emitted at the current boot.
> 
> I haven't seen examples of devstates not returning the future value,
> but I do have seen my ally returning dGPU property presence when
> there is no dGPU in it and it appears to be a no-op, so I had to remove
> (or rather avoid adding) a safeguard against possible PCI bus conflicts
> that I had planned.
> 
> Thanks,
> 
> Denis
> 

There is a concept in the firmware attributes spec 
(sysfs-class-firmware-attributes) for "pending_reboot".

I think setting this to 1 should indicate there are changes that will 
happen on next boot.