[RFC PATCH 24/36] arm_mpam: Extend reset logic to allow devices to be reset any time

[James Morse]

Hi Ben,

On 28/07/2025 11:22, Ben Horgan wrote:
> On 7/11/25 19:36, James Morse wrote:
>> cpuhp callbacks aren't the only time the MSC configuration may need to
>> be reset. Resctrl has an API call to reset a class.
>> If an MPAM error interrupt arrives it indicates the driver has
>> misprogrammed an MSC. The safest thing to do is reset all the MSCs
>> and disable MPAM.
>>
>> Add a helper to reset RIS via their class. Call this from mpam_disable(),
>> which can be scheduled from the error interrupt handler.
>> diff --git a/drivers/platform/arm64/mpam/mpam_devices.c b/drivers/platform/arm64/mpam/
>> mpam_devices.c
>> index 2e32e54cc081..145535cd4732 100644
>> --- a/drivers/platform/arm64/mpam/mpam_devices.c
>> +++ b/drivers/platform/arm64/mpam/mpam_devices.c

>> +/*
>> + * Called in response to an error IRQ.
>> + * All of MPAMs errors indicate a software bug, restore any modified
>> + * controls to their reset values.
>> + */
>> +void mpam_disable(void)
>> +{
>> +    int idx;
>> +    struct mpam_class *class;
>> +
>> +    idx = srcu_read_lock(&mpam_srcu);
>> +    list_for_each_entry_srcu(class, &mpam_classes, classes_list,
>> +                 srcu_read_lock_held(&mpam_srcu))
>> +        mpam_reset_class(class);
>> +    srcu_read_unlock(&mpam_srcu, idx);
>> +}
> Consider moving to the next patch where you introduce interrupt support.

I pulled these changes out of that patch to try and make it simpler!
Doing that would leave a bunch of static functions unused.


Thanks,

James