Re: [PATCH v4 0/2] usb: offload: Decouple interrupter lifecycle and refactor usage tracking

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 4/1/26 16:38, Greg KH wrote:
> On Wed, Apr 01, 2026 at 12:32:16PM +0000, Guan-Yu Lin wrote:
>> The current USB offload implementation couples the allocation of xHCI
>> sideband interrupters with the device's offload usage counter. This
>> coupling is conceptually incorrect, as hardware resource availability
>> and power management state serve distinct purposes.
>>
>> Furthermore, the reliance on the coarse USB device lock for offload
>> state updates has led to potential recursive locking issues,
>> especially during device disconnect when the lock is already held
>> by the USB core.
>>
>> This series refactors the offload synchronization by introducing a
>> dedicated spinlock for offload state, allowing for more granular
>> concurrency control and avoiding deadlocks. It also optimizes power
>> management by ensuring that offload state is only modified when the
>> device is already active, avoiding unnecessary auto-resumes.
>>
>> Patch 1 introduces the `offload_lock` spinlock and `offload_pm_locked`
>> synchronization, replacing the coarse `udev->lock` and the legacy
>> `offload_at_suspend` flag. It also updates `usb_offload_get/put` to use
>> `pm_runtime_get_if_active()`.
>>
>> Patch 2 removes the implicit usage tracking from the xHCI sideband layer
>> and delegates the responsibility to class drivers, who have the
>> correct context for managing offload data stream activity.
> 
> Ok, this looks much better, thanks for the revisions.
> 
> If the xhci maintainer acks these, I'll be glad to apply them to my
> tree.

For both patches:

Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>