Merge patch series "Support system sleep with offloaded usb transfers" into usb-next

Merge patch series "Support system sleep with offloaded usb transfers" into usb-next

Guan-Yu Lin <guanyulin@google.com> says:

Wesley Cheng and Mathias Nyman's USB offload design enables a
co-processor to handle some USB transfers, potentially allowing the
system to sleep (suspend-to-RAM) and save power. However, Linux's System
Sleep model halts the USB host controller when the main system isn't
managing any USB transfers. To address this, the proposal modifies the
system to recognize offloaded USB transfers and manage power
accordingly. This way, offloaded USB transfers could still happen during
system sleep (Suspend-to-RAM).

This involves two key steps:
1. Transfer Status Tracking: Propose offload_usage and corresponding
   apis drivers could track USB transfers on the co-processor, ensuring
   the system is aware of any ongoing activity.
2. Power Management Adjustment:  Modifications to the USB driver stack
   (xhci host controller driver, and USB device drivers) allow the
   system to sleep (Suspend-to-RAM) without disrupting co-processor
   managed USB transfers. This involves adding conditional checks to
   bypass some power management operations in the System Sleep model.

Link: https://lore.kernel.org/r/20250911142051.90822-1-guanyulin@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>