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Introduce offload_usage and corresponding apis to track offload usage on each USB device. Offload denotes that there is another co-processor accessing the USB device via the same USB host controller. To optimize power usage, it's essential to monitor whether the USB device is actively used by other co-processor. This information is vital when determining if a USB device can be safely suspended during system power state transitions. Signed-off-by: Guan-Yu Lin <guanyulin@google.com> Link: https://lore.kernel.org/r/20250911142051.90822-3-guanyulin@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: https://lore.kernel.org/r/20250911142051.90822-3-guanyulin@google.com
136 lines
3.4 KiB
C
136 lines
3.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* offload.c - USB offload related functions
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*
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* Copyright (c) 2025, Google LLC.
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*
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* Author: Guan-Yu Lin
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*/
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#include <linux/usb.h>
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#include "usb.h"
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/**
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* usb_offload_get - increment the offload_usage of a USB device
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* @udev: the USB device to increment its offload_usage
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*
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* Incrementing the offload_usage of a usb_device indicates that offload is
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* enabled on this usb_device; that is, another entity is actively handling USB
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* transfers. This information allows the USB driver to adjust its power
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* management policy based on offload activity.
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*
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* Return: 0 on success. A negative error code otherwise.
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*/
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int usb_offload_get(struct usb_device *udev)
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{
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int ret;
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usb_lock_device(udev);
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if (udev->state == USB_STATE_NOTATTACHED) {
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usb_unlock_device(udev);
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return -ENODEV;
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}
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if (udev->state == USB_STATE_SUSPENDED ||
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udev->offload_at_suspend) {
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usb_unlock_device(udev);
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return -EBUSY;
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}
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/*
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* offload_usage could only be modified when the device is active, since
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* it will alter the suspend flow of the device.
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*/
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ret = usb_autoresume_device(udev);
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if (ret < 0) {
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usb_unlock_device(udev);
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return ret;
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}
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udev->offload_usage++;
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usb_autosuspend_device(udev);
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usb_unlock_device(udev);
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return ret;
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}
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EXPORT_SYMBOL_GPL(usb_offload_get);
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/**
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* usb_offload_put - drop the offload_usage of a USB device
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* @udev: the USB device to drop its offload_usage
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*
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* The inverse operation of usb_offload_get, which drops the offload_usage of
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* a USB device. This information allows the USB driver to adjust its power
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* management policy based on offload activity.
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*
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* Return: 0 on success. A negative error code otherwise.
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*/
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int usb_offload_put(struct usb_device *udev)
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{
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int ret;
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usb_lock_device(udev);
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if (udev->state == USB_STATE_NOTATTACHED) {
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usb_unlock_device(udev);
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return -ENODEV;
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}
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if (udev->state == USB_STATE_SUSPENDED ||
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udev->offload_at_suspend) {
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usb_unlock_device(udev);
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return -EBUSY;
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}
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/*
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* offload_usage could only be modified when the device is active, since
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* it will alter the suspend flow of the device.
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*/
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ret = usb_autoresume_device(udev);
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if (ret < 0) {
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usb_unlock_device(udev);
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return ret;
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}
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/* Drop the count when it wasn't 0, ignore the operation otherwise. */
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if (udev->offload_usage)
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udev->offload_usage--;
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usb_autosuspend_device(udev);
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usb_unlock_device(udev);
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return ret;
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}
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EXPORT_SYMBOL_GPL(usb_offload_put);
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/**
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* usb_offload_check - check offload activities on a USB device
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* @udev: the USB device to check its offload activity.
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*
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* Check if there are any offload activity on the USB device right now. This
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* information could be used for power management or other forms of resource
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* management.
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*
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* The caller must hold @udev's device lock. In addition, the caller should
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* ensure downstream usb devices are all either suspended or marked as
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* "offload_at_suspend" to ensure the correctness of the return value.
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*
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* Returns true on any offload activity, false otherwise.
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*/
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bool usb_offload_check(struct usb_device *udev) __must_hold(&udev->dev->mutex)
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{
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struct usb_device *child;
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bool active;
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int port1;
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usb_hub_for_each_child(udev, port1, child) {
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usb_lock_device(child);
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active = usb_offload_check(child);
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usb_unlock_device(child);
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if (active)
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return true;
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}
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return !!udev->offload_usage;
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}
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EXPORT_SYMBOL_GPL(usb_offload_check);
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