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Message-ID: <20250416144917.16822-5-guanyulin@google.com>
Date: Wed, 16 Apr 2025 14:43:04 +0000
From: Guan-Yu Lin <guanyulin@...gle.com>
To: gregkh@...uxfoundation.org, mathias.nyman@...el.com,
stern@...land.harvard.edu, sumit.garg@...nel.org, gargaditya08@...e.com,
kekrby@...il.com, jeff.johnson@....qualcomm.com, quic_zijuhu@...cinc.com,
andriy.shevchenko@...ux.intel.com, ben@...adent.org.uk, broonie@...nel.org,
quic_wcheng@...cinc.com
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
Guan-Yu Lin <guanyulin@...gle.com>
Subject: [PATCH v12 4/4] usb: host: enable USB offload during system sleep
Sharing a USB controller with another entity via xhci-sideband driver
creates power management complexities. To prevent the USB controller
from being inadvertently deactivated while in use by the other entity, a
usage-count based mechanism is implemented. This allows the system to
manage power effectively, ensuring the controller remains available
whenever needed.
In order to maintain full functionality of an offloaded USB devices,
several changes are made within the suspend flow of such devices:
- skip usb_suspend_device() so that the port/hub are still active for
USB transfers via offloaded path.
- not suspending the endpoints which are used by USB interfaces marked
with needs_remote_wakeup. Namely, skip usb_suspend_interface() and
usb_hcd_flush_endpoint() on associated USB interfaces. This reserves a
pending interrupt urb during system suspend for handling the interrupt
transfer, which is necessary since remote wakeup doesn't apply in the
offloaded USB devices when controller is still active.
- not flushing the endpoints of actively offloaded USB devices. Given
that the USB devices is used by another entity, unilaterally flush the
endpoint might lead to unexpected behavior on another entity.
- not suspending the xhci controller. This is done by skipping the
suspend/resume callbacks in the xhci platform driver.
Signed-off-by: Guan-Yu Lin <guanyulin@...gle.com>
---
drivers/usb/core/driver.c | 50 +++++++++++++++++++++++++++++++-----
drivers/usb/host/xhci-plat.c | 19 ++++++++++++++
drivers/usb/host/xhci-plat.h | 1 +
include/linux/usb.h | 7 ++---
4 files changed, 68 insertions(+), 9 deletions(-)
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 76372690add0..6c3eb8fb6310 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1420,11 +1420,28 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
udev->state == USB_STATE_SUSPENDED)
goto done;
+ if (msg.event == PM_EVENT_SUSPEND && usb_offload_check(udev)) {
+ dev_dbg(&udev->dev, "device offloaded, skip suspend.\n");
+ udev->offload_at_suspend = 1;
+ }
+
/* Suspend all the interfaces and then udev itself */
if (udev->actconfig) {
n = udev->actconfig->desc.bNumInterfaces;
for (i = n - 1; i >= 0; --i) {
intf = udev->actconfig->interface[i];
+ /*
+ * Don't suspend interfaces with remote wakeup while
+ * the controller is active. This preserves pending
+ * interrupt urbs, allowing interrupt events to be
+ * handled during system suspend.
+ */
+ if (udev->offload_at_suspend &&
+ intf->needs_remote_wakeup) {
+ dev_dbg(&intf->dev,
+ "device offloaded, skip suspend.\n");
+ continue;
+ }
status = usb_suspend_interface(udev, intf, msg);
/* Ignore errors during system sleep transitions */
@@ -1435,7 +1452,8 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
}
}
if (status == 0) {
- status = usb_suspend_device(udev, msg);
+ if (!udev->offload_at_suspend)
+ status = usb_suspend_device(udev, msg);
/*
* Ignore errors from non-root-hub devices during
@@ -1480,9 +1498,11 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
*/
} else {
udev->can_submit = 0;
- for (i = 0; i < 16; ++i) {
- usb_hcd_flush_endpoint(udev, udev->ep_out[i]);
- usb_hcd_flush_endpoint(udev, udev->ep_in[i]);
+ if (!udev->offload_at_suspend) {
+ for (i = 0; i < 16; ++i) {
+ usb_hcd_flush_endpoint(udev, udev->ep_out[i]);
+ usb_hcd_flush_endpoint(udev, udev->ep_in[i]);
+ }
}
}
@@ -1524,17 +1544,35 @@ static int usb_resume_both(struct usb_device *udev, pm_message_t msg)
udev->can_submit = 1;
/* Resume the device */
- if (udev->state == USB_STATE_SUSPENDED || udev->reset_resume)
- status = usb_resume_device(udev, msg);
+ if (udev->state == USB_STATE_SUSPENDED || udev->reset_resume) {
+ if (!udev->offload_at_suspend)
+ status = usb_resume_device(udev, msg);
+ else
+ dev_dbg(&udev->dev,
+ "device offloaded, skip resume.\n");
+ }
/* Resume the interfaces */
if (status == 0 && udev->actconfig) {
for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
intf = udev->actconfig->interface[i];
+ /*
+ * Interfaces with remote wakeup aren't suspended
+ * while the controller is active. This preserves
+ * pending interrupt urbs, allowing interrupt events
+ * to be handled during system suspend.
+ */
+ if (udev->offload_at_suspend &&
+ intf->needs_remote_wakeup) {
+ dev_dbg(&intf->dev,
+ "device offloaded, skip resume.\n");
+ continue;
+ }
usb_resume_interface(udev, intf, msg,
udev->reset_resume);
}
}
+ udev->offload_at_suspend = 0;
usb_mark_last_busy(udev);
done:
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index 9843d3ad5cf4..598f1b974347 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -20,6 +20,7 @@
#include <linux/acpi.h>
#include <linux/usb/of.h>
#include <linux/reset.h>
+#include <linux/usb/xhci-sideband.h>
#include "xhci.h"
#include "xhci-plat.h"
@@ -483,6 +484,15 @@ static int xhci_plat_suspend_common(struct device *dev)
static int xhci_plat_suspend(struct device *dev)
{
+ struct usb_hcd *hcd = dev_get_drvdata(dev);
+ struct xhci_plat_priv *priv = hcd_to_xhci_priv(hcd);
+
+ if (xhci_sideband_check(hcd)) {
+ priv->sideband_at_suspend = 1;
+ dev_dbg(dev, "sideband instance active, skip suspend.\n");
+ return 0;
+ }
+
return xhci_plat_suspend_common(dev);
}
@@ -535,6 +545,15 @@ static int xhci_plat_resume_common(struct device *dev, bool power_lost)
static int xhci_plat_resume(struct device *dev)
{
+ struct usb_hcd *hcd = dev_get_drvdata(dev);
+ struct xhci_plat_priv *priv = hcd_to_xhci_priv(hcd);
+
+ if (priv->sideband_at_suspend) {
+ priv->sideband_at_suspend = 0;
+ dev_dbg(dev, "sideband instance active, skip resume.\n");
+ return 0;
+ }
+
return xhci_plat_resume_common(dev, false);
}
diff --git a/drivers/usb/host/xhci-plat.h b/drivers/usb/host/xhci-plat.h
index fe4f95e690fa..cd07b22adc60 100644
--- a/drivers/usb/host/xhci-plat.h
+++ b/drivers/usb/host/xhci-plat.h
@@ -15,6 +15,7 @@ struct usb_hcd;
struct xhci_plat_priv {
const char *firmware_name;
unsigned long long quirks;
+ unsigned sideband_at_suspend:1;
bool power_lost;
void (*plat_start)(struct usb_hcd *);
int (*init_quirk)(struct usb_hcd *);
diff --git a/include/linux/usb.h b/include/linux/usb.h
index ec8d839e1e2b..f5bca317fa4c 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -635,6 +635,8 @@ struct usb3_lpm_parameters {
* @do_remote_wakeup: remote wakeup should be enabled
* @reset_resume: needs reset instead of resume
* @port_is_suspended: the upstream port is suspended (L2 or U3)
+ * @offload_at_suspend: offload activities during suspend is enabled.
+ * @offload_usage: number of offload activities happening on this usb device.
* @slot_id: Slot ID assigned by xHCI
* @l1_params: best effor service latency for USB2 L1 LPM state, and L1 timeout.
* @u1_params: exit latencies for USB3 U1 LPM state, and hub-initiated timeout.
@@ -647,7 +649,6 @@ struct usb3_lpm_parameters {
* parent->hub_delay + wHubDelay + tTPTransmissionDelay (40ns)
* Will be used as wValue for SetIsochDelay requests.
* @use_generic_driver: ask driver core to reprobe using the generic driver.
- * @offload_usage: number of offload activities happening on this usb device.
*
* Notes:
* Usbcore drivers should not set usbdev->state directly. Instead use
@@ -724,6 +725,8 @@ struct usb_device {
unsigned do_remote_wakeup:1;
unsigned reset_resume:1;
unsigned port_is_suspended:1;
+ unsigned offload_at_suspend:1;
+ int offload_usage;
enum usb_link_tunnel_mode tunnel_mode;
int slot_id;
@@ -734,8 +737,6 @@ struct usb_device {
u16 hub_delay;
unsigned use_generic_driver:1;
-
- int offload_usage;
};
#define to_usb_device(__dev) container_of_const(__dev, struct usb_device, dev)
--
2.49.0.604.gff1f9ca942-goog
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