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.

Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
---
 drivers/usb/core/driver.c         | 10 ++++++++++
 drivers/usb/core/hcd.c            |  1 +
 drivers/usb/core/usb.c            |  1 +
 drivers/usb/dwc3/core.c           | 13 +++++++++++++
 drivers/usb/dwc3/core.h           |  8 ++++++++
 drivers/usb/host/xhci-plat.c      | 10 ++++++++++
 drivers/usb/host/xhci-plat.h      |  7 +++++++
 sound/usb/qcom/qc_audio_offload.c |  3 +++
 8 files changed, 53 insertions(+)

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index c1ba5ed15214..83726bf88fb6 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1583,6 +1583,11 @@ int usb_suspend(struct device *dev, pm_message_t msg)
 	struct usb_device	*udev = to_usb_device(dev);
 	int r;
 
+	if (msg.event == PM_EVENT_SUSPEND && usb_sideband_check(udev)) {
+		dev_info(dev, "device active, skip %s", __func__);
+		return 0;
+	}
+
 	unbind_no_pm_drivers_interfaces(udev);
 
 	/* From now on we are sure all drivers support suspend/resume
@@ -1619,6 +1624,11 @@ int usb_resume(struct device *dev, pm_message_t msg)
 	struct usb_device	*udev = to_usb_device(dev);
 	int			status;
 
+	if (msg.event == PM_EVENT_RESUME && usb_sideband_check(udev)) {
+		dev_info(dev, "device active, skip %s", __func__);
+		return 0;
+	}
+
 	/* For all calls, take the device back to full power and
 	 * tell the PM core in case it was autosuspended previously.
 	 * Unbind the interfaces that will need rebinding later,
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 1ff7d901fede..a41f1fa425bd 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -2593,6 +2593,7 @@ struct usb_hcd *__usb_create_hcd(const struct hc_driver *driver,
 	timer_setup(&hcd->rh_timer, rh_timer_func, 0);
 #ifdef CONFIG_PM
 	INIT_WORK(&hcd->wakeup_work, hcd_resume_work);
+	atomic_set(&hcd->sb_usage_count, 0);
 #endif
 
 	INIT_WORK(&hcd->died_work, hcd_died_work);
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 0b4685aad2d5..69fbbc6f865f 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -671,6 +671,7 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
 	dev->state = USB_STATE_ATTACHED;
 	dev->lpm_disable_count = 1;
 	atomic_set(&dev->urbnum, 0);
+	atomic_set(&dev->sb_usage_count, 0);
 
 	INIT_LIST_HEAD(&dev->ep0.urb_list);
 	dev->ep0.desc.bLength = USB_DT_ENDPOINT_SIZE;
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 2fdafbcbe44c..d1ad817ff564 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -2550,8 +2550,15 @@ static int dwc3_runtime_idle(struct device *dev)
 static int dwc3_suspend(struct device *dev)
 {
 	struct dwc3	*dwc = dev_get_drvdata(dev);
+	struct platform_device *xhci = dwc->xhci;
 	int		ret;
 
+	if (xhci && xhci_sideband_check(xhci->dev.driver_data)) {
+		dev_info(dev, "device active, skip %s", __func__);
+		return 0;
+	}
+
+
 	ret = dwc3_suspend_common(dwc, PMSG_SUSPEND);
 	if (ret)
 		return ret;
@@ -2564,8 +2571,14 @@ static int dwc3_suspend(struct device *dev)
 static int dwc3_resume(struct device *dev)
 {
 	struct dwc3	*dwc = dev_get_drvdata(dev);
+	struct platform_device *xhci = dwc->xhci;
 	int		ret;
 
+	if (xhci && xhci_sideband_check(xhci->dev.driver_data)) {
+		dev_info(dev, "device active, skip %s", __func__);
+		return 0;
+	}
+
 	pinctrl_pm_select_default_state(dev);
 
 	pm_runtime_disable(dev);
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 80047d0df179..e06d597ee3b0 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -26,6 +26,7 @@
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
 #include <linux/usb/otg.h>
+#include <linux/usb/hcd.h>
 #include <linux/usb/role.h>
 #include <linux/ulpi/interface.h>
 
@@ -1704,4 +1705,11 @@ static inline void dwc3_ulpi_exit(struct dwc3 *dwc)
 { }
 #endif
 
+#if IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND)
+extern bool xhci_sideband_check(struct usb_hcd *hcd);
+#else
+static inline bool xhci_sideband_check(struct usb_hcd *hcd)
+{ return false; }
+#endif
+
 #endif /* __DRIVERS_USB_DWC3_CORE_H */
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index 6e49ef1908eb..b730320df70d 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -456,6 +456,11 @@ static int xhci_plat_suspend_common(struct device *dev, struct pm_message pmsg)
 	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
 	int ret;
 
+	if (pmsg.event == PM_EVENT_SUSPEND && xhci_sideband_check(hcd)) {
+		dev_info(dev, "device active, skip %s", __func__);
+		return 0;
+	}
+
 	if (pm_runtime_suspended(dev))
 		pm_runtime_resume(dev);
 
@@ -499,6 +504,11 @@ static int xhci_plat_resume_common(struct device *dev, struct pm_message pmsg)
 	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
 	int ret;
 
+	if (pmsg.event == PM_EVENT_RESUME && xhci_sideband_check(hcd)) {
+		dev_info(dev, "device active, skip %s", __func__);
+		return 0;
+	}
+
 	if (!device_may_wakeup(dev) && (xhci->quirks & XHCI_SUSPEND_RESUME_CLKS)) {
 		ret = clk_prepare_enable(xhci->clk);
 		if (ret)
diff --git a/drivers/usb/host/xhci-plat.h b/drivers/usb/host/xhci-plat.h
index 6475130eac4b..432a040c81e5 100644
--- a/drivers/usb/host/xhci-plat.h
+++ b/drivers/usb/host/xhci-plat.h
@@ -30,4 +30,11 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev,
 void xhci_plat_remove(struct platform_device *dev);
 extern const struct dev_pm_ops xhci_plat_pm_ops;
 
+#if IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND)
+extern bool xhci_sideband_check(struct usb_hcd *hcd);
+#else
+static inline bool xhci_sideband_check(struct usb_hcd *hcd)
+{ return false; }
+#endif
+
 #endif	/* _XHCI_PLAT_H */
diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
index 2dc651cd3d05..c82b5dbef2d7 100644
--- a/sound/usb/qcom/qc_audio_offload.c
+++ b/sound/usb/qcom/qc_audio_offload.c
@@ -1516,8 +1516,11 @@ static void handle_uaudio_stream_req(struct qmi_handle *handle,
 			mutex_lock(&chip->mutex);
 			subs->opened = 0;
 			mutex_unlock(&chip->mutex);
+		} else {
+			xhci_sideband_get(uadev[pcm_card_num].sb);
 		}
 	} else {
+		xhci_sideband_put(uadev[pcm_card_num].sb);
 		info = &uadev[pcm_card_num].info[info_idx];
 		if (info->data_ep_pipe) {
 			ep = usb_pipe_endpoint(uadev[pcm_card_num].udev,
-- 
2.47.0.rc0.187.ge670bccf7e-goog

On Wed, Oct 09, 2024 at 05:42:59AM +0000, Guan-Yu Lin wrote:
> 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.
> 
> Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
> ---
>  drivers/usb/core/driver.c         | 10 ++++++++++
>  drivers/usb/core/hcd.c            |  1 +
>  drivers/usb/core/usb.c            |  1 +
>  drivers/usb/dwc3/core.c           | 13 +++++++++++++
>  drivers/usb/dwc3/core.h           |  8 ++++++++
>  drivers/usb/host/xhci-plat.c      | 10 ++++++++++
>  drivers/usb/host/xhci-plat.h      |  7 +++++++
>  sound/usb/qcom/qc_audio_offload.c |  3 +++
>  8 files changed, 53 insertions(+)
> 
> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> index c1ba5ed15214..83726bf88fb6 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -1583,6 +1583,11 @@ int usb_suspend(struct device *dev, pm_message_t msg)
>  	struct usb_device	*udev = to_usb_device(dev);
>  	int r;
>  
> +	if (msg.event == PM_EVENT_SUSPEND && usb_sideband_check(udev)) {
> +		dev_info(dev, "device active, skip %s", __func__);

When drivers work properly, they are quiet.  Why all of the loud
shouting in this patch as it goes about it's business?

also, __func__ is redundant in dev_*() calls :)

thanks,

greg k-h

On Wed, Oct 9, 2024 at 8:47 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Oct 09, 2024 at 05:42:59AM +0000, Guan-Yu Lin wrote:
> > @@ -1583,6 +1583,11 @@ int usb_suspend(struct device *dev, pm_message_t msg)
> >       struct usb_device       *udev = to_usb_device(dev);
> >       int r;
> >
> > +     if (msg.event == PM_EVENT_SUSPEND && usb_sideband_check(udev)) {
> > +             dev_info(dev, "device active, skip %s", __func__);
>
> When drivers work properly, they are quiet.  Why all of the loud
> shouting in this patch as it goes about it's business?
>
> also, __func__ is redundant in dev_*() calls :)
>
> thanks,
>
> greg k-h

Thanks for the suggestions. Let me switch to dev_dbg and remove
__func__ in the next patch.

Regards,
Guan-Yu