Re: [PATCH] usb: dwc3: Support the dwc3 host suspend/resume

[Manu Gautam]

Hi,


On 7/21/2017 12:28 PM, Baolin Wang wrote:
> For some mobile devices with strict power management, we also want to
> suspend the host when the slave was detached for power saving. Thus
> adding the host suspend/resume functions to support this requirement.


USB/PM core already takes care of suspending root-HUB/XHCI when
no device connected.

>
> We will issue the pm_suspend_ignore_children() for the dwc3 device,
> since we will resume the child device (xHCI device) in runtime resume
> callback (dwc3_host_resume()) of dwc3 device, now the dwc3 device's
> runtime state is not RPM_ACTIVE, which will block to resume its
> child device (xHCI device). Add ignore children flag can avoid this
> situation.

This defeats the basic purpose of runtime PM. Without ignore_children
once USB bus is suspended, dwc3 gets suspended and then dwc3 glue device.
Only requirement I see from the patch is to resume XHCI/root-hub on
dwc3 resume. I am sure there must be other way to deal with that e.g.
doing same from glue driver by using a wq or use pm_request_resume()

>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
> ---
>  drivers/usb/dwc3/core.c |   26 +++++++++++++++++++++++++-
>  drivers/usb/dwc3/core.h |    7 +++++++
>  drivers/usb/dwc3/host.c |   15 +++++++++++++++
>  3 files changed, 47 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 326b302..2be7ddc 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1193,6 +1193,7 @@ static int dwc3_probe(struct platform_device *pdev)
>  	pm_runtime_use_autosuspend(dev);
>  	pm_runtime_set_autosuspend_delay(dev, DWC3_DEFAULT_AUTOSUSPEND_DELAY);
>  	pm_runtime_enable(dev);
> +	pm_suspend_ignore_children(dev, true);
>  	ret = pm_runtime_get_sync(dev);
>  	if (ret < 0)
>  		goto err1;
> @@ -1292,15 +1293,27 @@ static int dwc3_remove(struct platform_device *pdev)
>  static int dwc3_suspend_common(struct dwc3 *dwc)

What is the trigger for runtime suspend now that you have ignore_children set.
>  {
>  	unsigned long	flags;
> +	int		ret;
>  
>  	switch (dwc->dr_mode) {
>  	case USB_DR_MODE_PERIPHERAL:
> +		spin_lock_irqsave(&dwc->lock, flags);
> +		dwc3_gadget_suspend(dwc);
> +		spin_unlock_irqrestore(&dwc->lock, flags);
> +		break;
>  	case USB_DR_MODE_OTG:
> +		ret = dwc3_host_suspend(dwc);
With DRD/OTG, if current mode is device and dwc3->xhci won't be valid.
You can refer to the patch that I pushed to address this.

> +		if (ret)
> +			return ret;
> +
>  		spin_lock_irqsave(&dwc->lock, flags);
>  		dwc3_gadget_suspend(dwc);
>  		spin_unlock_irqrestore(&dwc->lock, flags);
>  		break;
>  	case USB_DR_MODE_HOST:
> +		ret = dwc3_host_suspend(dwc);
> +		if (ret)
> +			return ret;
>  	default:
>  		/* do nothing */
>  		break;
> @@ -1322,12 +1335,23 @@ static int dwc3_resume_common(struct dwc3 *dwc)
>  
>  	switch (dwc->dr_mode) {
>  	case USB_DR_MODE_PERIPHERAL:
> +		spin_lock_irqsave(&dwc->lock, flags);
> +		dwc3_gadget_resume(dwc);
> +		spin_unlock_irqrestore(&dwc->lock, flags);
> +		break;
>  	case USB_DR_MODE_OTG:
> +		ret = dwc3_host_resume(dwc);
> +		if (ret)
> +			return ret;
> +
>  		spin_lock_irqsave(&dwc->lock, flags);
>  		dwc3_gadget_resume(dwc);
>  		spin_unlock_irqrestore(&dwc->lock, flags);
> -		/* FALLTHROUGH */
> +		break;
>  	case USB_DR_MODE_HOST:
> +		ret = dwc3_host_resume(dwc);
> +		if (ret)
> +			return ret;
>  	default:
>  		/* do nothing */
>  		break;
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index ea910ac..9b5a4eb 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1193,11 +1193,18 @@ static inline bool dwc3_is_usb31(struct dwc3 *dwc)
>  #if IS_ENABLED(CONFIG_USB_DWC3_HOST) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
>  int dwc3_host_init(struct dwc3 *dwc);
>  void dwc3_host_exit(struct dwc3 *dwc);
> +int dwc3_host_suspend(struct dwc3 *dwc);
> +int dwc3_host_resume(struct dwc3 *dwc);
>  #else
>  static inline int dwc3_host_init(struct dwc3 *dwc)
>  { return 0; }
>  static inline void dwc3_host_exit(struct dwc3 *dwc)
>  { }
> +
> +static inline int dwc3_host_suspend(struct dwc3 *dwc)
> +{ return 0; }
> +static inline int dwc3_host_resume(struct dwc3 *dwc)
> +{ return 0; }
>  #endif
>  
>  #if IS_ENABLED(CONFIG_USB_DWC3_GADGET) || IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
> diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
> index 76f0b0d..3fa4414 100644
> --- a/drivers/usb/dwc3/host.c
> +++ b/drivers/usb/dwc3/host.c
> @@ -16,6 +16,7 @@
>   */
>  
>  #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>  
>  #include "core.h"
>  
> @@ -151,3 +152,17 @@ void dwc3_host_exit(struct dwc3 *dwc)
>  			  dev_name(dwc->dev));
>  	platform_device_unregister(dwc->xhci);
>  }
> +
> +int dwc3_host_suspend(struct dwc3 *dwc)
> +{
> +	struct device *xhci = &dwc->xhci->dev;
> +
> +	return pm_runtime_suspend(xhci);
If ignore_children is not marked then xhci would indeed be suspended.

> +}
> +
> +int dwc3_host_resume(struct dwc3 *dwc)
> +{
> +	struct device *xhci = &dwc->xhci->dev;
> +
> +	return pm_runtime_resume(xhci);

Other than what I pushed in my patch -
("usb: dwc3: Don't reinitialize core during host bus-suspend/resume")
Just performing pm_request_resume or handling same in dwc3 glue
driver should be sufficient.
Also, what is trigger for runtime_resume for your platform?