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

From: Baolin Wang
Date: Fri Jul 21 2017 - 05:01:08 EST

On 21 July 2017 at 16:45, Manu Gautam <mgautam@xxxxxxxxxxxxxx> wrote:
> 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.

Correct, but what I mean is we can power off the dwc3 controller when
there are 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()

Ah, I will try 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.

If current mode is device, then xHCI device is always in suspend state.

> 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.

Yes.

> Also, what is trigger for runtime_resume for your platform?

In our platform glue layer, we have extcon events to notify there are
devices connected, then gule layer will resume dwc3 device.

--
Baolin.wang
Best Regards