2021-08-04 07:07:34

by Wesley Cheng

Subject: [PATCH v2] usb: dwc3: gadget: Avoid runtime resume if disabling pullup

If the device is already in the runtime suspended state, any call to
the pullup routine will issue a runtime resume on the DWC3 core
device. If the USB gadget is disabling the pullup, then avoid having
to issue a runtime resume, as DWC3 gadget has already been
halted/stopped.

This fixes an issue where the following condition occurs:

usb_gadget_remove_driver()
-->usb_gadget_disconnect()
-->dwc3_gadget_pullup(0)
-->pm_runtime_get_sync() -> ret = 0
-->pm_runtime_put() [async]
-->usb_gadget_udc_stop()
-->dwc3_gadget_stop()
-->dwc->gadget_driver = NULL
...

dwc3_suspend_common()
-->dwc3_gadget_suspend()
-->DWC3 halt/stop routine skipped, driver_data == NULL

This leads to a situation where the DWC3 gadget is not properly
stopped, as the runtime resume would have re-enabled EP0 and event
interrupts, and since we avoided the DWC3 gadget suspend, these
resources were never disabled.

Fixes: 77adb8bdf422 ("usb: dwc3: gadget: Allow runtime suspend if UDC unbinded")
Signed-off-by: Wesley Cheng <[email protected]>
---
Changes in v2:
- Added fixes tag with the problem commit.

drivers/usb/dwc3/gadget.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index a29a4ca..5d08454 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2435,6 +2435,17 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
}

/*
+ * Avoid issuing a runtime resume if the device is already in the
+ * suspended state during gadget disconnect. DWC3 gadget was already
+ * halted/stopped during runtime suspend.
+ */
+ if (!is_on) {
+ pm_runtime_barrier(dwc->dev);
+ if (pm_runtime_suspended(dwc->dev))
+ return 0;
+ }
+
+ /*
* Check the return value for successful resume, or error. For a
* successful resume, the DWC3 runtime PM resume routine will handle
* the run stop sequence, so avoid duplicate operations here.
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

2021-08-04 12:26:45

by Felipe Balbi

Subject: Re: [PATCH v2] usb: dwc3: gadget: Avoid runtime resume if disabling pullup

Wesley Cheng <[email protected]> writes:

> If the device is already in the runtime suspended state, any call to
> the pullup routine will issue a runtime resume on the DWC3 core
> device. If the USB gadget is disabling the pullup, then avoid having
> to issue a runtime resume, as DWC3 gadget has already been
> halted/stopped.
>
> This fixes an issue where the following condition occurs:
>
> usb_gadget_remove_driver()
> -->usb_gadget_disconnect()
> -->dwc3_gadget_pullup(0)
> -->pm_runtime_get_sync() -> ret = 0
> -->pm_runtime_put() [async]
> -->usb_gadget_udc_stop()
> -->dwc3_gadget_stop()
> -->dwc->gadget_driver = NULL
> ...
>
> dwc3_suspend_common()
> -->dwc3_gadget_suspend()
> -->DWC3 halt/stop routine skipped, driver_data == NULL
>
> This leads to a situation where the DWC3 gadget is not properly
> stopped, as the runtime resume would have re-enabled EP0 and event
> interrupts, and since we avoided the DWC3 gadget suspend, these
> resources were never disabled.
>
> Fixes: 77adb8bdf422 ("usb: dwc3: gadget: Allow runtime suspend if UDC unbinded")
> Signed-off-by: Wesley Cheng <[email protected]>

Acked-by: Felipe Balbi <[email protected]>

--
balbi