linux-kernel - Re: [PATCH v2] usb: dwc2: drd: fix soft connect when gadget is unconfigured

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Date:   Tue, 15 Feb 2022 18:19:19 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Fabrice Gasnier <fabrice.gasnier@...s.st.com>
Cc:     hminas@...opsys.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        amelie.delaunay@...s.st.com, alexandre.torgue@...s.st.com
Subject: Re: [PATCH v2] usb: dwc2: drd: fix soft connect when gadget is
 unconfigured

On Tue, Feb 15, 2022 at 04:42:46PM +0100, Fabrice Gasnier wrote:
> On 2/15/22 3:04 PM, Greg KH wrote:
> > On Tue, Feb 15, 2022 at 12:04:19PM +0100, Fabrice Gasnier wrote:
> >> When the gadget driver hasn't been (yet) configured, and the cable is
> >> connected to a HOST, the SFTDISCON gets cleared unconditionally, so the
> >> HOST tries to enumerate it.
> >> At the host side, this can result in a stuck USB port or worse. When
> >> getting lucky, some dmesg can be observed at the host side:
> >>  new high-speed USB device number ...
> >>  device descriptor read/64, error -110
> >>
> >> Fix it in drd, by checking the enabled flag before calling
> >> dwc2_hsotg_core_connect(). It will be called later, once configured,
> >> by the normal flow:
> >> - udc_bind_to_driver
> >>  - usb_gadget_connect
> >>    - dwc2_hsotg_pullup
> >>      - dwc2_hsotg_core_connect
> >>
> >> Fixes: 17f934024e84 ("usb: dwc2: override PHY input signals with usb role switch support")
> >> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
> >> ---
> >> Changes in v2:
> >> - Fix build error: 'struct dwc2_hsotg' has no member named 'enabled';
> >>   as reported by the kernel test robot.
> >>   https://lore.kernel.org/all/202202112236.AwoOTtHO-lkp@intel.com/
> >>   Add dwc2_is_device_enabled() macro to handle this.
> >> ---
> >>  drivers/usb/dwc2/core.h | 2 ++
> >>  drivers/usb/dwc2/drd.c  | 6 ++++--
> >>  2 files changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/usb/dwc2/core.h b/drivers/usb/dwc2/core.h
> >> index 8a63da3..8a7751b 100644
> >> --- a/drivers/usb/dwc2/core.h
> >> +++ b/drivers/usb/dwc2/core.h
> >> @@ -1418,6 +1418,7 @@ void dwc2_hsotg_core_connect(struct dwc2_hsotg *hsotg);
> >>  void dwc2_hsotg_disconnect(struct dwc2_hsotg *dwc2);
> >>  int dwc2_hsotg_set_test_mode(struct dwc2_hsotg *hsotg, int testmode);
> >>  #define dwc2_is_device_connected(hsotg) (hsotg->connected)
> >> +#define dwc2_is_device_enabled(hsotg) ((hsotg)->enabled)
> > 
> > Why the extra ()?  dwc2_is_device_connected does not have it, so this
> > one probably should not either, right?
> 
> Hi Greg,
> 
> I was wondering the same, checkpatch complains without it:
> 
> CHECK: Macro argument 'hsotg' may be better as '(hsotg)' to avoid
> precedence issues

checkpatch is wrong here, this is a structure pointer, not anything you
could ever use that could be evaluated any other way.

> I can remove the extra () in a v3 if you wish ?

Please do.

thanks,

greg k-h