Re: [PATCH v4 7/9] usb: dwc3: Registering a role switch in the DRD code.

[John Stultz <john.stultz@linaro.org>]

On Tue, Oct 29, 2019 at 2:21 AM Felipe Balbi <balbi@kernel.org> wrote:
> John Stultz <john.stultz@linaro.org> writes:
> > From: Yu Chen <chenyu56@huawei.com>
> >
> > The Type-C drivers use USB role switch API to inform the
> > system about the negotiated data role, so registering a role
> > switch in the DRD code in order to support platforms with
> > USB Type-C connectors.
> >
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > CC: ShuFan Lee <shufan_lee@richtek.com>
> > Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> > Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
> > Cc: Yu Chen <chenyu56@huawei.com>
> > Cc: Felipe Balbi <balbi@kernel.org>
> > Cc: Hans de Goede <hdegoede@redhat.com>
> > Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> > Cc: Jun Li <lijun.kernel@gmail.com>
> > Cc: Valentin Schneider <valentin.schneider@arm.com>
> > Cc: Jack Pham <jackp@codeaurora.org>
> > Cc: linux-usb@vger.kernel.org
> > Cc: devicetree@vger.kernel.org
> > Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > Signed-off-by: Yu Chen <chenyu56@huawei.com>
> > Signed-off-by: John Stultz <john.stultz@linaro.org>
> > ---
> > v2: Fix role_sw and role_switch_default_mode descriptions as
> >     reported by kbuild test robot <lkp@intel.com>
> >
> > v3: Split out the role-switch-default-host logic into its own
> >     patch
> > ---
> >  drivers/usb/dwc3/Kconfig |  1 +
> >  drivers/usb/dwc3/core.h  |  3 ++
> >  drivers/usb/dwc3/drd.c   | 66 +++++++++++++++++++++++++++++++++++++++-
> >  3 files changed, 69 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
> > index 89abc6078703..1104745c41a9 100644
> > --- a/drivers/usb/dwc3/Kconfig
> > +++ b/drivers/usb/dwc3/Kconfig
> > @@ -44,6 +44,7 @@ config USB_DWC3_DUAL_ROLE
> >       bool "Dual Role mode"
> >       depends on ((USB=y || USB=USB_DWC3) && (USB_GADGET=y || USB_GADGET=USB_DWC3))
> >       depends on (EXTCON=y || EXTCON=USB_DWC3)
> > +     select USB_ROLE_SWITCH
>
> so even those using DWC3 as a peripheral-only or host-only driver will
> need role switch?

So, just to clarify, the select is added to the
CONFIG_USB_DWC3_DUAL_ROLE, wouldn't peripheral-only or host-only
drivers select USB_DWC3_GADGET or USB_DWC3_HOST instead?

Even so, if you'd prefer I can avoid the select, and add more #ifdef
CONFIG_USB_ROLE_SWITCH around the logic added in this patch. I just
worry it makes getting a valid config for some devices more complex
and clutters the logic a touch.

> > +static int dwc3_usb_role_switch_set(struct device *dev, enum usb_role role)
> > +{
> > +     struct dwc3 *dwc = dev_get_drvdata(dev);
> > +     u32 mode;
> > +
> > +     switch (role) {
> > +     case USB_ROLE_HOST:
> > +             mode = DWC3_GCTL_PRTCAP_HOST;
> > +             break;
> > +     case USB_ROLE_DEVICE:
> > +             mode = DWC3_GCTL_PRTCAP_DEVICE;
> > +             break;
> > +     default:
> > +             mode = DWC3_GCTL_PRTCAP_DEVICE;
> > +             break;
> > +     }
> > +
> > +     dwc3_set_mode(dwc, mode);
> > +     return 0;
> > +}
>
> role switching is starting to get way too complicated in DWC3. We now
> have a function that queues a work on the system_freezable_wq that will
> configure PHY and change PRTCAP. Is there a way we can simplify some of
> this a little?

I'm sorry, could you expand a bit on this point? I'm not sure I quite
see what you are envisioning as a simpler role_switch set handler? Is
the objection that I'm calling dwc3_set_mode() and instead should be
calling some non-static variant of __dwc3_set_mode() directly?