> -----Original Message-----
> From: Peter Chen [mailto:hzpeterc...@gmail.com]
> Sent: Wednesday, May 25, 2016 10:44 AM
> To: Roger Quadros <rog...@ti.com>
> Cc: peter.c...@freescale.com; ba...@kernel.org; t...@atomide.com;
> gre...@linuxfoundation.org; dan.j.willi...@intel.com;
> mathias.ny...@linux.intel.com; joao.pi...@synopsys.com;
> sergei.shtyl...@cogentembedded.com; jun...@freescale.com;
> grygorii.stras...@ti.com; yoshihiro.shimoda...@renesas.com;
> r...@kernel.org; nsek...@ti.com; b-...@ti.com; linux-usb@vger.kernel.org;
> linux-o...@vger.kernel.org; linux-ker...@vger.kernel.org;
> devicet...@vger.kernel.org
> Subject: Re: [PATCH v8 08/14] usb: otg: add OTG/dual-role core
>
> On Tue, May 24, 2016 at 12:45:46PM +0300, Roger Quadros wrote:
> > Hi Peter,
> >
> > I have one question here. Please see below.
> >
> > On 13/05/16 13:03, Roger Quadros wrote:
> > > It provides APIs for the following tasks
> > >
> > > - Registering an OTG/dual-role capable controller
> > > - Registering Host and Gadget controllers to OTG core
> > > - Providing inputs to and kicking the OTG state machine
> > >
> > > Provide a dual-role device (DRD) state machine.
> > > DRD mode is a reduced functionality OTG mode. In this mode we don't
> > > support SRP, HNP and dynamic role-swap.
> > >
> > > In DRD operation, the controller mode (Host or Peripheral) is
> > > decided based on the ID pin status. Once a cable plug (Type-A or
> > > Type-B) is attached the controller selects the state and doesn't
> > > change till the cable in unplugged and a different cable type is
> > > inserted.
> > >
> > > As we don't need most of the complex OTG states and OTG timers we
> > > implement a lean DRD state machine in usb-otg.c.
> > > The DRD state machine is only interested in 2 hardware inputs 'id'
> > > and 'b_sess_vld'.
> > >
> > > Signed-off-by: Roger Quadros <rog...@ti.com>
> > > ---
> > > drivers/usb/common/Makefile | 2 +-
> > > drivers/usb/common/usb-otg.c | 1042
> ++++++++++++++++++++++++++++++++++++++++++
> > > drivers/usb/core/Kconfig | 4 +-
> > > include/linux/usb/gadget.h | 2 +
> > > include/linux/usb/hcd.h | 1 +
> > > include/linux/usb/otg-fsm.h | 7 +
> > > include/linux/usb/otg.h | 154 ++++++-
> > > 7 files changed, 1206 insertions(+), 6 deletions(-) create mode
> > > 100644 drivers/usb/common/usb-otg.c
> > >
> >
> > <snip>
> >
> > > +
> > > +/**
> > > + * usb_otg_register() - Register the OTG/dual-role device to OTG
> > > +core
> > > + * @dev: OTG/dual-role controller device.
> > > + * @config: OTG configuration.
> > > + *
> > > + * Registers the OTG/dual-role controller device with the USB OTG
> core.
> > > + *
> > > + * Return: struct usb_otg * if success, ERR_PTR() if error.
> > > + */
> > > +struct usb_otg *usb_otg_register(struct device *dev,
> > > + struct usb_otg_config *config) {
> > > + struct usb_otg *otg;
> > > + struct otg_wait_data *wait;
> > > + int ret = 0;
> > > +
> > > + if (!dev || !config || !config->fsm_ops)
> > > + return ERR_PTR(-EINVAL);
> > > +
> > > + /* already in list? */
> > > + mutex_lock(&otg_list_mutex);
> > > + if (usb_otg_get_data(dev)) {
> > > + dev_err(dev, "otg: %s: device already in otg list\n",
> > > + __func__);
> > > + ret = -EINVAL;
> > > + goto unlock;
> > > + }
> > > +
> > > + /* allocate and add to list */
> > > + otg = kzalloc(sizeof(*otg), GFP_KERNEL);
> > > + if (!otg) {
> > > + ret = -ENOMEM;
> > > + goto unlock;
> > > + }
> > > +
> > > + otg->dev = dev;
> > > + otg->caps = config->otg_caps;
> >
> > Here, we should be checking if user needs to disable any OTG features.
> > So,
> >
> > if (dev->of_node)
> > of_usb_update_otg_caps(dev->of_node, &otg->caps);
> >
> > Do you agree?
> > This means we need to change otg->caps from 'struct usb_otg_caps *caps;'
> > to 'struct usb_otg_caps caps;' so that we can modify the local copy
> > instead of the one passed by the OTG controller.
>
> Why can't modify the one from OTG controller directly?
Yes, if user wants to disable any OTG features, this should have been
done in 'config->otg_caps', if not, 'config->otg_caps' from controller
driver is invalid and making no sense.
>
> >
> > We can also move of_usb_update_otg_caps() to otg.h.
> >
> > We will also need to modify the udc-core code so that it sets
> > gadget->otg_caps to the modified otg_caps from the OTG core. This will
> > ensure that the right OTG descriptors are sent.
> >
> > So we will have to introduce an API.
> >
> > struct usb_otg_caps *usb_otg_get_otg_caps(struct device *otg_dev)
> >
> > And in udc-core.c,
> >
> > static int udc_bind_to_driver(struct usb_udc *udc, struct
> > usb_gadget_driver *driver) { ..
> > ret = driver->bind(udc->gadget, driver);
> > if (ret)
> > goto err1;
> >
> > /* If OTG, the otg core starts the UDC when needed */
> > if (udc->gadget->otg_dev) {
> > + udc->gadget->is_otg = true;
>
> gadget->is_otg is only set to true if fully OTG is supported and it
> needs to send OTG descriptors at this case. DRD devices should not send
> OTG descriptors.
>
> > + udc->gadget->otg_caps = usb_otg_get_otg_caps(udc->gadget-
> >otg_dev);
>
> Getting otg capabilities should be prior to driver->bind since
> usb_otg_descriptor_init is called at that. Besides, Gadget driver may be
> probed before otg driver is registered
>
> I am wonder if we can implement defer probe for gadget/udc/host driver if
> otg driver is not probed, in that case, some designs can be simpler like
> wait list in otg driver.
I even don't see much benefit of this kind of random order of OTG/HCD/GADGET
registration, anyway OTG register can be done firstly.
HCD and GADGET are both separated drivers, but OTG is newly added
and what we need is just a registration in controller driver.
>
> > mutex_unlock(&udc_lock);
> > usb_otg_register_gadget(udc->gadget, &otg_gadget_intf);
> > mutex_lock(&udc_lock);
> > } else {
> > ret = usb_gadget_udc_start(udc);
> > if (ret) {
> > driver->unbind(udc->gadget);
> > goto err1;
> > }
> > usb_udc_connect_control(udc);
> > }
> > ..
> > }
> >
> > What do you say?
> >
> > regards,
> > -roger
> > --
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>
> --
>
> Best Regards,
> Peter Chen
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