Re: [PATCH v12 6/6] usb: gadget: f_ecm: Add suspend/resume and remote wakeup support

[Elson Serrao]

On 3/16/2023 5:11 PM, Thinh Nguyen wrote:
> On Thu, Mar 16, 2023, Elson Roy Serrao wrote:
> > When host sends a suspend notification to the device, handle
> > the suspend callbacks in the function driver. Enhanced super
> > speed devices can support function suspend feature to put the
> > function in suspend state. Handle function suspend callback.
> >
> > Depending on the remote wakeup capability the device can either
> > trigger a remote wakeup or wait for the host initiated resume to
> > start data transfer again.
> >
> > Signed-off-by: Elson Roy Serrao <quic_eserrao@xxxxxxxxxxx>
> > ---
> >   drivers/usb/gadget/function/f_ecm.c   | 71 +++++++++++++++++++++++++++++++++++
> >   drivers/usb/gadget/function/u_ether.c | 63 +++++++++++++++++++++++++++++++
> >   drivers/usb/gadget/function/u_ether.h |  4 ++
> >   3 files changed, 138 insertions(+)
> >
> > diff --git a/drivers/usb/gadget/function/f_ecm.c b/drivers/usb/gadget/function/f_ecm.c
> > index a7ab30e..c43cd557 100644
> > --- a/drivers/usb/gadget/function/f_ecm.c
> > +++ b/drivers/usb/gadget/function/f_ecm.c
> > @@ -633,6 +633,8 @@ static void ecm_disable(struct usb_function *f)
> >   
> >   	usb_ep_disable(ecm->notify);
> >   	ecm->notify->desc = NULL;
> > +	f->func_suspended = false;
> > +	f->func_wakeup_armed = false;
> >   }
> >   
> >   /*-------------------------------------------------------------------------*/
> > @@ -885,6 +887,71 @@ static struct usb_function_instance *ecm_alloc_inst(void)
> >   	return &opts->func_inst;
> >   }
> >   
> > +static void ecm_suspend(struct usb_function *f)
> > +{
> > +	struct f_ecm *ecm = func_to_ecm(f);
> > +	struct usb_composite_dev *cdev = ecm->port.func.config->cdev;
> > +
> > +	if (f->func_suspended) {
> > +		DBG(cdev, "Function already suspended\n");
> > +		return;
> > +	}
> > +
> > +	DBG(cdev, "ECM Suspend\n");
> > +
> > +	gether_suspend(&ecm->port);
> > +}
> > +
> > +static void ecm_resume(struct usb_function *f)
> > +{
> > +	struct f_ecm *ecm = func_to_ecm(f);
> > +	struct usb_composite_dev *cdev = ecm->port.func.config->cdev;
> > +
> > +	/*
> > +	 * If the function is in USB3 Function Suspend state, resume is
> > +	 * canceled. In this case resume is done by a Function Resume request.
> > +	 */
> > +	if (f->func_suspended)
> > +		return;
> > +
> > +	DBG(cdev, "ECM Resume\n");
> > +
> > +	gether_resume(&ecm->port);
> > +}
> > +
> > +static int ecm_get_status(struct usb_function *f)
> > +{
> > +	struct usb_configuration *c = f->config;
> > +
> > +	/* D0 and D1 bit set to 0 if device is not wakeup capable */
> > +	if (!(USB_CONFIG_ATT_WAKEUP & c->bmAttributes))
> > +		return 0;
> > +
> > +	return (f->func_wakeup_armed ? USB_INTRF_STAT_FUNC_RW : 0) |
> > +		USB_INTRF_STAT_FUNC_RW_CAP;
> > +}
>
> Why do we need to implement ecm_get_status if it's already handled in
> composite.c now?

Yes this can be removed now. Will modify accordingly.
> > +
> > +static int ecm_func_suspend(struct usb_function *f, u8 options)
> > +{
> > +	struct usb_composite_dev *cdev = f->config->cdev;
> > +
> > +	DBG(cdev, "func susp %u cmd\n", options);
> > +
> > +	if (options & (USB_INTRF_FUNC_SUSPEND_LP >> 8)) {
>
> This feature selector doesn't indicate whether it's SetFeature or
> ClearFeature request. ecm_func_suspend is supposed to be for
> SetFeature(suspend) only. Perhaps we may have to define func_resume()
> for ClearFeature(suspend)?
>
> Thanks,
> Thinh
Host uses the same feature selector FUNCTION_SUSPEND for function 
suspend and function resume and func_suspend() callback can be used to
handle both the cases ? The distinction comes whether it is a 
SetFeature(FUNCTION_SUSPEND) or ClearFeature(FUNCTION_SUSPEND) which can 
be easily done in the func_suspend callback itself. We can add another 
callback func_resume specific to ClearFeature(FUNCTION_SUSPEND) but wont 
that be redundant and more callback handling on function 
driver/composite side as well? Please let me know your opinion.

Thanks
Elson

> > +		if (!f->func_suspended) {
> > +			ecm_suspend(f);
> > +			f->func_suspended = true;
> > +		}
> > +	} else {
> > +		if (f->func_suspended) {
> > +			f->func_suspended = false;
> > +			ecm_resume(f);
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +