linux-kernel - Re: [PATCH v10 5/5] usb: gadget: f_ecm: Add suspend/resume and remote wakeup support

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Date:   Wed, 15 Mar 2023 21:15:43 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Elson Roy Serrao <quic_eserrao@...cinc.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>
Subject: Re: [PATCH v10 5/5] usb: gadget: f_ecm: Add suspend/resume and remote
 wakeup support

On Wed, Mar 15, 2023, Thinh Nguyen wrote:
> On Wed, Mar 15, 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@...cinc.com>
> > ---
> >  drivers/usb/gadget/function/f_ecm.c   | 77 +++++++++++++++++++++++++++++++++++
> >  drivers/usb/gadget/function/u_ether.c | 63 ++++++++++++++++++++++++++++
> >  drivers/usb/gadget/function/u_ether.h |  4 ++
> >  3 files changed, 144 insertions(+)
> > 
> > diff --git a/drivers/usb/gadget/function/f_ecm.c b/drivers/usb/gadget/function/f_ecm.c
> > index a7ab30e..fea07ab 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 +887,77 @@ 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;
> > +}
> > +
> > +static int ecm_func_suspend(struct usb_function *f, u8 options)
> > +{
> > +	struct usb_configuration *c = f->config;
> > +
> > +	DBG(c->cdev, "func susp %u cmd\n", options);
> > +
> > +	/* Respond with negative errno if request is not supported */
> > +	if (!(USB_CONFIG_ATT_WAKEUP & c->bmAttributes))
> > +		return -EINVAL;
> 
> We only need to return early if the host tries to enable remote wake
> while the device isn't capable of it:
> 
> 	wakeup_sel = !!(options & (USB_INTRF_FUNC_SUSPEND_RW >> 8));
> 	if (wakeup_sel && !(USB_CONFIG_ATT_WAKEUP & c->bmAttributes))
> 		return -EINVAL;
> 
> 	f->func_wakeup_armed = wakeup_sel;
> 

Also, I notice that we can't differentiate between ClearFeature() and
SetFeature() in f->func_suspend(). Perhaps we should handle arming the
remote wakeup in the composite layer so we can set/clear the remote
wake. It's common across multiple devices. It's probably better to be
there.

Thanks,
Thinh