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 23:01:07 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Elson Serrao <quic_eserrao@...cinc.com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "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, Elson Serrao wrote:
> 
> On 3/15/2023 2:15 PM, Thinh Nguyen wrote:
> > 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
> 
> Yeah agree with that. We check for function_wakeup_armed flag before sending
> remote wakeup in composite.c. So it makes more sense
> to set/reset this flag in composite.c itself. I will make that change
> and upload v12 along with fixing 'value = 0' removal that we discussed
> earlier. Please let me know if that is fine
> 

Since we don't go through the func_suspend() anymore, let's keep it as
is for now. If you're in composite.c, then you can skip doing
func_suspend() if remote_wake is not supported when host requested.

Thanks,
Thinh