Re: [PATCH v8 5/5] usb: gadget: f_ecm: Add suspend/resume and remote wakeup support

[Thinh Nguyen]

On Tue, Mar 14, 2023, Thinh Nguyen wrote:
> On Tue, Mar 14, 2023, Elson Serrao wrote:
> > 
> > 
> > On 3/13/2023 1:27 PM, Thinh Nguyen wrote:
> > > On Mon, Mar 13, 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   | 68 +++++++++++++++++++++++++++++++++++
> > > >   drivers/usb/gadget/function/u_ether.c | 63 ++++++++++++++++++++++++++++++++
> > > >   drivers/usb/gadget/function/u_ether.h |  4 +++
> > > >   3 files changed, 135 insertions(+)
> > > > 
> > > > diff --git a/drivers/usb/gadget/function/f_ecm.c b/drivers/usb/gadget/function/f_ecm.c
> > > > index a7ab30e..d50c1a4 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 +887,68 @@ 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)
> > > > +{
> > > > +	return (f->func_wakeup_armed ? USB_INTRF_STAT_FUNC_RW : 0) |
> > > > +		USB_INTRF_STAT_FUNC_RW_CAP;
> > > 
> > > Need to check the usb configuration is if it's wakeup_capable.
> > > 
> > > > +}
> > > > +
> > > > +static int ecm_func_suspend(struct usb_function *f, u8 options)
> > > > +{
> > > > +	struct f_ecm *ecm = func_to_ecm(f);
> > > > +	struct usb_composite_dev *cdev = ecm->port.func.config->cdev;
> > > > +
> > > > +	DBG(cdev, "func susp %u cmd\n", options);
> > > > +
> > > > +	f->func_wakeup_armed = !!(options & (USB_INTRF_FUNC_SUSPEND_RW >> 8));
> > > 
> > > Same here. Check config's bmAttributes if it's remote wakeup capable
> > > before arming for remote wakeup.
> > > 
> > Done. I will add that check for above two cases.
> > > > +
> > > > +	if (options & (USB_INTRF_FUNC_SUSPEND_LP >> 8)) {
> > > > +		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;
> > > 
> > > Need to return negative error if SetFeature fails. We should fix the
> > > composite layer to allow for protocal STALL here. Host needs to know if
> > > it should proceed to put the function in suspend.
> > > 
> > > Thanks,
> > > Thinh
> > > 
> > 
> > Could you please clarify what SetFeature fail here means? The host puts the
> > function in function suspend state through this SetFeature request.
> > If the device is not configured for remote wakeup (bmAtrributes wakeup bit),
> > like you mentioned above we should not arm the function for remote wakeup.
> > But the host is free to put the function in function suspend state and wake
> > it up through host initiated function resume right?
> > 
> 
> I mean if we want to tell the host that a feature cannot be set or that
> it doesn't exist, we should respond with a protocol STALL. How the host
> respond to the rejected SetFeature request is up to the host. But we
> should at least let the host know that.
> 
> I'm suggesting to remove the setting of value = 0 in composite.c:
> 
> -- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -2000,7 +2000,6 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
>                                 ERROR(cdev,
>                                       "func_suspend() returned error %d\n",
>                                       value);
> -                               value = 0;
>                         }
>                         break;
>                 }
> 
> 
> i.e. we should allow the return value to go through.
> 

Also, I imagine there are cases where we don't want the host to put the
device in suspend because it lacks remote wakeup. e.g. a HID device such
as a keyboard (though it's a bit odd to see one without remote wake
capability)

Thanks,
Thinh