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

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

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@quicinc.com>
> > > ---
> > >   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.

Thanks,
Thinh