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

[Thinh Nguyen]

On Tue, Mar 14, 2023, Elson Serrao wrote:
> 
> 
> On 3/14/2023 1:45 PM, Thinh Nguyen wrote:
> > 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
> 
> Sound good. I will make that change. Would you prefer this change (i.e
> removing value = 0  in composite.c) to be part of this series OR should I
> upload a separate change for this?
> 

That change can be separated from this series. Let's try to get this
series in merged.

Thanks,
Thinh