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

[Elson Serrao <quic_eserrao@quicinc.com>]

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@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.
>>
> 
> 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?

Thanks
Elson