linux-kernel - Re: [PATCH v10 5/5] usb: gadget: f_ecm: Add suspend/resume and remote wakeup support

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Message-ID: <20230315194733.yjp5ddymehxm6abl@synopsys.com>
Date:   Wed, 15 Mar 2023 19:47:40 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Elson Roy Serrao <quic_eserrao@...cinc.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "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 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;

BR,
Thinh

> +
> +	f->func_wakeup_armed = !!(options & (USB_INTRF_FUNC_SUSPEND_RW >> 8));
> +
> +	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;
> +}
> +