linux-kernel - Re: [PATCH v7 2/5] usb: dwc3: Add remote wakeup handling

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Date:   Fri, 10 Mar 2023 23:21:28 +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 v7 2/5] usb: dwc3: Add remote wakeup handling

On Thu, Mar 09, 2023, Elson Roy Serrao wrote:
> An usb device can initate a remote wakeup and bring the link out of
> suspend as dictated by the DEVICE_REMOTE_WAKEUP feature selector.
> Add support to handle this packet and set the remote wakeup capability.
> 
> Some hosts may take longer time to initiate the resume signaling after
> device triggers a remote wakeup. So add async support to the wakeup API
> by enabling link status change events.
> 
> Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
> ---
>  drivers/usb/dwc3/core.h   |  2 ++
>  drivers/usb/dwc3/ep0.c    |  5 ++++
>  drivers/usb/dwc3/gadget.c | 76 +++++++++++++++++++++++++++++++++++++++++++----
>  3 files changed, 77 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index b1bd631..416e0ef 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -1113,6 +1113,7 @@ struct dwc3_scratchpad_array {
>   *	3	- Reserved
>   * @dis_metastability_quirk: set to disable metastability quirk.
>   * @dis_split_quirk: set to disable split boundary.
> + * @wakeup_configured: set if the device is configured for remote wakeup.
>   * @imod_interval: set the interrupt moderation interval in 250ns
>   *			increments or 0 to disable.
>   * @max_cfg_eps: current max number of IN eps used across all USB configs.
> @@ -1331,6 +1332,7 @@ struct dwc3 {
>  
>  	unsigned		dis_split_quirk:1;
>  	unsigned		async_callbacks:1;
> +	unsigned		wakeup_configured:1;
>  
>  	u16			imod_interval;
>  
> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
> index 61de693..442d8fe 100644
> --- a/drivers/usb/dwc3/ep0.c
> +++ b/drivers/usb/dwc3/ep0.c
> @@ -356,6 +356,9 @@ static int dwc3_ep0_handle_status(struct dwc3 *dwc,
>  				usb_status |= 1 << USB_DEV_STAT_U1_ENABLED;
>  			if (reg & DWC3_DCTL_INITU2ENA)
>  				usb_status |= 1 << USB_DEV_STAT_U2_ENABLED;
> +		} else {
> +			usb_status |= dwc->gadget->wakeup_armed <<
> +					USB_DEVICE_REMOTE_WAKEUP;
>  		}
>  
>  		break;
> @@ -476,6 +479,8 @@ static int dwc3_ep0_handle_device(struct dwc3 *dwc,
>  
>  	switch (wValue) {
>  	case USB_DEVICE_REMOTE_WAKEUP:
> +		if (dwc->wakeup_configured)
> +			dwc->gadget->wakeup_armed = set;

We should set ret = -EINVAL in the else case so the device will respond
with a protocol STALL rejecting the request rather than silently
accepting it.

Thanks,
Thinh