linux-kernel - Re: [PATCH v3 0/5] Add function suspend/resume and remote wakeup support

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Date:   Mon, 6 Feb 2023 18:14:43 -0800
From:   Elson Serrao <quic_eserrao@...cinc.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "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 v3 0/5] Add function suspend/resume and remote wakeup
 support



On 2/6/2023 5:24 PM, Thinh Nguyen wrote:
> Hi Elson,
> 
> On Mon, Feb 06, 2023, Elson Roy Serrao wrote:
>> Changes in v3
>>   - Modified rw_capable flag to reflect the gadgets capability for wakeup
>>     signalling.
>>   - Added a check to configure wakeup bit in bmAttributes only if gadget
>>     is capable of triggering wakeup.
>>   - Implemented a gadget op for composite layer to inform UDC whether device
>>     is configured for remote wakeup.
>>   - Added a check in __usb_gadget_wakeup() API to trigger wakeup only if the
>>     device is configured for it.
>>   - Cosmetic changes in dwc3_gadget_func_wakeup() API.
>>
>> Changes in v2
>>   - Added a flag to indicate whether the device is remote wakeup capable.
>>   - Added an async parameter to _dwc3_gadget_wakeup() API and few cosmetic
>>     changes.
>>   - Added flags to reflect the state of  function suspend and function remote
>>     wakeup to usb_function struct rather than function specific struct (f_ecm).
>>   - Changed the dwc3_gadget_func__wakeup() API to run synchronously by first
>>     checking the link state and then sending the device notification. Also
>>     added debug log for DEVICE_NOTIFICATION generic cmd.
>>   - Added changes to arm the device for remotewakeup/function remotewakeup
>>     only if device is capable.
>>
>> An usb device can initate a remote wakeup and bring the link out of
>> suspend as dictated by the DEVICE_REMOTE_WAKEUP feature selector.
>> To achieve this an interface can invoke gadget_wakeup op and wait for the
>> device to come out of LPM. But the current polling based implementation
>> fails if the host takes a long time to drive the resume signaling specially
>> in high speed capable devices. Switching to an interrupt based approach is
>> more robust and efficient. This can be leveraged by enabling link status
>> change events and triggering a gadget resume when the link comes to active
>> state.
>>
>> If the device is enhanced super-speed capable, individual interfaces can
>> also be put into suspend state. An interface can be in function suspend
>> state even when the device is not in suspend state. Function suspend state
>> is retained throughout the device suspend entry and exit process.
>> A function can be put to function suspend through FUNCTION_SUSPEND feature
>> selector sent by the host. This setup packet also decides whether that
>> function is capable of initiating a function remote wakeup. When the
>> function sends a wakeup notification to the host the link must be first
>> brought to a non-U0 state and then this notification is sent.
>>
>> This change adds the infrastructure needed to support the above
>> functionalities.
>>
>> Elson Roy Serrao (5):
>>    usb: gadget: Properly configure the device for remote wakeup
>>    usb: dwc3: Add remote wakeup handling
>>    usb: gadget: Add function wakeup support
>>    usb: dwc3: Add function suspend and function wakeup support
>>    usb: gadget: f_ecm: Add suspend/resume and remote wakeup support
>>
>>   drivers/usb/dwc3/core.h               |   5 ++
>>   drivers/usb/dwc3/debug.h              |   2 +
>>   drivers/usb/dwc3/ep0.c                |  16 ++---
>>   drivers/usb/dwc3/gadget.c             | 110 +++++++++++++++++++++++++++++++---
>>   drivers/usb/gadget/composite.c        |  50 +++++++++++++++-
>>   drivers/usb/gadget/function/f_ecm.c   |  68 +++++++++++++++++++++
>>   drivers/usb/gadget/function/u_ether.c |  63 +++++++++++++++++++
>>   drivers/usb/gadget/function/u_ether.h |   4 ++
>>   drivers/usb/gadget/udc/core.c         |  46 ++++++++++++++
>>   drivers/usb/gadget/udc/trace.h        |   5 ++
>>   include/linux/usb/composite.h         |   6 ++
>>   include/linux/usb/gadget.h            |  12 ++++
>>   12 files changed, 371 insertions(+), 16 deletions(-)
>>
>> -- 
>> 2.7.4
>>
> 
> Hi Elson,
> 
> Thanks for your patches! I provided some comments. Hopefully they can be
> merged soon.
> 
> Thanks,
> Thinh

Hi Thinh

Thank you for your feedback/comments. I will address them in v4.

Regards
Elson