linux-kernel - Re: [PATCH 0/8] usb: dwc3: add dual-role support

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Date:   Thu, 9 Feb 2017 17:08:20 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Roger Quadros <rogerq@...com>
Cc:     Felipe Balbi <balbi@...nel.org>, Tony Lindgren <tony@...mide.com>,
        peter.chen@...escale.com,
        Linux USB Mailing List <linux-usb@...r.kernel.org>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/8] usb: dwc3: add dual-role support

On Thu, Feb 9, 2017 at 1:19 PM, Roger Quadros <rogerq@...com> wrote:
> Vivek,
>
> On 09/02/17 08:42, Vivek Gautam wrote:
>> Hi Roger,
>>
>> On Mon, Jan 23, 2017 at 4:49 PM, Roger Quadros <rogerq@...com> wrote:
>>> Hi,
>>>
>>> We rely on the OTG controller block to provide us with
>>> VBUS and ID line status via an interrupt.
>>>
>>> This is then used to switch the controller between host, peripheral
>>> and idle roles based on the following table.
>>>
>>>     ID  VBUS    dual-role state
>>>     --  ----    ---------------
>>>     0   x       A_HOST - Host controller active
>>>     1   0       B_IDLE - Both Host and Gadget controllers inactive
>>>     1   1       B_PERIPHERAL - Gadget controller active
>>>
>>
>> Thanks for this series.
>> Sorry, i was held up with something else so couldn't take a look at it.
>> I will integrate this with my work, and add some basic extcon
>> support to enable passing vbus and id events to dwc3 layer to test
>> this out on msm platforms.
>
> I already have this done for one of our platforms to workaround
> a limitation with the OTG IP block on it.
> I can post it today and you can give your comments.

Okay, cool. Thanks. I will wait.


Regards
Vivek

>
> cheers,
> -roger
>>
>>
>> Regards
>> Vivek
>>
>>> Couple of things to clarify:
>>> - There is a small window where we can potentially miss an
>>> event related to OTG. I've added a comment in the code where this
>>> could happen. How can we prevent this? Is it better to just leave
>>> the OTG events unmasked (but keep otg_irq on ARM GIC disabled)
>>> so that any new events can be captured by the OTG event register
>>> and interrupt re-triggered if it has not been serviced by the
>>> previous interrupt.
>>> - I'm running the entire dual-role state change logic inside
>>> the threaded interrupt handler with dwc->lock (spinlock) held
>>> but IRQs enabled. OTG events are very rare i.e. manual intervention
>>> so I don't see this as a problem. Just wanted to double check.
>>> - Some SoC's (e.g. Qualcomm MSM) do not have the OTG controller block
>>> but do have both host and peripheral controllers and so can operate
>>> in dual role mode. Current series does not address this case.
>>> We can get dual-role to work with such SoCs if core.c can get
>>> information about ID and VBUS somehow (private interface
>>> from parent or directly read extcon?).
>>>
>>> cheers,
>>> -roger
>>>
>>> Roger Quadros (8):
>>>   usb: otg-fsm: Prevent build warning "VDBG" redefined
>>>   usb: dwc3-omap: Fix missing break in dwc3_omap_set_mailbox()
>>>   usb: dwc3: use BIT() macro where possible
>>>   usb: dwc3: core.h: add some register definitions
>>>   usb: dwc3: add dual-role support
>>>   ARM: dts: dra7x-evm: Enable dual-role mode for USB1
>>>   ARM: dts: am43xx: Enable dual-role mode for USB1
>>>   ARM: dts: am57xx-idk: Enable dual-role mode for USB2
>>>
>>>  arch/arm/boot/dts/am437x-gp-evm.dts      |   2 +-
>>>  arch/arm/boot/dts/am437x-sk-evm.dts      |   2 +-
>>>  arch/arm/boot/dts/am43x-epos-evm.dts     |   2 +-
>>>  arch/arm/boot/dts/am57xx-idk-common.dtsi |   2 +-
>>>  arch/arm/boot/dts/dra7-evm.dts           |   2 +-
>>>  arch/arm/boot/dts/dra72-evm-common.dtsi  |   2 +-
>>>  drivers/usb/common/usb-otg-fsm.c         |   7 +
>>>  drivers/usb/dwc3/core.c                  | 583 ++++++++++++++++++++++++++++++-
>>>  drivers/usb/dwc3/core.h                  | 312 ++++++++++++-----
>>>  drivers/usb/dwc3/dwc3-omap.c             |  49 +--
>>>  drivers/usb/dwc3/gadget.c                |  18 +-
>>>  drivers/usb/dwc3/gadget.h                |  20 +-
>>>  drivers/usb/phy/phy-fsl-usb.c            |   7 +
>>>  include/linux/usb/otg-fsm.h              |  15 -
>>>  14 files changed, 848 insertions(+), 175 deletions(-)
>>>
>>> --
>>> 2.7.4
>>>
>>
>
> --
> cheers,
> -roger



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