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

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Date:   Thu, 9 Feb 2017 12:12:53 +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

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.


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
>

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