Re: To otg-fsm or not to otg-fsm? That is the question.

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On Mon, Aug 11, 2014 at 5:28 PM, Peter Chen <Peter.Chen@xxxxxxxxxxxxx> wrote:
> The OTG FSM at /usb/common/usb-otg-fsm.c is a software OTG FSM implementation
> which follows On-The-Go and Embedded Host Supplement to the USB Revision 2.0 Specification
> (Revision 2.0 version 1.1a) Chapter 7 State Diagrams.
>
> If the platform doesn't support hardware otg fsm, it should follow above fsm implementation since
> it follows the newest OTG & EH spec. Besides, as far as I know, the qualcomm uses
> chipidea core for its usb2, then it should be easy for qualcomm using this common
> otg fsm implementation.

OK.  sounds good.

Yes, the qualcomm chips use a chipidea core for usb2.  The main
difficulty, IMHO, will
be mapping the qcom charger state machine onto the generic OTG state
machine implementation
in usb-otg-fsm.  I'm not sure if I'll be able to embed the needed
functionality into the existing functions
called by the generic state machine, or if I'll need to add some new
entries to the function table
to handle this extra logic.

I'll probably try to get the driver working without the charger stuff
first, and then, once I have a
better idea of how the state machines map, try adding the charger
stuff.  If I feel like I need
to modify the generic state machine, I'll ask on list.  I'm a newbie
at USB stuff and I don't want
to break anything.

Thanks.

 -- Tim Bird
Senior Software Engineer, Sony Mobile
Architecture Group Chair, CE Workgroup, Linux Foundation
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