On 2/18/2020 8:18 PM, Bryan O'Donoghue wrote:
On 18/02/2020 13:23, Dwivedi, Avaneesh Kumar (avani) wrote:
On 2/18/2020 1:14 AM, Bryan O'Donoghue wrote:
On 16/02/2020 16:07, Dwivedi, Avaneesh Kumar (avani) wrote:
On 2/4/2020 8:40 AM, Bryan O'Donoghue wrote:
On 03/02/2020 19:35, Bjorn Andersson wrote:
On Thu 30 Jan 20:43 PST 2020, Avaneesh Kumar Dwivedi wrote:
Hi Avaneesh.
Hello Bryan, Thank you very much for your review comments.
Will be replying to your comments and will be posting new patchset
soon as per review comments.
Please aim for keeping the sort order in this file (ignore QCOM_APR
which obviously is in the wrong place)
+ tristate "QTI Embedded USB Debugger (EUD)"
+ depends on ARCH_QCOM
If we persist with the model of EXTCON you should "select EXTCON"
here.
I have asked this query with Bjorn Also against his review
comments, whether we need to persist with extcon or need to switch
to usb role switch framework, as we are notifying not only to usb
controller but also to pmic charger so in case we adopt usb role
switch then how we will notify to pmic charger to enable charging
battery ? Also as i mentioned there my dilema is it does not look
very apt to model EUD hw IP as c type connector, so please let me
know your views.
I think there's a desire to model USB ports as connector child nodes
of a USB controllers as opposed to the more generic extcon so, I
think the effort should probably be made to model it up as typec.
this comment is irrespective of your below comment (If we were to
support Control Peripheral where the local DWC3 controller has the
signals routed away entirely, then I think we would need to look into
modelling that in device tree - and using an overlay to show the DWC3
controller going away in Control Peripheral mode and coming back. )?
Yes, I think irrespective we should model this as a connector not an
extcon and I think you could do think you could do that as a typec
1. Using role-switch
2. Use the regulator API to capture EUD related charger messages
and trigger changes in the PMIC as opposed to using extcon
to notify.
I could be wrong about #2
HI Bryan,
Sorry for long pause on this thread, I went through USB role switch
framework and yes we can move to it for notification of VBUS event, but
i am not able to find a good example in upstream, of how battery charger
module can be notified about charger stop and charger start event if we
don't use extcon interface for notification. I am not sure it would be
simple regulator enable and disable call, i will discuss with PMIC guys
on this and will come back.
Can that work for you ?
Did not comprehend this comment fully. if possible can you give some
example.
My understanding is we are generally being encouraged to model ports
as connectors instead of extcon. I think it is possible to model your
port driver as a typec connector using USB role-switching and the
regulator API i.e. I don't think you really need extcon here.
Ah so, the EUD is a mux, that sits between the connector and the
controller, routing UTMI signals to an internal USB hub, which
in-turn has debug functions attached to the hub...
Yes that is correct understanding.
Can the Arm core see the hub ? I assume not ?
Not sure what is it mean by "Can the Arm core see the hub"?
In Debug mode will a DWC3 controller in host mode enumerate the
internal hub ? If so, is that a supported use-case ?
In debug mode DWC3 controller will only enumerate in device mode.
There are a few different modes - you should probably be clear on
which mode it is you are supporting.
Normal mode: (Bypass)
Port | EUD | Controller
Normal + debug hub mode: (Debug)
Port | EUD | Controller + HUB -> debug functions
Debug hub mode: (Control Peripheral)
Port | EUD | HUB -> debug functions
its not clear to me from the documentation or the code which mode it
is we are targeting to be supported here.
Its debug mode which we are supporting in driver.
I think you should support Debug mode only here, so that the Arm
core never has to deal with the situation where the USB connector
"goes away".
Can you please help what you mean by "so that the Arm core never has
to deal with the situation where the USB connector "goes away""
So my thinking is
- DWC3 in host mode
For argument sake, lets say an external self-powered hub is connected
and a number of USB devices are enumerated
- EUD switches to Control Peripheral mode
In this case what would happen ?
I am not getting clarity about this from spec document, what i
understand is in this case PHY signal to USB controller will get
stop(UTMI switch will block signal from USB PHY to USB controller), so
before to switching to control peripheral mode EUD should send detach
event to USB controller so that it can enter low power mode, let me know
if it is grossly wrong understanding. In any case we are not supporting
control peripheral mode in present state of driver.
If we were to support Control Peripheral where the local DWC3
controller has the signals routed away entirely, then I think we
would need to look into modelling that in device tree - and using an
overlay to show the DWC3 controller going away in Control Peripheral
mode and coming back.
debug mode is set run time via user, i will check how we can model
such scenario where device tree corresponding to a h/w module is only
valid in some scenario at run time. if possible please elaborate bit
more on your suggestion
If Debug mode is all you are trying to do support then I don't think
you really need to model that in DT.
However if intend to support Control Peripheral mode which as I
understand it, switches the UTMI signals away from a DWC3 controller
in Host mode, then I think you would need to use a DT overlay to
switch off the controller, before switching.
That's why I'm asking you about Control Peripheral mode - do you want
to support it - and if so, then what happens to DWC3 in host mode when
the UTMI signals go away ?
I think you've said you only want to support Debug mode, which makes
more sense to me.
Is Debug mode only valid when the DWC3 controller is in
peripheral/device mode and if so, should we be checking/enforcing that
somewhere - DT or EUD-driver code ?
Yes in debug mode DWC3 controller should always be in device mode, and i
believe this we can insure when we inform USB controller about attach
event after starting in debug mode, using role-switch framework isnt it?
may be i am not getting your statement, how device mode enumeration can
be enforced using DT ?
Also final thought since the EUD can operate in different modes, it
really should be a string that gets passed in - with the string name
aligning to the documentation "bypass", "debug" and so on, so that
the mode we are switching to is obvious to anybody who has the spec
and the driver.
you mean we should document that this driver works in debug mode
only? not clear on where one should pass "debug" and "bypass" string?
You have a routine to switch to debug mode that takes a parameter from
user-space right ?
Bjorn mentioned you could write 42. My question/suggestion is why
isn't the value written a string which corresponds to the supported
modes from the EUD spec ?
"bypass" as default "debug" the mode you want to add, at a later time
you could optionally add in "control-periperhal" mode.
Makes a little more sense to me than writing just 0, 1 or 42 :) into
your store routine.
OK.
---
bod
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.
