[lkml]   [2017]   [Mar]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2 4/4] usb: dwc3: Workaround for super-speed host on dra7 in dual-role mode


Roger Quadros <> writes:
>>>> Roger Quadros <> writes:
>>>>> dra7 OTG core limits the host controller to USB2.0 (high-speed) mode
>>>>> when we're operating in dual-role.
>>>> yeah, that's not a quirk. DRA7 supports OTGv2, not OTGv3. There was no
>>>> USB3 when OTGv2 was written.
>>>> DRA7 just shouldn't use OTG core altogether. In fact, this is the very
>>>> thing I've been saying for a long time. Make the simplest implementation
>>>> possible. The dead simple, does-one-thing-only sort of implementation.
>>>> All we need for Dual-Role (without OTG extras) is some input for ID and
>>>> VBUS, then we add/remove HCD/UDC conditionally and set PRTCAPDIR.
>>> The catch is that on AM437x there is no way to get ID and VBUS events other
>>> than the OTG controller so we have to rely on the OTG controller for that. :(
>> okay, so AM437x can get OTG interrupts properly. That's fine. We can
>> still do everything we need using code that's already existing in dwc3
>> if we refactor it a bit and hook it up to the OTG IRQ handler.
>> Here's what we do:
>> * First we re-factor all necessary code around so the API for OTG/DRD
>> is resumed to calling:
>> dwc3_add_udc(dwc);
>> dwc3_del_udc(dwc);
>> dwc3_add_hcd(dwc);
>> dwc3_del_hcd(dwc);
> Why do we need these new APIs? don't these suffice?
> dwc3_gadget_init(dwc);
> dwc3_gadget_exit(dwc);
> dwc3_host_init(dwc);
> dwc3_host_exit(dwc);

well, if they do what we want, sure. They suffice.

>> the semantics of these should be easy to understand and you can
>> implement each in their respective host.c/gadget.c files.
>> * Second step is to modify our dwc3_init_mode() (or whatever that
>> function was called, sorry, didn't check) to make sure we have
>> something like:
>> case OTG:
>> dwc3_add_udc(dwc);
>> break;
>> We should *not* add HCD in this case yet.
>> * After that we add otg.c (or drd.c, no preference) and make that call
>> dwc3_add_udc(dwc) and, also, provide
>> dwc3_add_otg(dwc)/dwc3_del_otg(dwc) calls. Then patch the switch
>> statement above to:
>> case OTG:
>> dwc3_add_otg(dwc);
>> break;
>> Note that at this point, this is simply a direct replacement of
>> dwc3_add_udc() to dwc3_add_otg(). This should maintain current behavior
>> (which is starting with peripheral mode by default), but it should also
>> add support for OTG interrupts to change the mode (from an interrupt
>> thead)
>> otg_isr()
>> {
>> /* don't forget to remove preivous mode if necessary */
>> if (perimode)
>> dwc3_add_udc(dwc);
>> else
>> dwc3_add_hcd(dwc);
>> }
>> * The next patch would be to choose default conditionally based on
>> PERIMODE or whatever.
>> Of course, this is an oversimplified view of reality. You still need to
>> poke around at PRTCAPDIR, etc. But all this can, actually, be prototyped
>> using our "mode" debugfs file. Just make that call
>> dwc3_add/del_udc/hcd() apart from fiddling with PRTCAPDIR in GCTL.
> We also need to ensure that system suspend/resume doesn't break.
> Mainly if we suspend/resume with UDC removed.

right, why would it break in that case? I'm missing something...

>> Your first implementation could be just that. Refactoring what needs to
>> be refactored, then patching "mode" debugfs to work properly in that
>> case. Only add otg.c/drd.c after "mode" debugfs file is stable, because
>> then you know what needs to be taken into consideration.
>> Just to be clear, I'm not saying we should *ONLY* get the debugfs
>> interface for v4.12, I'm saying you should start with that and get that
>> stable and working properly (make an infinite loop constantly changing
>> modes and keep it running over the weekend) before you add support for
>> OTG interrupts, which could come in the same series ;-)
> Just to clarify debugfs mode behaviour.
> Currently it is just changing PRTCAPDIR. What we need to do is that if
> dr_mode == "otg", then we call dwc3_host/gadget_init/exit() accordingly as well.
> Does this make sense?

it does.

[unhandled content-type:application/pgp-signature]
 \ /
  Last update: 2017-03-31 09:47    [W:0.097 / U:24.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site