Re: [Buildroot] [PATCH v5 2/6] board/raspberrypicm4io: enable RTC and USB overlays

["Yann E. MORIN" <yann.morin.1998@free.fr>]

On 2021-10-17 22:54 +0200, Peter Seiderer spake thusly:
> On Sun, 17 Oct 2021 22:27:17 +0200, "Yann E. MORIN" <yann.morin.1998@free.fr> wrote:
> > On 2021-09-21 22:21 +0200, Peter Seiderer spake thusly:
> > > - add RTC and USB dtoverlay entries to config_cm4io.txt
> > Why specifically the RTC and USB? And why only on the CM, and not the
> > other boards?
> The config is not for the CM4 standalone, but specific to the
> CM4 IO Board, equipped (as the only RPi original one) with an
> RTC chip....

Ah, OK, that makes sense, then.

> > IIRC, dwc2 is an OTG chip, too, and it is also wired on the rpi0. Well,
> > by experience, I know that the rpi0 *can* do USB slave/OTG.
> And as far as I know the USB is enabled with all RPi's with
> exception of the CM4: 'The  USB  interface  is  disabled  to  save  power  by
> default  on  the  CM4' (see [1] page 5)
> 
> According to [2]:
> 
> 	Name:   dwc-otg
> 	Info:   Selects the dwc_otg USB controller driver which has fiq support. This
> 	        is the default on all except the Pi Zero which defaults to dwc2.
> 	Load:   dtoverlay=dwc-otg
> 	Params: <None>
> 
> 
> 	Name:   dwc2
> 	Info:   Selects the dwc2 USB controller driver
> 	Load:   dtoverlay=dwc2,<param>=<val>
> 	Params: dr_mode                 Dual role mode: "host", "peripheral" or "otg"
> 
> 	        g-rx-fifo-size          Size of rx fifo size in gadget mode
> 
> 	        g-np-tx-fifo-size       Size of non-periodic tx fifo size in gadget
> 	                                mode


> Would interpret 'defaults to dwc2' on Pi Zero as enabled by default...

Yes, it is enabled by default, as a host-only controller, not OTG, which
has to be explictly requested.

Regards,
Yann E. MORIN.

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