[PATCH] event: add an event for livetree fixups

[Caleb Connolly]

On 12/04/2024 20:45, Tom Rini wrote:
> On Fri, Apr 12, 2024 at 08:04:02PM +0100, Caleb Connolly wrote:
> 
>> Introduce a new EVT_OF_LIVE event to allow for the livetree to be
>> modified before dm_init_and_scan(). Boards can perform fixups here to
>> handle incompatibilities between U-Boot drivers and upstream DT.
>>
>> This will be used by Qualcomm platforms in future patches to enable
>> setting the dr_mode property if the board doesn't provide one. This has to be
>> set before dm_init_and_scan() is called as this property effects the binding of
>> drivers.
> 
> This doesn't quite explain why the answer isn't "fix the device tree
> source" and instead "perform a live fixup". Thanks.

Hi Tom,

I think the specifics here that make this difficult is that on some
Qualcomm boards there is only one USB controller, which can be muxed
either to a type-c port or to a USB hub via a DIP switch (the state of
which cannot easily be read out).

The DT should therefore either not set dr_mode or set it to OTG. This is
what Linux expects (and it can do proper role detection).

The dwc3 driver in U-Boot currently doesn't have the ability to
dynamically mode switch, this is something I'd like to add (as it would
let us easily flash these boards from U-Boot as well as boot from USB or
ethernet), but in the mean time the only way to get these boards into
host mode (which is the preferred default) is to modify the DT in a way
that breaks Linux.

Hence the proposal in this patch.

If this is ok for you then I'll re-send with this additional context in
the commit description.

Thanks and regards,

-- 
// Caleb (they/them)