Re: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev

Peter Chen
2016-09-07T09:29:13Z

On Wed, Sep 07, 2016 at 10:52:46AM +0200, Arnd Bergmann wrote:
> On Wednesday, September 7, 2016 3:44:28 PM CEST Peter Chen wrote:
> >
> > The pre-condition of DT function at USB HCD core works is the host
> > controller device has of_node, since it is the root node for USB tree
> > described at DT. If the host controller device is not at DT, it needs
> > to try to get its of_node, the chipidea driver gets it through its
> > parent node [1]
>
> >
> > [1] https://lkml.org/lkml/2016/8/8/119
> >
>
> Ah, this is what I was referring to in the other mail.
>
> However, the way you set the of_node might be dangerous too:
> We should generally not have two platform_device structures with
> the same of_node pointer, most importantly it may cause the
> child device to be bound to the same driver as the parent
> device since the probing is done by compatible string.
>
> As you tested it successfully, it must work at the moment on your
> machine, but it could easily break depending on deferred probing
> or module load order.
>

Currently, I work around above problems by setting core device of_node
as NULL at both probe error path and platform driver .remove routine.

I admit it is not a good way, but if we only have of_node at device's
life periods after probe, it seems ok currently. It is hard to create
of_node dynamically when create device, and keep some contents
of parent's of_node, and some are not.

--

Best Regards,
Peter Chen