Re: [PATCH anybus v3 1/6] misc: support the Arcx anybus bridge

[Sven Van Asbroeck <thesven73@gmail.com>]

On Tue, Nov 6, 2018 at 8:58 AM Rob Herring <robh@kernel.org> wrote:

> It doesn't really sound like the host should be in DT. The bridge
> should register itself as an anybus provider and that should in turn
> enable the anybus host protocol.

Very good point. Just to make sure we're on the same page, could you point
me to a relevant example where something registers as a provider?

v1 of this patch did not have the host in DT. The host just required platform
data with a regmap and a reset (the interrupt was passed via resources):

struct anybuss_host_pdata {
    struct regmap *regmap;
    void (*reset)(struct device *dev, bool reset);
};

But there were problems with this approach.

The review feedback told me that my self-rolled reset callback should really
be a reset controller. I looked for ways to pass a handle to a reset controller
via platform data. This has recently been introduced via:

reset_controller_add_lookup()

This binds a client device to a reset controller, without using the devicetree,
so the device can grab its controller via (devm_)reset_control_get*. Great!
But... to make the binding, you have to specify the full device names of the
controllers and client devices. See this example from psc-da850.c:

static struct reset_control_lookup da850_psc0_reset_lookup_table[] = {
    RESET_LOOKUP("da850-psc0", 15, "davinci-rproc.0", NULL),
};

I very quickly found myself in ida_simple_get() hell, trying to second-guess
what the devices I was creating, would be called !

So instead I put the host in DT, then I could easily connect the reset
controller. This also greatly simplified the bridge driver, a lot of boilerplate
would simply disappear.

Suggestions are very welcome :)

Sven