linux-kernel - Re: [PATCH v4 00/10] clk: Add kunit tests for fixed rate and parent data

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Date: Wed, 15 May 2024 17:08:47 -0500
From: Rob Herring <robh@...nel.org>
To: Stephen Boyd <sboyd@...nel.org>
Cc: David Gow <davidgow@...gle.com>, Michael Turquette <mturquette@...libre.com>, 
	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org, 
	patches@...ts.linux.dev, kunit-dev@...glegroups.com, 
	linux-kselftest@...r.kernel.org, devicetree@...r.kernel.org, 
	Brendan Higgins <brendan.higgins@...ux.dev>, Rae Moar <rmoar@...gle.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J . Wysocki" <rafael@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, Daniel Latypov <dlatypov@...gle.com>, 
	Christian Marangi <ansuelsmth@...il.com>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Maxime Ripard <maxime@...no.tech>
Subject: Re: [PATCH v4 00/10] clk: Add kunit tests for fixed rate and parent data

On Wed, May 15, 2024 at 4:15 PM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting Rob Herring (2024-05-15 06:06:09)
> > On Tue, May 14, 2024 at 4:29 PM Stephen Boyd <sboyd@...nel.org> wrote:
> > >
> > > powerpc doesn't mark the root node with OF_POPULATED_BUS. If I set that
> > > in of_platform_default_populate_init() then the overlays can be applied.
> > >
> > > ---8<----
> > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > > index 389d4ea6bfc1..fa7b439e9402 100644
> > > --- a/drivers/of/platform.c
> > > +++ b/drivers/of/platform.c
> > > @@ -565,6 +565,10 @@ static int __init of_platform_default_populate_init(void)
> > >                                 of_platform_device_create(node, buf, NULL);
> > >                 }
> > >
> > > +               node = of_find_node_by_path("/");
> > > +               if (node)
> > > +                       of_node_set_flag(node, OF_POPULATED_BUS);
> >
> > I think you want to do this in of_platform_bus_probe() instead to
> > mirror of_platform_populate(). These are supposed to be the same
> > except that 'populate' only creates devices for nodes with compatible
> > while 'probe' will create devices for all child nodes. Looks like we
> > are missing some devlink stuff too. There may have been some issue for
> > PPC with it.
>
> Got it. So this patch?
>
> ---8<---
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 389d4ea6bfc1..acecefcfdba7 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -421,6 +421,7 @@ int of_platform_bus_probe(struct device_node *root,
>         if (of_match_node(matches, root)) {
>                 rc = of_platform_bus_create(root, matches, NULL, parent, false);
>         } else for_each_child_of_node(root, child) {
> +               of_node_set_flag(root, OF_POPULATED_BUS);

No, the same spot as of_platform_populate has it. I guess this would
be the same, but no reason to do this in the for_each_child_of_node
loop...

>                 if (!of_match_node(matches, child))
>                         continue;
>                 rc = of_platform_bus_create(child, matches, NULL, parent, false);
>
>
> This doesn't work though. I see that prom_init() is called, which
> constructs a DTB and flattens it to be unflattened by
> unflatten_device_tree(). The powerpc machine type used by qemu is
> PLATFORM_PSERIES_LPAR. It looks like it never calls
> of_platform_bus_probe() from the pseries platform code.

Huh. Maybe pseries doesn't have any platform devices?

Ideally, we'd still do it in of_platform_default_populate_init(), but
if you look at the history, you'll see that broke some PPC boards
(damn initcall ordering).

> What about skipping the OF_POPULATED_BUS check, or skipping the check
> when the parent is the root node? This is the if condition that's
> giving the headache.

I don't think we should just remove it, but a root node check seems fine.

Rob