linux-kernel - Re: [PATCH v8 8/8] clk: Add KUnit tests for clks registered with struct clk_parent

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Message-ID: <dcd8894f-1eb6-4b5c-9e6f-f6e584c601d2@roeck-us.net>
Date: Fri, 27 Sep 2024 09:19:30 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Stephen Boyd <sboyd@...nel.org>
Cc: 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>,
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Rob Herring <robh@...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>,
	Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH v8 8/8] clk: Add KUnit tests for clks registered with
 struct clk_parent_data

Copying devicetree maintainers.

On Thu, Sep 26, 2024 at 09:39:38PM -0700, Guenter Roeck wrote:
> On Thu, Sep 26, 2024 at 09:14:11PM -0700, Guenter Roeck wrote:
> > Hi Stephen,
> > 
> > On Thu, Jul 18, 2024 at 02:05:07PM -0700, Stephen Boyd wrote:
> > > Test that clks registered with 'struct clk_parent_data' work as
> > > intended and can find their parents.
> > > 
> > 
> > When testing this on arm64, I see the error below. The error is only
> > seen if I boot through efi, i.e., with "-bios QEMU_EFI-aarch64.fd"
> > qemu parameter.
> > 
> > Any idea what might cause the problem ?
> > 
> I noticed that the new overlay tests fail as well, also with "path '/' not
> found".
> 
> [Maybe] answering my own question: I think the problem may be that there
> is no devicetree file and thus no devicetree root when booting through
> efi (in other words, of_root is NULL). Would it make sense to skip the
> tests in that case ?
> 

The problem is that of_root is not initialized in arm64 boots if ACPI
is enabled.

>From arch/arm64/kernel/setup.c:setup_arch():

	if (acpi_disabled)
		unflatten_device_tree();		// initializes of_root

ACPI is enabled if the system boots from EFI. This also affects
CONFIG_OF_KUNIT_TEST, which explicitly checks if of_root exists and
fails the test if it doesn't. 

I think those tests need to add a check for this condition, or affected
machines won't be able to run those unit tests. The obvious solution would
be to check if of_root is set, but then the associated test case in
CONFIG_OF_KUNIT_TEST would not make sense.

Any suggestions ?

Thanks,
Guenter