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

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Message-ID: <879831a8-2039-4cdb-bce2-aefdeb7ab25f@linuxfoundation.org>
Date: Sat, 28 Sep 2024 11:54:46 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Guenter Roeck <linux@...ck-us.net>, 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>,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v8 8/8] clk: Add KUnit tests for clks registered with
 struct clk_parent_data

On 9/28/24 11:31, Guenter Roeck wrote:
> On 9/27/24 17:08, Guenter Roeck wrote:
>> On 9/27/24 13:45, Shuah Khan wrote:
>>> On 9/27/24 10:19, Guenter Roeck wrote:
>>>> 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 ?
>>>>
>>>
>>> Would it work if these tests check if acpi_disabled and skip if it isn't
>>> disabled? It might be low overhead condition to check from these tests.
>>>
>>> acpi_disabled is exported:
>>>
>>> arch/arm64/kernel/acpi.c:EXPORT_SYMBOL(acpi_disabled);
>>> arch/loongarch/kernel/acpi.c:EXPORT_SYMBOL(acpi_disabled);
>>> arch/riscv/kernel/acpi.c:EXPORT_SYMBOL(acpi_disabled);
>>> arch/x86/kernel/acpi/boot.c:EXPORT_SYMBOL(acpi_disabled);
>>>
>>
>> I don't think that would work. Looking through the use of acpi_init,
>> I don't think that of_root is always NULL when acpi_init is false; that
>> just happens to be the case on arm64 when booting through efi.
>> However, even arm64 has the following code.
>>
>>          if (acpi_disabled)
>>                  psci_dt_init();
>>          else
>>                  psci_acpi_init();
>>
>> While psci_dt_init() doesn't set of_root, it does try to do a devicetree
>> match. So there must be some other condition where acpi_disabled is set
>> but of_root is set anyway. I just have not found that code path.
>>
> 
> I ended up disabling all affected unit tests for arm64. I'll do the same
> for other architectures if I encounter the problem there as well.
> 
> Unfortunately that includes all clock unit tests because the tests requiring
> devicetree support can not be enabled/disabled separately, but that can't be
> helped and is still better than "mandatory" failures.
> 

I am hoping Stephen will have a solution for this problem. In the meantime,
I will look into this to see if we can find a check that works.

thanks,
-- Shuah