linux-kernel - Re: [PATCH 03/17] base: fix order of OF initialization

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Message-ID: <5938C957.2030005@gmail.com>
Date:   Wed, 7 Jun 2017 20:49:43 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Wesley Terpstra <wesley@...ive.com>,
        Mark Rutland <mark.rutland@....com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
        Albert Ou <albert@...ive.com>, patches@...ups.riscv.org,
        Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH 03/17] base: fix order of OF initialization

On 06/07/17 11:39, Wesley Terpstra wrote:
> It was a while ago that I debugged this. I already reported this bug
> to Benjamin Herrenschmidt (now in CC), and I believe he has a patch of
> his own to fix the same issue.
> 
> As I understand it, of_core_init sets up the OF entries in
> /sys/firmware/devicetree. During platform bringup, when the system
> describes the cpu + cache hierarchy, it also makes an of_node symlink
> into that directory. However, if it doesn't exist yet, you get the
> warning.
> 
> # ls -l /sys/devices/system/cpu/cpu3/of_node
> lrwxrwxrwx    1 root     root             0 Jan  1 00:00
> /sys/devices/system/cpu/cpu3/of_node ->
> ../../../../firmware/devicetree/base/cpus/cpu@3
> 
> On Wed, Jun 7, 2017 at 2:35 AM, Mark Rutland <mark.rutland@....com> wrote:
>> On Wed, Jun 07, 2017 at 09:07:20AM +0200, Geert Uytterhoeven wrote:
>>> CC devicetree folks
>>>
>>> On Wed, Jun 7, 2017 at 12:59 AM, Palmer Dabbelt <palmer@...belt.com> wrote:
>>>> From: "Wesley W. Terpstra" <wesley@...ive.com>
>>>>
>>>> This fixes: [    0.010000] cpu cpu0: Error -2 creating of_node link
>>>> ... which you get for every CPU on all architectures with a OF cpu/ node.
>>
>> I take it this means a /cpus node? Or the /cpus/cpu@* nodes?
>>
>> I'm not seeing this on arm64 when booting v4.12-rc4 with DT, so clearly
>> this doesn't affect all such architectures.
>>
>> What path are these errors happening in?

On the surface, the patch looks reasonable.  But it is not obvious to me why
the error message is occurring.  I would like to understand the cause before
saying the patch is good.

What kernel version is showing the error?  For a specific architecture
(the patch lists 'riscv, nios, etc'), which config and device tree source?

And again, what is the calling path?

- Frank

>>
>> Thanks,
>> Mark.
>>
>>>>
>>>> This affects riscv, nios, etc.
>>>>
>>>> Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
>>>> ---
>>>>  drivers/base/init.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/base/init.c b/drivers/base/init.c
>>>> index 48c0e220acc0..0dcd17e561d0 100644
>>>> --- a/drivers/base/init.c
>>>> +++ b/drivers/base/init.c
>>>> @@ -31,9 +31,9 @@ void __init driver_init(void)
>>>>         /* These are also core pieces, but must come after the
>>>>          * core core pieces.
>>>>          */
>>>> +       of_core_init();
>>>>         platform_bus_init();
>>>>         cpu_dev_init();
>>>>         memory_dev_init();
>>>>         container_dev_init();
>>>> -       of_core_init();
>>>>  }
>>>> --
>>>> 2.13.0
>>> --
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>