linux-kernel - Re: [PATCH v6] amba: Remove deferred device addition

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Date:   Tue, 9 Aug 2022 18:34:40 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Russell King <linux@...linux.org.uk>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        patches@...linux.org.uk, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] amba: Remove deferred device addition

On 8/9/22 17:42, Saravana Kannan wrote:
> On Tue, Aug 9, 2022 at 3:30 AM Guenter Roeck <linux@...ck-us.net> wrote:
>>
>> Hi,
>>
>> On Wed, Jul 27, 2022 at 11:19:35AM -0700, Saravana Kannan wrote:
>>> The uevents generated for an amba device need PID and CID information
>>> that's available only when the amba device is powered on, clocked and
>>> out of reset. So, if those resources aren't available, the information
>>> can't be read to generate the uevents. To workaround this requirement,
>>> if the resources weren't available, the device addition was deferred and
>>> retried periodically.
>>>
>> ...
>>
>> This patch results in a large number of crashes in various qemu
>> emulations. Crash and bisect logs below. Reverting this patch
>> fixes the problem.
> 
> Hey Guenter,
> 
> Thanks for the report. I'm kinda surprised because I had a pl011 probe
> successfully in my local testing.
> 

Maybe it only happens with qemu emulations, or with certain configurations.

> I'm wondering if you are having an interaction with some other changes I made.
> Can you try pulling this series in and see if it helps?
> 
> https://lore.kernel.org/lkml/20220727185012.3255200-1-saravanak@google.com/
> 
>> Additional information: The decoded stack trace suggests that the
>> "id" parameter of pl011_probe() may be NULL.
> 
> That's strange! I'll take a closer look once you confirm that the
> series above doesn't help.
> 

That series does not make a difference.

Guenter