linux-kernel - Re: [PATCH v2 1/1] serial: core: Fix serial_base_match() after fixing controller port name

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Date:   Sat, 5 Aug 2023 08:50:48 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        kernel test robot <oliver.sang@...el.com>
Subject: Re: [PATCH v2 1/1] serial: core: Fix serial_base_match() after fixing
 controller port name

On 8/5/23 04:48, Tony Lindgren wrote:
> * Guenter Roeck <linux@...ck-us.net> [230805 10:50]:
>> On 8/4/23 21:49, Tony Lindgren wrote:
>>> * Guenter Roeck <linux@...ck-us.net> [230804 21:42]:
>>>> kobject: kobject_add_internal failed for serial8250.0:0.0 with -EEXIST, don't try to register things with the same name in the same directory.
>>>> serial8250 serial8250.0: unable to register port at index 1 (IO2f8 MEM0 IRQ3): -17
>>>> sysfs: cannot create duplicate filename '/devices/platform/serial8250.0/serial8250.0:0/serial8250.0:0.0'
>>>
>>> The issue above should be fixed with commit:
>>>
>>> bbb4abb1bcfb ("serial: 8250: Reinit port_id when adding back serial8250_isa_devs")
>>>
>>
>> No. I tested the tip of tty-linus (v6.5-rc4-9-gdfe2aeb226fd) which includes
>> above commit, but still see the problem. sparc images also still stall after
>> the "cannot create duplicate filename" message.
>> I bisected the sparc problem - it also bisects to commit d962de6ae51f.
>>
>> The problem affects all mips boot tests, all sparc boot tests, as well as
>> arm sx1, ppc bamboo and sam460ex emulations. As far as I can see, those
>> call serial8250_register_8250_port() without calling  serial8250_setup_port()
>> and thus don't set port_id. I am only testing a few of those, so I strongly
>> suspect that all similar callers of serial8250_register_8250_port() are
>> affected (i.e., almost all of them) if they register more than one serial port.
> 
> OK thanks for explaining. So we need to initialize port->port_id for the
> multi-port instances to avoid being stuck with the port->line index. I'll
> take a look.
> 
> I wonder if we should just revert d962de6ae51f for now. It needs to be
> tested to see if something else also needs reverting though.
> 

It is actually more complicated like that. Adding some debug into, I get the following
from a mips boot. Turns out that serial8250_setup_port() is actually called.

...
####### serial8250_setup_port: index 0
####### serial8250_setup_port: index 0 returning 819a5ab8
####### serial8250_setup_port: index 1
####### serial8250_setup_port: index 1 returning 819a5d20
####### serial8250_setup_port: index 2
####### serial8250_setup_port: index 2 returning 819a5f88
####### serial8250_setup_port: index 3
####### serial8250_setup_port: index 3 returning 819a61f0
...
#### serial8250_register_8250_port: uart=819a5ab8
#### serial8250_register_8250_port: uart=819a5ab8 port_id=0 line=0
...
#### serial8250_register_8250_port: uart=819a5d20
#### serial8250_register_8250_port: uart=819a5d20 port_id=1 line=1
sysfs: cannot create duplicate filename '/devices/platform/serial8250.0/serial8250.0:0/serial8250.0:0.0'

So line and port_id are both set, but the created sysfs attribute
is still duplicate. I'll do some more debugging.

Guenter