Problem with 4.6-rc2

[Mason]

On 18/04/2016 21:23, Jean Delvare wrote:

> Hi Peter, Mason,
> 
> On Mon, 18 Apr 2016 20:29:47 +0200, Mason wrote:
>> On 18/04/2016 20:06, Peter Hurley wrote:
>>
>>> On 04/18/2016 09:24 AM, Mason wrote:
>>>
>>>> I'm running into this panic. I will take a closer look tomorrow.
>>>> Any ideas?
>>>
>>> commit 8d2acdb9fc3a544ab0442634531834d6007b5467
>>> Author: Jean Delvare <jdelvare at suse.de>
>>> Date:   Mon Feb 22 09:00:39 2016 +0100
>>>
>>>     serial: 8250: Add hardware dependency to RT288X option
>>>     
>>>     Kconfig option SERIAL_8250_RT288X seems to be only relevant on MIPS
>>>     platforms, so do not present it on other architectures, unless
>>>     build-testing.
>>>     
>>>     Signed-off-by: Jean Delvare <jdelvare at suse.de>
>>>     Cc: Mans Rullgard <mans at mansr.com>
>>>     Cc: Jiri Slaby <jslaby at suse.com>
>>>     Acked-by: John Crispin <blogic at openwrt.org>
>>>     Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
>>>
>>>
>>> Not sure why Greg picked this up over my objections though
> 
> Greg applied v1 of my patch. In v2 I added ARCH_TANGO as a possible
> dependency, but Greg did pick the update. Mason, is your target machine
> an ARCH_TANGO machine, or something else?

Correct, ARCH_TANGO.
http://lxr.free-electrons.com/source/arch/arm/mach-tango/Kconfig

>> Peter,
>>
>> Thanks for pointing out the problem.
> 
> Mason, did you check if reverting this commit and re-enabling
> SERIAL_8250_RT288X actually solves your problem?

I will test tomorrow. But I'm quite confident that enabling
SERIAL_8250_RT288X will make the problem go away (see below).

>> My ARM-based SoC uses this hardware (Palmchip BK-3103) and it
>> now panics on boot.
>>
>> Can we revert 8d2acdb9fc3a in time for v4.6?
> 
> If not selecting SERIAL_8250_RT288X results in a crash at boot on some
> systems, then reverting my commit is not the proper fix. Even after
> reverting, you can still omit selecting the option, and get the same
> crash. In other words, my commit is not introducing the crash, it must
> have been there lurking before.

I wanted to have
select SERIAL_8250_RT288X if SERIAL_8250
in my platform Kconfig, but Arnd shot that down :-(
(What good is a SoC without a console?)

http://thread.gmane.org/gmane.linux.ports.arm.kernel/444131/focus=444197

"Picking SERIAL_8250 but not SERIAL_8250_RT288X makes the kernel
panic. Doesn't that qualify for selecting it?"

The problem has existed for a while.

> Whatever code crashes in this case should be made more robust to
> properly deal with the situation. Or if it is too much work or too ugly
> (not being familiar with the code, I have no idea), then we could
> finally go with Peter's earlier proposal of dropping the
> SERIAL_8250_RT288X option altogether and unconditionally including the
> code in question. In fact I think Peter was supposed to send a patch
> doing exactly that.

Regards.