linux-kernel - Re: [PATCH 1/2] MIPS: Allow MIPS32R2 kernel to run on P5600 and M5150

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Message-Id: <5CC33034-4AF3-4522-9942-8BCCEF1086AE@flygoat.com>
Date:   Tue, 30 May 2023 14:10:04 +0100
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     "Maciej W. Rozycki" <macro@...am.me.uk>
Cc:     Paul Cercueil <paul@...pouillou.net>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Subject: Re: [PATCH 1/2] MIPS: Allow MIPS32R2 kernel to run on P5600 and M5150



> 2023年5月30日 13:16，Maciej W. Rozycki <macro@...am.me.uk> 写道：
> 
> On Tue, 30 May 2023, Jiaxun Yang wrote:
> 
>>> Sure, but this change is not needed for it.  You just need to declare 
>>> which ISA revisions your platform supports and leave `__get_cpu_type' 
>>> alone.  It has worked like that for a decade now.
>> 
>> I’m afraid it won’t work as you expected.
>> 
>> Actually I ran into a problem that `case CPU_P5600` in c-r4k.c is optimised out
>> by compiler, because the codepath is marked as unreachable.
> 
> Maybe there's a bug elsewhere then.  Send me your .config and I'll try to 
> reproduce it.

Ok I see the problem, after applying patch 2 the issue is gone.
So actually only patch 2 is necessary.

The unreachable mark here leads gcc to generate some confusing code
and I misread it.

Sorry for the noise.

Thanks
- Jiaxun

> 
>  Maciej