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

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Message-Id: <9BBD5835-ACD8-48BD-AED9-E23473237FAD@flygoat.com>
Date:   Tue, 30 May 2023 13:57:39 +0100
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     "Maciej W. Rozycki" <macro@...am.me.uk>,
        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 13:51，Serge Semin <fancer.lancer@...il.com> 写道：
> 
> On Tue, May 30, 2023 at 03:41:30PM +0300, Serge Semin wrote:
>> On Tue, May 30, 2023 at 01:16:32PM +0100, Maciej W. Rozycki wrote:
>>> 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.
>> 
>> I may have misunderstood something, but it seems like there is no such
>> problem on my P5600 system:
>> 
>> [fancer@...ilestation] kernel $ grep -r P5600 -B2 -A2 arch/mips/mm/c-r4k.c 
>>        case CPU_1004K:
>>        case CPU_INTERAPTIV:
>>        case CPU_P5600:
>>        case CPU_PROAPTIV:
>>        case CPU_M5150:
>> --
>>        case CPU_P6600:
>>        case CPU_M6250:
>>                pr_info("MIPS P5600 is here\n");
>>                if (!(read_c0_config7() & MIPS_CONF7_IAR) &&
>>                    (c->icache.waysize > PAGE_SIZE))
>> 
>> Log:
>> [    0.000000] Linux version 6.4.0-rc1-bt1-00235-gf9efd6b74b12-dirty (fancer@...ilestation) (mipsel-baikal-linux-gcc (GCC) 7.3.0, GNU ld (GNU Binutils) 2.30.0.20180208) #1
>> 275 SMP PREEMPT Tue May 30 15:30:48 MSK 2023
>> [    0.000000] CPU0 revision is: 0001a830 (MIPS P5600)
>> [    0.000000] FPU revision is: 30f30320
>> [    0.000000] MSA revision is: 00000320
>> ...
>> [    0.000000] VPE topology {1,1} total 2
>> [    0.000000] MIPS P5600 is here
>> ...
> 
> Here is the CPU-related kernel configs:
> root@...t2:~# cat /proc/config.gz | gunzip | grep CPU_MIPS
> # CONFIG_CPU_MIPS32_R2 is not set
> # CONFIG_CPU_MIPS32_R5 is not set
> # CONFIG_CPU_MIPS32_3_5_FEATURES is not set
> CONFIG_CPU_MIPS32_R5_FEATURES=y
> CONFIG_CPU_MIPS32_R5_XPA=y
> CONFIG_SYS_HAS_CPU_MIPS32_R2=y
> CONFIG_SYS_HAS_CPU_MIPS32_R3_5=y
> CONFIG_SYS_HAS_CPU_MIPS32_R5=y
> CONFIG_CPU_MIPS32=y
> CONFIG_CPU_MIPSR5=y
> CONFIG_CPU_MIPSR2_IRQ_VI=y
> CONFIG_CPU_MIPSR2_IRQ_EI=y

I was trying to run kernel compiled with CONFIG_CPU_MIPS32_R2 on P5600.

Thanks
- Jiaxun

> 
> -Serge(y)
> 
>> 
>> -Serge(y)
>> 
>>> 
>>>  Maciej