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Subject: Re: [PATCH 1/2] MIPS: Allow MIPS32R2 kernel to run on P5600 and M5150
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
In-Reply-To: <20230530125100.bd626syvkbfv7zhv@mobilestation>
Date:   Tue, 30 May 2023 13:57:39 +0100
Cc:     "Maciej W. Rozycki" <macro@orcam.me.uk>,
        Paul Cercueil <paul@crapouillou.net>,
        "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
        linux-kernel@vger.kernel.org,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>
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Message-Id: <9BBD5835-ACD8-48BD-AED9-E23473237FAD@flygoat.com>
References: <20230529135245.4085-1-jiaxun.yang@flygoat.com>
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 <20230530125100.bd626syvkbfv7zhv@mobilestation>
To:     Serge Semin <fancer.lancer@gmail.com>
Precedence: bulk


> 2023=E5=B9=B45=E6=9C=8830=E6=97=A5 13:51=EF=BC=8CSerge Semin =
<fancer.lancer@gmail.com> =E5=86=99=E9=81=93=EF=BC=9A
>=20
> 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:
>>>=20
>>>>> Sure, but this change is not needed for it.  You just need to =
declare=20
>>>>> which ISA revisions your platform supports and leave =
`__get_cpu_type'=20
>>>>> alone.  It has worked like that for a decade now.
>>>>=20
>>>> I=E2=80=99m afraid it won=E2=80=99t work as you expected.
>>>>=20
>>>> 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.
>>>=20
>>> Maybe there's a bug elsewhere then.  Send me your .config and I'll =
try to=20
>>> reproduce it.
>>=20
>> I may have misunderstood something, but it seems like there is no =
such
>> problem on my P5600 system:
>>=20
>> [fancer@mobilestation] kernel $ grep -r P5600 -B2 -A2 =
arch/mips/mm/c-r4k.c=20
>>        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))
>>=20
>> Log:
>> [    0.000000] Linux version 6.4.0-rc1-bt1-00235-gf9efd6b74b12-dirty =
(fancer@mobilestation) (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
>> ...
>=20
> Here is the CPU-related kernel configs:
> root@msbt2:~# 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=3Dy
> CONFIG_CPU_MIPS32_R5_XPA=3Dy
> CONFIG_SYS_HAS_CPU_MIPS32_R2=3Dy
> CONFIG_SYS_HAS_CPU_MIPS32_R3_5=3Dy
> CONFIG_SYS_HAS_CPU_MIPS32_R5=3Dy
> CONFIG_CPU_MIPS32=3Dy
> CONFIG_CPU_MIPSR5=3Dy
> CONFIG_CPU_MIPSR2_IRQ_VI=3Dy
> CONFIG_CPU_MIPSR2_IRQ_EI=3Dy

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

Thanks
- Jiaxun

>=20
> -Serge(y)
>=20
>>=20
>> -Serge(y)
>>=20
>>>=20
>>>  Maciej