From: Strontium <strntydog@gmail.com>
To: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>,
"Maciej W. Rozycki" <macro@orcam.me.uk>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Wei Li <liwei391@huawei.com>,
Tiezhu Yang <yangtiezhu@loongson.cn>,
linux-mips@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH] MIPS: add support for buggy MT7621S core detection
Date: Fri, 25 Jun 2021 17:54:39 +0700 [thread overview]
Message-ID: <0099b98c-3774-c5c0-7b1b-1f9e61e0574f@gmail.com> (raw)
In-Reply-To: <CALCv0x0wQ9DJUVEPXCgbBFQHjqNCfSYLFkU0Md2zjJ4XfydhXg@mail.gmail.com>
On 8/4/21 1:49 am, Ilya Lipnitskiy wrote:
> On Wed, Apr 7, 2021 at 6:49 AM Maciej W. Rozycki <macro@orcam.me.uk> wrote:
>> On Mon, 5 Apr 2021, Ilya Lipnitskiy wrote:
>>
>>> Thanks for the comments. Including asm/bugs.h in asm/mips-cps.h led to
>>> some circular dependencies when I tried it, but I will try again based
>>> on your feedback - indeed it would be much cleaner to have this logic
>>> in mips_cps_numcores. The only wrinkle is that mips_cps_numcores may
>>> return a different value on MT7621 after the cores have started due to
>>> CPULAUNCH flags changing, but nobody calls mips_cps_numcores later
>>> anyway, so it's a moot point today. I will clean up the change and
>>> resend.
>> Hmm, I don't know this system, but by the look of the code it queries
>> launch[2], which I gather refers to the VPE #0 of an inexistent core #1,
>> so why would the structure change given that there is no corresponding
>> silicon?
> The structure would change only on the dual-core flavor of MT7621, the
> single-core would always report 1 core, but on the dual-core, if
> somebody were to call mips_cps_numcores after the second core had
> already started, mips_cps_numcores would return 1 instead of 2. I
> think it may be feasible to fix it by checking other flags, but there
> is no use case for that today, so I'd rather keep this hacky logic to
> a minimum.
>
> Ilya
>
>
Actually, I am currently struggling with a side effect of this approach
in the original OpenWrt version of this method, although i think this
version will suffer from the same effect.
When you kexec the kernel from a previously running kernel, it only
detects a single core. I am about to disable it entirely, as i really
need to be able to run kexec on a MT7621 platform.
I have instrumented the code with some debug to prove it is the case:
Boot from u-boot:
[ 0.000000] nclusters = 1
[ 0.000000] VPE topology
[ 0.000000] cl = 0
[ 0.000000] {
[ 0.000000] ncores = 2
[ 0.000000] cpulaunch.pc = 000000ff
[ 0.000000] cpulaunch.gp = 0000ff00
[ 0.000000] cpulaunch.sp = 0000ffff
[ 0.000000] cpulaunch.a0 = 08000800
[ 0.000000] cpulaunch.flags = 00000020
[ 0.000000] plat_cpu_core_present(0) = true
[ 0.000000] core_vpes = 2
[ 0.000000] 2
[ 0.000000] cpulaunch.pc = 000000ff
[ 0.000000] cpulaunch.gp = 0000ff00
[ 0.000000] cpulaunch.sp = 0000ffff
[ 0.000000] cpulaunch.a0 = 08000800
[ 0.000000] cpulaunch.flags = 00000020
[ 0.000000] plat_cpu_core_present(1) = true
[ 0.000000] core_vpes = 2
[ 0.000000] ,2} total 4
Boot from kexec:
[ 0.000000] nclusters = 1
[ 0.000000] VPE topology
[ 0.000000] cl = 0
[ 0.000000] {
[ 0.000000] ncores = 2
[ 0.000000] cpulaunch.pc = 00000000
[ 0.000000] cpulaunch.gp = 00000000
[ 0.000000] cpulaunch.sp = 00000000
[ 0.000000] cpulaunch.a0 = 00000000
[ 0.000000] cpulaunch.flags = 00000000
[ 0.000000] plat_cpu_core_present(0) = true
[ 0.000000] core_vpes = 2
[ 0.000000] 2
[ 0.000000] cpulaunch.pc = 00000000
[ 0.000000] cpulaunch.gp = 00000000
[ 0.000000] cpulaunch.sp = 00000000
[ 0.000000] cpulaunch.a0 = 00000000
[ 0.000000] cpulaunch.flags = 00000000} total 2
Steven
next prev parent reply other threads:[~2021-06-25 10:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-03 6:19 [PATCH] MIPS: add support for buggy MT7621S core detection Ilya Lipnitskiy
2021-04-06 1:22 ` Maciej W. Rozycki
2021-04-06 1:54 ` Ilya Lipnitskiy
2021-04-07 13:49 ` Maciej W. Rozycki
2021-04-07 18:49 ` Ilya Lipnitskiy
2021-06-25 10:54 ` Strontium [this message]
2021-04-06 4:23 ` [PATCH v2] " Ilya Lipnitskiy
2021-04-07 13:52 ` Maciej W. Rozycki
2021-04-07 20:07 ` [PATCH v3] " Ilya Lipnitskiy
2021-04-12 15:03 ` Thomas Bogendoerfer
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