linux-kernel - Re: [PATCH] MIPS: vpe-mt: provide a default 'physical

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Message-ID: <3c0fd19c-693e-465b-bc79-3a0cd4c71319@infradead.org>
Date:   Fri, 17 Feb 2023 12:04:29 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Philippe Mathieu-Daudé <philmd@...aro.org>,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Dengcheng Zhu <dzhu@...ecomp.com>,
        John Crispin <john@...ozen.org>, linux-mips@...r.kernel.org,
        Qais Yousef <qyousef@...alina.io>
Subject: Re: [PATCH] MIPS: vpe-mt: provide a default 'physical_memsize'



On 2/17/23 03:57, Thomas Bogendoerfer wrote:
> On Wed, Feb 15, 2023 at 10:59:35PM -0800, Randy Dunlap wrote:
>>> I agree this is where this variable has be be declared / initialized,
>>> but having this dependent on CONFIG_MIPS_MALTA/CONFIG_LANTIQ machines
>>> doesn't seem right.
>>
>> So far I have been able to consolidate the LANTIQ code into a general
>> patch, but not MALTA.
> 
> if I didn't miss something physical_memory is always 0 for LANTIQ 
> and something for MALTA depending on command line/DT. Now
> 
> arch/mips/kernel/vpe-mt.c contains
> 
>         /*
>          * The sde-kit passes 'memsize' to __start in $a3, so set something
>          * here...  Or set $a3 to zero and define DFLT_STACK_SIZE and
>          * DFLT_HEAP_SIZE when you compile your program
>          */
>         mttgpr(6, v->ntcs);
>         mttgpr(7, physical_memsize);
> 
> so the 0 for LANTIQ is fine with the correct VPE payload. But for
> MALTA could cause major problems, if the VPE payload uses the top
> of memory for it's stack. So I would guess nobody uses this "mode".
> Therefore let's get rid of physical_memory in vpe.c completly.

Hi Thomas,

I had already concluded that MALTA's dtshim and physical_memsize
are independent so I should ignore those in any changes/patches.

I'll check into your suggestion to see what that looks like.

Thanks for the comments.
-- 
~Randy