Re: [PATCH 0/4] Atari kernel-in-FastRAM patches, take three

From: schmitz <schmitz@biophys.uni-duesseldorf.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michael Schmitz <schmitz@mail.biophys.uni-duesseldorf.de>,
	Andreas Schwab <schwab@linux-m68k.org>,
	Michael Schmitz <schmitzmic@gmail.com>,
	Linux/m68k <linux-m68k@vger.kernel.org>,
	debian m68k <debian-68k@lists.debian.org>
Subject: Re: [PATCH 0/4] Atari kernel-in-FastRAM patches, take three
Date: Tue, 01 Apr 2014 20:45:36 +1300	[thread overview]
Message-ID: <533A6EA0.9030808@biophys.uni-duesseldorf.de> (raw)
In-Reply-To: <CAMuHMdUeMv1R69vSLv0HZpKEgVpRUG_iMs=61JWVubBsSN7VVA@mail.gmail.com>

Hi Geert,
>
>>>> do we know the size of the first memory chunk early enough in head.S?
>>>> Maybe it's time to increase INIT_MAPPED_SIZE at least in cases where
>>>> we know that there's more than 4 MB in the first memchunk ...
>>>>         
>>> How do you know?  You would have to reimplement the check paging_init
>>> does.
>>>       
>> I see - as a heuristic, we can probably assume that the first memchunk is
>> the relevant one, and especially in the case of FastRAM, also the larger
>> one.
>> Does this hold for Amiga/Mac/VME as well?
>>     
>
> People want to run the kernel in the fastest memory chunk, which is typically
> also the largest (slow Amiga mainboard memory may be 2 - 16 MiB for
> Linux-capable machines, accelerator memory may be larger).
>   

And the chunk the kernel runs from would always be the first chunk 
listed in bootinfo, since that's the one mapped at virtual address zero?

> Don't know about Mac, but I have some memories of interleaved banks
> and such...
>   

Not sure I've ever seen accelerators or memory upgrades on the Macs that 
I hacked on. 4 MB was sort of plenty in those days.

Cheers,

    Michael