From mboxrd@z Thu Jan  1 00:00:00 1970
From: Scott Wood <scottwood@freescale.com>
Date: Thu, 27 May 2010 15:05:36 -0500
Subject: [U-Boot] [PATCH] powerpc: add support for the Freescale P1022DS
 reference board
In-Reply-To: <20100527195318.71B5EEAC238@gemini.denx.de>
References: <1274392909-16422-1-git-send-email-timur@freescale.com>
	<20100520223324.50594CCF026@gemini.denx.de>
	<4BFC1736.5030902@freescale.com>
	<20100526201014.97886EAC238@gemini.denx.de>
	<4BFD837D.2040508@freescale.com>
	<20100527070235.E8812EAC238@gemini.denx.de>
	<4BFE823A.1080409@freescale.com>
	<20100527181118.3C9F7EAC238@gemini.denx.de>
	<4BFEB922.9040106@freescale.com>
	<20100527190340.GA5915@schlenkerla.am.freescale.net>
	<20100527195318.71B5EEAC238@gemini.denx.de>
Message-ID: <4BFED090.1040305@freescale.com>
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On 05/27/2010 02:53 PM, Wolfgang Denk wrote:
> Dear Scott Wood,
>
> In message<20100527190340.GA5915@schlenkerla.am.freescale.net>  you wrote:
>>
>> Passing the actual, known size of RAM (why guess when we know?) as "maxsize"
>> should eliminate the machine check problem[1] -- you'd just be using it as a
>> not particularly exhaustive memory tester.  I don't see why it should be
>> mandatory.
>
> Typically we chose  "maxsize" to b twice the actual possible maximum
> to allow for real testing.

If you set maxsize beyond what you expect to find, how are you going to 
constrain it to operating on one bank?

>> It also doesn't handle non-power-of-two sized memory -- don't rely on the
>> value it returns.
>
> Such configurations are usually set up of from several differently
> sized banks of memory, and get_ram_size() is always run per bank. So
> as long as chip manufacturers continue to make RAM chips with
> power-of-two sizes only, everything should be fine.

So it's not the board code at all that should be calling this, it's the 
SDRAM code?  Which is already in u-boot, and not in this patch (other 
than some board-specific tweaks)?

>> [1] It's worse than machine checks, what if some I/O device is mapped
>> directly after RAM?  IIRC people have run into this sort of problem doing
>> this type of memory sizing on PCs.
>
> Well, let's call this a bug in setting up the memory map for the
> system ;-)

Let's not.  It can be crowded enough as is, we don't need more 
restrictions coming from u-boot wanting to do questionable and 
unnecessary things.

-Scott