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RE: dynamic memory detection


This type of thing is highly dependent on the SDRAM controller and
knowing the CPU address decoding of the controller (which bits of the
CPU's physical addresses become COL/ROW/Bnk bits).  Then by configuring
the controller such that you can detect address wraparound by writing to
address boundaries to figure out the geometry of that bank.

>-----Original Message-----
>From: ecos-devel-owner@sources.redhat.com [mailto:ecos-devel-
>owner@sources.redhat.com] On Behalf Of alfred hitch
>Sent: Wednesday, May 11, 2005 3:38 AM
>To: Robin Randhawa
>Cc: ecos-devel@ecos.sourceware.org
>Subject: Re: dynamic memory detection
>
>Hi Robin,
>
>thanks for your reply,
>
>but could u please give more details on ur SDRAM sizing algo ?
>how were u doing that ?
>
>then I will see if I can do the same on IXDP or not ..
>My fear is that I cannot as I was discussing with someone who has
>worked extensively on x86 plattforms.
>In there on northbridge there is a device generally which can be read
>to find the size etc of dram ,
>
>as of now I dont see any such stuff on ixp data sheet.
>
>May be this is the reason that redboot etc dont have this as it might
>not be a portable feature, but come to think of it, on boards where
>one can, it should be implemented ?
>
>can u tell how u did the sdram sizing thing ? I can infact choose
>u-boot also as my bootloader that isnt the issue presently.
>
>Alfred
>
>On 5/10/05, Robin Randhawa <robin.randhawa@gmail.com> wrote:
>> Hi.
>>
>> While I do not have any hands on experience with the IXDP425, your
post
>> reminded me of some work I had done for another board (one based on
the
>> AMD Elan SC520 micro) to which I was porting the u-boot bootloader. I
>> used SDRAM sizing algorithms to determine stuff like :
>>
>> 1. The number of external SDRAM banks
>> 2. The bank geometry
>> 3. Column widths etc.
>>
>> The net result was that the total amount of SDRAM was detectable at
>> runtime.
>>
>> I do not have any devel experience with redboot, but being a
bootloader
>> of certain pedigree (its always been a great help), I wonder why
SDRAM
>> sizing and detection is not an option myself.
>>
>> A bootloader would be expected to configure a board in preparation
for
>> either an OS to take over safely or a standalone application. Either
>> ways, memory detection would be an added advantage and would not be
too
>> costly in terms of the added footprint, which incidentally, would be
one
>> of the concerns. The only issue could be the need for
per-architecture,
>> per-processor support since SDRAM detection is quite a specific
>> technique, but eCos' beautifully modular design should easily allow
>> that.
>>
>> Maybe the maintainers/developers would like to opine on this ?
>>
>> Cheers,
>> Robin
>>
>> On Tue, 2005-05-10 at 03:36 -0400, alfred hitch wrote:
>> > Hi All,
>> >
>> > I am working on a IXDP425 based plattform,
>> >
>> > If I understand it correctly there is no bios on it, and so for
>> > physical memory on the system, redboot has to depend on constant /
>> > #defines at compile time.
>> >
>> > What if one wants to dynamically detect these ?
>> > Why cannot we read the memory registers, while we are in redboot
and
>> > set up things accordingly ??
>> >
>> > ( I remember doing something similar while playing around in
netbsd,
>> > from smbus via open i/o ports it used to read the memory rows,
>> > coloumns etc and find out the size)
>> >
>> > I am sure there is some glitch in doing this, and I am missing
>> > something basic here,
>> > can someone please correct me here.
>> >
>> > Cheers,
>> > Alfred
>> >
>>
>>


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