[U-Boot-Users] Q about automatic dram size detection in sdram_init()

[U-Boot-Users] Q about automatic dram size detection in sdram_init()

["SYLee"]

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[U-Boot-Users] Q about automatic dram size detection in sdram_init()

[Stefan Roese]

SYLee!

The code works fine on all different memory configutations. This is
because of the mirroring of the written values. For example on a system
with 64MByte SDRAM a write to "ADDR_64MB" will mirror to one of the
smaller addresses and the current test will fail! So this is perfectly
OK.

Best regards,
Stefan Roese

-----Original Message-----
From: u-boot-users-admin@lists.sourceforge.net [mailto:u-boot-users-
admin at lists.sourceforge.net] On Behalf Of SYLee
Sent: Thursday, July 15, 2004 3:00 AM
To: u-boot-users at lists.sourceforge.net
Subject: [U-Boot-Users] Q about automatic dram size detection in
sdram_init()


Hi, 

In cpu/ppc4xx/sdram.c, in sdram_init(), the following seems to be
wrong. 

/* 
* Test if 128 MByte are equipped (mirror test) 
*/ 
*(volatile ulong *)ADDR_ZERO = MAGIC0; 
*(volatile ulong *)ADDR_08MB = MAGIC1; 
*(volatile ulong *)ADDR_16MB = MAGIC2; 
*(volatile ulong *)ADDR_32MB = MAGIC3; 
*(volatile ulong *)ADDR_64MB = MAGIC4; 

if ((*(volatile ulong *)ADDR_ZERO == MAGIC0) && 
    (*(volatile ulong *)ADDR_08MB == MAGIC1) && 
    (*(volatile ulong *)ADDR_16MB == MAGIC2) && 
    (*(volatile ulong *)ADDR_32MB == MAGIC3)) { 
/* 
* OK, 128MB detected -> all done 
*/ 
return; 
} 

I think the following conditional expression must be inserted at if
statement: 
(*(volatile ulong *)ADDR_64MB == MAGIC4) 

The above case is also applied to 64MB and 32MB detection. 

Thanks. 
SYLee. 


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[U-Boot-Users] Q about automatic dram size detection in sdram_init()

[Wolfgang Denk]

In message <20040715100012.40f5d71c00027b490053c837.188@empal.com> you wrote:
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[U-Boot-Users] Q about automatic dram size detection in sdram_init()

[Wolfgang Denk]

In message <001501c46a3d$9705b720$0212000a@PCSTEFAN> you wrote:
> 
> The code works fine on all different memory configutations. This is
> because of the mirroring of the written values. For example on a system
> with 64MByte SDRAM a write to "ADDR_64MB" will mirror to one of the
> smaller addresses and the current test will fail! So this is perfectly
> OK.

If you have a 64MB system, I'd  expect  that  a  write  to  ADDR_64MB
succeeds?

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
Quantum Mechanics is God's version of "Trust me."

[U-Boot-Users] Q about automatic dram size detection in sdram_init()

[Stefan Roese]

Wolfgang!

> > The code works fine on all different memory configutations. This is
> > because of the mirroring of the written values. For example 
> on a system
> > with 64MByte SDRAM a write to "ADDR_64MB" will mirror to one of the
> > smaller addresses and the current test will fail! So this 
> is perfectly
> > OK.
> 
> If you have a 64MB system, I'd  expect  that  a  write  to  ADDR_64MB
> succeeds?

The memory controller is previously setup to 128MB. So a write to 64MB
is OK, and _will_ be mirrored to a lower address on a 64MB system!

I agree that the code is pretty ugly and I am thinking about reworking
it.

Best regards,
Stefan Roese