[U-Boot-Users] 83xx SPD_EEPROM DDR2 Issues

[Russell McGuire]

Bruce,

I think you've hit upon something here.
After checking the SPD tables during the intial comparison for data rates,
it is clear that 1) the DDR2 bit fields are not defined properly. i.e. it
looks like the big if-if-else statement specifically does not have valid
DDR2 values defined for clk_cycle2 (30h, 3Dh, 50h) not DDR1, so we're going
need an extra 3 defined at a minimum. 

I haven't gone through the rest yet, but most likely if we want to keep SPD
working for DDR2, we'll have to add the DDR2 definitions SPD into the code,
as it looks like the DDR2 port is only partially complete.

-Russ

-----Original Message-----
From: Bruce_Leonard at selinc.com [mailto:Bruce_Leonard at selinc.com] 
Sent: Tuesday, June 03, 2008 3:31 PM
To: rmcguire at videopresence.com
Cc: 'Maggs Bill'; 'Steve Hensley'; u-boot-users at lists.sourceforge.net;
u-boot-users-bounces at lists.sourceforge.net
Subject: Re: [U-Boot-Users] 83xx SPD_EEPROM DDR2 Issues

> 
> Today, I went to my local PC store, and bought EVERY type of DDR2 
> SODIMM memory they had, Kingston, Crucial, PC4200, PC5300 four 
> different kinds of memory, and NONE of them will boot with U-boot now.
> 

Hay Russell,

I don't have patches, and I haven't worked on this in a long time because 
we have a single build option for our RAM.  However, I may have a pointer 
for you to look at if you haven't already.  Way back when we we're 
thinking about having SPD support I did spend some time digging through 
spd_sdram.c and found that some of the calculations were....I won't say 
broken, but not exactly acurate because of they way they were done.  I 
also found that the highest data rate speeds supported didn't go high 
enough to support all of the speeds DDR2 can have.  Like I said, it's been 
a long time and someone may have already fixed it, but it had to do with 
calculating max_data_rate, effective_data_rate, and caslat in spd_sdram(). 
 It was something I ment to fix and then never did because we didn't end 
up using it.  Hope this helps.  If not, sorry for the noise.

Bruce