[U-Boot] [PATCH 2/2] edb93xx sdram: fix initialization

[Matthias Kaehlcke <matthias@kaehlcke.net>]

Hi Alessandro,

El Thu, Feb 11, 2010 at 09:46:50PM +0100 Alessandro Rubini ha dit:

> The configuration of SDRAM needs two more writel() operations,
> otherwise some boards won't be able to boot. These additional writes
> are present in vendor assembly code but were forgotten during the
> rewriting in C.
> 
> Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
> Acked-by: Matthias Kaehlcke <matthias@kaehlcke.net>

i gave my ack after a visual review of the patch, without having
tested it. i just installed a patched u-boot on one of my boards and
it doesn't boot :(

at a first glance the offender seems to be the write to the GlConfig
register in force_precharge(), after commenting this line the board
comes up.

comparing with the initial SDRAM initialization written in
assembly i noticed that you set the INIT bit in force_precharge(),
while the assembly code doesn't. according to the user manual the INIT
must be set to issue PRECHARGE ALL, but if i don't get it wrong
this isn't our case, as we assume that PRECHARGE ALL doesn't work (see
errata), thus we precharge manually by reading from the RAM.

but even after clearing the INIT bit my board refuses to boot. i hope
i'll find time this weekend to track this down. if you want to have a
look at the initial sequence in assembly, it can be found here:

http://lists.denx.de/pipermail/u-boot/2009-December/065133.html

cu

-- 
Matthias Kaehlcke
Embedded Linux Developer
Barcelona

          We can't solve problems by using the same kind
             of thinking we used when we created them
                         (Albert Einstein)
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