[U-Boot-Users] SDRAM on ixp425

[Jonathan Pratt]

Hi all.

This isn't really a question about uboot, more about the ixp425

We have an ixp425 product with a footprint for 2 SDRAM components. When
we use 2 x IS42S16800 (8M x 16 x 4 banks) for a total of 32MByte
everything works fine. But replacing these components with 2 x
IS42S16400 (4M x 16 x 4 banks) for a total of 16MByte the board won't
boot.

In both cases the PHYS_SDRAM_1_SIZE is set to 0x01000000 (16MByte) since
the intent was always to use the smaller SDRAM configuration.

The SDRAM settings for the 32MB version are:
#define CFG_SDR_CONFIG				0x18
#define CFG_SDR_MODE_CONFIG			0x01
#define CFG_SDRAM_REFRESH_CNT			0x400

And for the 16MB version:
#define CFG_SDR_CONFIG				0x3A
#define CFG_SDR_MODE_CONFIG			0x01
#define CFG_SDRAM_REFRESH_CNT			0x400

[ie the only change between the two configurations is the SDR_CONFIG
value]

In particular the 64M enable (in SDR_CONFIG) is set for the 64MBit parts
and the mem config field is set to %010 which is what the data sheet
prescribes for two 4M x 16 parts.

The first version works fine (using 8Mx16x4 parts). The second version
fails to boot with the appropriate components (-7 {143MHz} speed grade).

Has anyone used 64Mbit components with the ixp425 or similar? Can anyone
comment on why the second configuration would fail? 

Thanks

Jonathan Pratt
ELPRO Technologies Pty Ltd