AW: How to set DDR data bus width to 16Bit
From: Frank Prepelica <hidden>
Date: 2009-07-02 09:45:08
you have to do it via your bootloader (u-boot) which sets up the DDR memory controller. Linux (already) assumes memory is available. Are you sure linux kernel is changing DDR_SDRAM_CFG ? When our linux-2.6.28 kernel is up, it's still 0xc3080000 when I read physical address 0xe0002110.
Hi Norbert, thank you for your fast reply! You are absolutly right! I made a silly mistake. I've read the value of the 0xe0002110 with a 8bit pointer. The value is actually 0xC3100000 which means the 16bit bus width is set. Just to be sure. Is this the only change (in the bootloader) I have to make that all data accesses are 16bit wide?
Btw. We did some performance tests with 16 bit bus-width (DDR2 memory) and surprisingly performance was almost as good as 32 bit bus-width
This is exactly our intention to test. Thanks for that hint. Very good to know! Thank you. Best regards Frank