Thread (2 messages) flat view 2 messages, 2 authors, 2009-07-02

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
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