[U-Boot-Users] Query related to POST of SDRAM
Hi All, In file post/memeory.c the following comment is there /* * This is 64 bit wide test patterns. Note that they reside in ROM * (which presumably works) and the tests write them to RAM which may * not work. * * The "otherpattern" is written to drive the data bus to values other * than the test pattern. This is for detecting floating bus lines. * */ This comment gives an hint that this code is specifically for the 64 bit wide SDRAM only. I ran the same code on the ep8248 board in which the port size of the RAM is 32 bits it worked there, didn't throw any error. I just want to make it sure that, if the port size of the RAM is 32 bits will this test work with out any modifications or do I have to make some changes.
Regards, Vikrant
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Vikrant_Basotra wrote:
Hi All, In file post/memeory.c the following comment is there /*
- This is 64 bit wide test patterns. Note that they reside in ROM
- (which presumably works) and the tests write them to RAM which may
- not work.
- The "otherpattern" is written to drive the data bus to values other
- than the test pattern. This is for detecting floating bus lines.
*/ This comment gives an hint that this code is specifically for the 64 bit wide SDRAM only. I ran the same code on the ep8248 board in which the port size of the RAM is 32 bits it worked there, didn't throw any error. I just want to make it sure that, if the port size of the RAM is 32 bits will this test work with out any modifications or do I have to make some changes.
Regards, Vikrant
Confirmed: the processor in hardware does the size translation between the register load/store size (64 bits) and the memory bus (could be 8/16/32/64 bits in various processors and configurations) by doing multiple bus cycles as necessary.
The intent of using 64 bit transactions is to stress the bus and use all of the bus bits when running a 64 bit wide bus.
gvb
In message 3D9FDCA910DD4445896A0BE5ECF009D45098F1@bla.satyam.com you wrote:
In file post/memeory.c the following comment is there
There is no such file in the U-Boot code :-)
This comment gives an hint that this code is specifically for the 64 bit wide SDRAM only.
No. This is NOT the right conclusion. Please read here:
This is helpful for testing memory on processors which have a 64 bit wide data bus.
I just want to make it sure that, if the port size of the RAM is 32 bits will this test work with out any modifications or do I have to make some changes.
The test works on 32 wide busses, too.
Best regards,
Wolfgang Denk
participants (3)
-
Jerry Van Baren -
Vikrant_Basotra -
Wolfgang Denk