[U-Boot-Users] Query related to POST of SDRAM

[U-Boot-Users] Query related to POST of SDRAM

[Vikrant_Basotra]

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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[U-Boot-Users] Query related to POST of SDRAM

[Jerry Van Baren]

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

[U-Boot-Users] Query related to POST of SDRAM

[Wolfgang Denk]

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

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"The net result is a system that is not only binary  compatible  with
4.3  BSD, but is even bug for bug compatible in almost all features."
- Avadit  Tevanian,  Jr.,  "Architecture-Independent  Virtual  Memory
Management  for  Parallel  and  Distributed  Environments:  The  Mach
Approach"