[U-Boot-Users] MPC8540, UPM Writeburst generating also read bursts

Gerrit Van de Velde gerrit.vandevelde at gmail.com
Tue Jul 24 17:33:33 EST 2007

Hello again,

> Please don't top-post and please don't remove the list. (use reply-to-all)
> (and please move this thread over to linuxppc-embedded, as we are OT here)

Ok, I'll never do that again. And the topic has been moved.

> You don't have single read and write instructions in your UPM?
> Please post your UPM table.

I do have single reads and writes. The UPM is as follows (taken from
the upmtool output)

/* MxMR Configuration Code */
unsigned long MAMR = 0x40000;
unsigned long MBMR = 0x40000;
unsigned long MCMR = 0x40000;

/* UPM Table Configuration Code */
static unsigned long UPMATable[] =
	0x0faffc00,  0x0faffc00,  0x0fafdc04,  0x3fbffc01, //Words 0 to 3
	0xfffffc00,  0xfffffc00,  0xfffffc00,  0xfffffc00, //Words 4 to 7
	0x0ffffc00,  0x0ffffc00,  0x0ffffc0c,  0x0ffffc0c, //Words 8 to 11
	0x0ffffc0c,  0x0ffffc0c,  0x0ffffc0c,  0x0ffffc0c, //Words 12 to 15
	0x0ffffc0c,  0x0ffffc04,  0x3ffffc01,  0xfffffc00, //Words 16 to 19
	0xfffffc00,  0xfffffc00,  0xfffffc00,  0xfffffc00, //Words 20 to 23
	0x0fa3fc00,  0x0fa3fc00,  0x0fa3fc04,  0x3fb7fc01, //Words 24 to 27
	0xfffffc00,  0xfffffc00,  0xfffffc00,  0xfffffc00, //Words 28 to 31
	0x0ff3fc00,  0x0ff3fc00,  0x0ff3fc0c,  0x0ff3fc0c, //Words 32 to 35
	0x0ff3fc0c,  0x0ff3fc0c,  0x0ff3fc0c,  0x0ff3fc0c, //Words 36 to 39
	0x0ff3fc0c,  0x0ff3fc04,  0x3ff7fc00,  0xfffffc01, //Words 40 to 43
	0xfffffc00,  0xfffffc00,  0xfffffc00,  0xfffffc01, //Words 44 to 47
	0xfffffc00,  0xfffffc01,  0xfffffc00,  0xfffffc00, //Words 48 to 51
	0xfffffc00,  0xfffffc00,  0xfffffc00,  0xfffffc00, //Words 52 to 55
	0xfffffc00,  0xfffffc00,  0xfffffc00,  0xfffffc01, //Words 56 to 59
	0xfffffc00,  0xfffffc01,  0xfffffc00,  0xfffffc01  //Words 60 to 63

> Do you access the DDR memory aligned in 32byte cacheline sizes?
> The UPM propably cannot burst unaligned chunks properly.
> (I'm not sure about that, comments are welcome).
> 500MBit/s should be easy to handle with the UPM, if done right.

Yes target addresses are aligned to 32 byte words. I 'm not sure what
you mean with cachelines.

> 1) It makes sense to use the DMA to offload the CPU for copying bulk
> data if the CPU can be used for other stuff.

Ok, but currently our MPC8540 is a bit overkill, maybe later in the
life of our board it will be come necessary but at least not now.

> 2) Can you first make sure that your Gbit link is working fine by copying
> data from/to the CPU's memory without using the UPM?

That's something I should try first indeed, I'll update you/the list
if I know about the results

> I guess you will need to post more information about your
> system (schematics, code, UPM)...

I'll do that when UPM-less writes are much faster and you don't see
anything strange in the UPM table.

Gerrit Van de Velde

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