Re: [uCsimm] ucsimm-head.S broken?

From: Vladimir A. Gurevich (vgurevic@cisco.com)
Date: Wed Jan 19 2000 - 01:26:19 EST


Hello Tom,

Tom Walsh wrote:

> It seems to be a bit strange, while I was bringing up the board and
> getting my flashloader built I had the '*.b' file programmmed to dump 0x0038
> into 0xfffff902 to get 9600 baud, oh well, there has been much going on here
> in the last 5 days, I could be mistaken.

You can actually see the process if you look at my bbug script.
Initially, when you power up the board the baud rate is set to be 9600.

Then bbug does the following:

1) It clears PRESC bit in PLLCR thus immediately changing the baud rate
   from 9600 to 19200.

2) It sets the high byte in UBAUD to be zero thus setting speed to 38400
    (in fact UBAUD changes from 0x0126 to 0x0026)

3) It sets the low byte in UBAUD to 0x38 and this finally gives 115200,
   since UBAUD becomes 0x0038

> I still am working my way through that file, why is the 1 meg flash
> memory mapped to 0x10c00000? Why isn't it mapped to 0x10000000 even? This is
> causing me problems in mapping my memory <sigh>.

I think this is PalmPilot "heritage". On all my boards I map it to
0x10000000. But it should not matter. What really matters is that your
*-head.S file should program chip selects in such a way that the actual
mapping corresponds to what is in your .ld file. In fact, when I just
started to play with uClinux I used the original Motorol mapping on
M68EZ328ADS and it worked without any problems. 68EZ328 is pretty
flexible in this respect.
 
> I got my board to emit the 'ABCDEF' and the ucsimm copyright, then it buss
> faults: the address lines stop "wiggling", so I am going after the ld file
> mapping, tomorrow.

Yes, you probably tweaked the stuff too much. Since I've already brought up
uClinux on 4 different boards I can tell you that the required changes are
very minimal.

> You use the /linux/arch/m68knommu/platforms/68EZ328/ads_flash.ld for the
> Mot eval board?

Yes. And alma_ans_flash.ld for another custom board which also has cs8900
on it.

> Maybe I'd be better off using the kernel that you have (actually the ld
> file + sources) as I wish to have the entire o/s running in DRAM and leave
> the Flash for a database store / update.

You'd better switch to 2.0.38.1pre1 it has the framework for that. In fact
all my ports can be compiled to run either from FLASH or from DRAM. And it
has lots of other fixes and good stuff too.

You can grab ftp://ftp.employees.org/linux-2.0.38.1pre1-vag.tar.gz
which contains my ports to 3 different boards (ads, alma_ans and etherphone).
I think you'll be able to deduce a lot of info if you compare them.

And, of course, don't hesiate to ask me.

Happy hacking,
Vladimir

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