On Thursday 28 September 2006 5:55, Stefan wrote:
I seems to be overwritten in the meantime.
[Leonid] That what I was guessing... since when I get this register immediately after setting and print it out, register's value looks OK.
A look at the 440EP manual shows, that DCR reg 0x20 is the CPR0_CLKUPD register, which is most likely accessed each ms in the 440 timer interrupt (didn't check though).
[Leonid] This is not important for our subject, but I tried to work with DCR register 0xE (not 0x20!) which is System DCS address register SDR0_CFGADDR (not CPR0_CLKUPD) and offset 0x20 we see there corresponds to SDR0_SDSTP0 (Serial Device Strap Register 0). Anyway you most likely right - somebody access this Strap register frequently and set/get back to back combination is required to read the registers with indirect access via DCR.
What you really need, is an U-Boot command to set/get SDR registers, indirectly accessed via the DCR 0x0e/0x0f registers. Something like "setsdr/getsdr".
[Leonid] I thought rather of some generic function, allowing indirect access to DCR-related registers since 0xE/0xF is not only combination of address/data - for EBC they use 0x12/0x13 for instance. To that end, GET command must receive 3 "address" arguments - DCR address register, DCR data register and offset while SET will also need a value. Please advice on command's name. Something like that I guess:
getidcr e f 0x40 setidcr e f 40 0xbadd
where "i" in the middle stays for "indirect". What do you think?
Now regarding implementation. Simplest way is to call set_dcr()/get_dcr() from C code but that actually doesn't ensure that the register under consideration was not overwritten in between. I can disable interrupts, do you think it's OK? This is debug monitor function after all, nobody cares regarding performance here...
It would be best, if you could supply a proper patch with such additional commands.
[Leonid] It will be quite a honor for me to serve this community. Can you refer me to proper link how I do proceed with patch submission: review, help information, actual sources delivering, etc...
Thanks.
Best regards, Leonid.