Patches (was Re: Problem with L4Linux accessing ethernet clocks)

Adam Lackorzynski adam at os.inf.tu-dresden.de
Wed Nov 1 23:20:52 CET 2017


On Wed Nov 01, 2017 at 01:03:36 +0100, Paul Boddie wrote:
> On Wednesday 1. November 2017 00.38.23 Adam Lackorzynski wrote:
> > 
> 
> [Cache detail querying]
> 
> > I just modified the code to have a fixed value and that worked for me as
> > a quick hack. I don't think the value will ever change for a particular
> > CPU. But it's still a hack and there's a smarter way definitely.
> 
> In a lot of systems, I guess people would use a configuration setting for this 
> kind of thing (U-Boot seems to have a lot of this going on). I'd have to look 
> at the code to see how this instruction got included, though.

It's the MIPS-related cache handling in l4sys.

> > Debian is building pie code per default nowadays, I think that's where
> > it's coming from, and we should handle this.
> > 
> > The MIPS vendor compiler is actually gcc but an older one:
> > https://www.mips.com/develop/tools/codescape-mips-sdk/download-codescape-mi
> > ps-sdk-essentials/
> 
> I'm guessing that there might have been different defaults and therefore 
> corresponding assumptions that don't hold true for vanilla gcc.

Yes, that might actually be, but Debian/Ubuntu is pretty widespread so
it should work too.
 
> [Accessing 1GB]
> 
> > There's a hole, and it also looks like the first 256MB is mirrored at
> > 512MB. However, using all the memory is just a matter actually making it
> > known, I've just tried it and it seems to work. All Ci20's have 1GB,
> > right?
> 
> Yes. My interpretation was also that the first 256MB resides at zero for 
> compatibility with earlier SoCs in the family, and that they "started again" 
> at a higher location (at 512MB, I guess, if you've looked it up!) when their 
> products needed more address space.
> 
> Thanks for taking a look at this! I doubt that the CI20 is so high priority 
> now, but who knows what its corporate parents will do after their separation?

The Ci20 has a somewhat special CPU which needs some special treatment.
For that reason I was mentioning the Ci40 which is better in this
regard.



Adam



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