[Letux-kernel] jz4730-i2c - clocksource

[H. Nikolaus Schaller]

> Am 02.04.2021 um 18:50 schrieb Paul Boddie <paul at boddie.org.uk>:
> 
> Nikolaus,
> 
> Going back almost a month here, but I recently saw this message:
> 
> "Unhandled EFAULT with letux kernels built with newer gcc compilers"
> 
> https://groups.google.com/g/mips-creator-ci20-dev/c/SqjtFOXT62Y

Looks as if I no longer receive messages from the mips-creator list :(

Will have to check why. Maybe Google did throw me out once again.

> Now, the problem is related to futex_detect_cmpxchg, which sounds as if it is 
> the method by which the kernel detects whether it can use the appropriate 
> load-link/store-conditional instruction. And this reminded me of the 
> following:
> 
> On Saturday, 6 March 2021 18:07:58 CEST H. Nikolaus Schaller wrote:
>> Hi Paul,
>> 
>>> Am 06.03.2021 um 16:55 schrieb Paul Boddie <paul at boddie.org.uk>:
>>> 
>>> A brief look at arch/mips/include/asm/futex.h indicates that the LL/SC
>>> (https://en.wikipedia.org/wiki/Load-link/store-conditional) instruction is
>>> required for futex support. I am not sure this is provided on the JZ4730
>>> or
>>> even on other early XBurst1 CPUs.
>> 
>> Oh, interesting! Maybe we have hit some fundamental issue here.
> 
> It seems like others have encountered what they believe is a compiler bug, but 
> I seem to remember that you still use GCC 4.9 or something fairly old. But I 
> thought it might be useful to hear about this.

Yes, I still use my 4.9 toolchaian.

But I am still in the middle of updating my cross toochains (which also must
include Objective-C)...

What I want to have is a compatible toolchain for every (available) combination of

	Squeeze, Jessie, Stretch, Bullseye, Buster

with

	arm64, armel, armhf, i386, mipsel, riscv

And each one breaks my scripts at a different detail... And fixing one may
affect another one unless I add too detailled special cases.

But this will include newer gcc for Stretch, Bullseye etc. so that I
can start hunting for compiler bugs.

> 
> Also, there was a message about the CI20 only using 256MB of RAM with one of 
> your kernels:
> 
> https://groups.google.com/g/mips-creator-ci20-dev/c/gNsIXU7cg6g

Ok, I haven't checked memory size with the CI20 recently but should do :)

> 
> I don't remember if you saw this already.

No, not yet...

BR and thanks for the hints,
Nikolaus

PS: I still haven't sound working but have started to analyse hardware.
It can report a headset plugin so we should add some detection.
And the speakers need a separate enable GPIO. Finally, there is a built-in
microphone so that in theory the machine could be Skype capable when adding
an USB webcam... Well, AFAIK there is no Skype binary for Debian/MIPS. And
processor speed is very likely not sufficient.