[Letux-kernel] [OpenOCD-devel] [PATCH]: d86217d board: add Skytone Alpha 400

[Paul Boddie]

[Dropped OpenOCD list since they just bounce my messages]

On Tuesday, 17 November 2020 23:12:50 CET Lubomir Rintel wrote:
>
> Yes. My machine (that's an Elonex Onet+ I think) actually had a connector
> (a 4-pin molex picoblade or something similar), accessible from the battery
> compartment soldered from factory, though not the JTAG one.
> 
> In any case, I've got a setup with both UART and the JTAG hooked on at
> this point. I intend to get the thing booting as time permits. In the
> other message I shot your way today [1] I shared what the situation
> looks like at this point.
> 
> [1]
> https://lists.goldelico.com/pipermail/letux-kernel/2020-November/005856.html

Thanks for all the hard work. Having a UART connector available as standard 
must be very helpful.

On the topic of booting, I just updated the Letux 400 hardware documentation 
with a minimal edit with regard to the operating system timer (OST) registers:

https://projects.goldelico.com/p/letux400/page/Clocks/

These are arranged differently on the JZ4730, and while I might have tried to 
make sure they are somehow handled in the clock driver part of the Linux 
kernel (drivers/clk/ingenic/tcu.c), it is possible that I overlooked 
something.

As you may have seen with my patches, I removed the dedicated OST 
(TCU_CLK_OST) and provided three timers that are actually provided by the 
JZ4730's OST peripheral which happens to reside in the same address region as 
the JZ4740's TCU peripheral. My patches just make these JZ4730 registers 
appear as if they were provided by the TCU (include/linux/mfd/ingenic-tcu.h), 
and the distinction is probably irrelevant for our purposes, anyway.

But what I may not have checked is whether the context switching code actually 
uses the appropriate timer. If it expects TCU_CLK_OST to be around, this is 
likely not to work. Instead, it should use one of the TCU_CLK_TIMERs.

I hope this makes sense. It is rather late in the evening for me now.

Paul