[Letux-kernel] [Tinkerphones] CI20 - was Re: New LetuxOS Kernels and some tricks and thoughts

[H. Nikolaus Schaller]

Hi Paul,

> Am 12.06.2019 um 18:37 schrieb Paul Boddie <paul at boddie.org.uk>:
> 
> On Tuesday 11. June 2019 17.38.20 H. Nikolaus Schaller wrote:
>> Hi Paul,
>> also adding the letux kernel mailing list because discussion becomes quite
>> kernel focussed...
> 
> OK, maybe my message will bounce, though, because I am not subscribed to that 
> list.

Seems to have worked :)

http://lists.goldelico.com/pipermail/letux-kernel/2019-June/003594.html

> 
> [...]
> 
>> I have just booted sucessfully the letux-5.2-rc4 kernel. Log is attached.
>> It seems to ignore NAND completely.
> 
> Yes, support for the specific kind of NAND on the CI20 was dropped in the 
> mainline kernel because it is the "wrong" type, or something. There was 
> argument about it being unreliable and no-one being able to know when it 
> fails, or something like that, so the kernel developers just pushed it over 
> the side. Obviously, this came as a surprise to anyone thinking they could 
> upgrade their kernel and expect everything to keep working.

Yes, that is sad, but not the most important issue. It may be even better
to have the NAND as a fallback boot option if the SD card becomes broken.

> Anyway, I tried booting the 5.1.8 kernel (from upstream) attached to the 
> serial cable and it did actually boot in the end. I don't get any logging to 
> UART0 despite changing the device tree file and doing "make uImage" but maybe 
> that isn't sufficient. Also, I couldn't figure out how to make systemd start a 
> terminal over UART0 (/dev/tty0), which was easily done using /etc/inittab 
> before some people decided they knew better about how things should be set up.
> 
> So, I ended up investigating using the UART4 connector which is unreliable 
> mechanically for those of us using female header connectors.

I have looked around for a pre-crimped 4-pin JST-XH socket with cable ends and
did find one as "3s battery balancer cable". There are other offers of course.

It is also easy to find JST-XH sets with the plastic parts and the connector
pins, but it needs a special crimping tool to build a cable that can't easily
be pulled out.

And I soldered the 3 significant wires to a normal 6-pin 2.54mm header which I
can directly connect to a FTDI adaper.

> 
>> The only problem seems to be "spidev at 0 enforce active low on chipselect
>> handle" which indicates a missing DT property.
>> 
>> What I wonder is where the LEDs (LED0 .. LED3) near the Ethernet controller
>> chip DM9000C are connected to... I could not locate them in the
>> schematics...
> 
> Aren't they the MMC indicators?

I have never seen them being active...

> 
>> It mentions only the RED/BLUE D5 and two wires LED1 and LED2 going from
>> DM9000C to the RJ45 socket which has the two Ethernet status LEDs.
>> 
>> It is likely that they go to some SD8..SD15 of the DM9000C but it seems that
>> the schematics do not exactly match my (pink CI20 V2a) board. But I also
>> could not locate an LED or GPIO controller driver for the DM9000C... So
>> there is no easy way to get them blinking (heartbeat, cpu, mmc activity).
> 
> So it seems that the LEDs are a general problem given that they do not 
> indicate MMC activity and made me think that the board hadn't booted.

Therefore it would be nice if we could make them work and set the default-triggers
in device tree to CPU activity, heartbeat and MMC activity.

> Since I  don't have the board connected with a serial cable and Ethernet at the same 
> time, I don't know whether the networking actually works, but ifconfig does 
> seem to show eth0 set up, albeit without an address.
> 
> Maybe I will try and let the board boot on the network again and just wait for 
> it to appear or not appear.

I have neither observed reboot problems nor Ethernet not working.

Maybe the DHCP isn't working reliable on your setup. Or the Ethernet gets a
random MAC address so that the IP address changes after every reboot. Do the
LEDs built into the Ethernet socket blink and show activity?

BR,
Nikolaus