[Gta04-owner] ANN: hw-validation kernel got high-speed (up to 3 MBit/s) UART driver (omap-serial.c)
Dr. H. Nikolaus Schaller
hns at goldelico.com
Sun Dec 18 21:35:39 CET 2011
After two days of deeply digging into the guts of the Linux
sources, I have backported the omap-uart driver
(omap_serial.c) that was introduced in Linux 2.6.36 or so
to our 2.6.32 based hw-validation kernel.
The reason to do this is that we now can test and
switch the Bluetooth interface to 3 MBit/s during
board production test which allows to check the
Bluetooth 2.0 EDR speed of the chip.
There is one minor stumbling block: the new UART
driver is not registered as /dev/ttyS0 to /dev/ttyS2 but
/dev/ttyO0 to /dev/ttyO2.
This means that the bootargs in U-Boot must
be changed or you will not see the boot log on the
RS232. If you don't change, you will see it scrolling
rapidly off the LCD (and it may interfere with X11).
Next, /etc/inittab may also need to be fixed so
that you can login through RS232 (the prebuilt
Debian/LXDE image on the goldelico server
is already prepared for that).
Finally, the user space tools and programs that
rely on /dev/ttyS0 and /dev/ttyS1 (mainly reading
the GPS chip and Bluetooth) need to be
Please also note that although these /dev/ttyS device
files still exist, they return I/O errors only.
The documentation has already been updated
to reflect the new file names:
To install this kernel, fetch the new debian package (kernel-image-gta04):
(please also update the U-Boot package since
it automagically fixes the boot.scr).
Finally, the source code commits can be found here
(although not important for the 3.x kernel development):
A final note: The RS232 interface (ttyO2) may
not be reliable at speeds > 115200 bit/s at
low temperature. This has its root cause in
some CMOS transistors introducing too much
propagation delay at low temperatures.
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