Adding hardware access to L4Linux, and killing serial console

Peter Howard pjh at
Fri Jun 6 02:16:46 CEST 2014

Dear all,

I'm currently trying to add extra hardware access to L4Linux on the
da850.  I'm having reasonable success (thanks Taueng!), but have hit a
problem with interrupts.  I have enabled:
      * GPIO access (working, with problem described below),
      * DMA access (working, I think), 
      * Clock access (working, insomuch as the GPIO and DMA stop giving
        clock errors),
      * MMC/SD access (not working - and until it does I'm not 100% sure
        about DMA).

(For anyone who knows the omapl138, the mux setup _is_ being handled;
part of the bsp code in Fiasco).

I hit my current problem when I got the Clock access working, and the
GPIO driver started registering interrupts.  At that point the serial
console stops responding.  It prints, but any attempts to type anything
fail.  Simply commenting out the second half of davinci_gpio_irq_setup()
removes the problem.  Of course then gpio interrupts can't work (not
that I know if they are working yet).  So clearly registering those
interrupts is affecting the serial console being notified of data

I don't expect anyone here to have the answer.  But to work out the
problem I need to better understand how the virtual serial works in
L4Linux.  So can anyone give me/point me to a description of how it does
work, along with the relevant driver code?


Peter Howard <pjh at>

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