Hello,

On Thu, 21 Mar 2013 09:54:46 +0100
CF Studelec [off-list ref] wrote:

Hello,

This is a simple board base on mpc5121e MCU.


Gpio is detected: kernel is compiled with its support - i got
gpiochip_find_base: found new base @224 in dmesg - on kernel 3.0.4.

 
But i'm unable to access it through /sys/class/gpio. I can successfully
export a pin (ie, if i type cat 224 > export, gpio224 is created), but i
can't successfully control it:

 

echo "out" > /sys/class/gpio/gpio224/direction

cat /sys/class/gpio/gpio224/value

0

echo 1 > /sys/class/gpio/gpio224/value

cat /sys/class/gpio/gpio224/value

0

My need is a simple chipselect (well, 3 chipselect exactly ), for a
custom design. Running linux is mandatory. I suspect the MPC5121e to be
in the bad function mode, so:

- does anyone knows how to change mode ? What register can i acces and
how ? does it worths a try ?

For GPIO0 - GPIO7 pins you additionally need to configure the pin mux
for GPIO mode, see IO_CONTROL_GP register description in the manual.

- does anyone successfully performed simple IO control ?

We use it all the time, i.e. as SD-Card detect and/or
write-protect GPIOs, as SPI Chips-Select GPIOs, etc. It works.

Last thing, i have tryed to access internal registers through /dev/mem,
but no success. There are very few ressources available for this
microcontroler, but i'm stick to it. Perhaps anybody knows how to access
(read) internal registers with /proc or sys-fs ?

Accessing registers using /dev/mem should work (tested using
devmem2.c tool with recent v3.9-rc4 kernel. Should work with
older kernels too).

Alternatively (as a quick test) you could configure the registers
under U-Boot using "mw" command, assuming you are using U-Boot as
a bootloader.

HTH,

Anatolij

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