GPIO not working with RT patch

fvllml

I'm trying to use GPIO pins on up2.

My kernel is

Linux up 5.4.65-rt38+ #1 SMP PREEMPT_RT Mon Feb 28 13:42:31 CET 2022 x86_64 x86_64 x86_64 GNU/Linux

I compiled this up linux repository with the RT patch for the right kernel version and the following options:

  SYSTEM_REVOCATION_KEYS: no
  SYSTEM_TRUSTED_KEYS: no

  HZ_PERIODIC: yes
  NO_HZ_IDLE: no
  CONFIG_NTP_PPS: no
  HIGH_RES_TIMERS: yes
  CONFIG_HZ_1000: yes
  CONFIG_HZ: 1000
  CONFIG_OF: no
  CONFIG_AUFS_FS: no

  CONFIG_PREEMPT_RT: yes
  PREEMPT: yes
  PREEMPT_RT_FULL: yes
  PREEMPT_COUNT: yes
  PREEMPTION: yes
  DEBUG_PREEMPT: yes 

  CPU_IDLE: no
  INTEL_IDLE: no
  CPU_FREQ_DEFAULT_GOV_PERFORMANCE: yes

Then I installed the upboard-extras package

# Install extras
sudo add-apt-repository ppa:aaeon-cm/5.4-upboard
sudo apt update
sudo apt install upboard-extras

# Add groups
for group in gpio leds spi i2c; do
    if ! getent group $group >/dev/null; then
        addgroup --system $group
    fi
done

# Add User
sudo usermod -a -G gpio ${USER}
sudo usermod -a -G leds ${USER}
sudo usermod -a -G spi ${USER}
sudo usermod -a -G i2c ${USER}
sudo usermod -a -G dialout ${USER}

sudo reboot

I am able to communicate with a chip using spi so I think the permissions are right.

I tried the following code without success

echo 432 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio432/direction
echo 1 > /sys/class/gpio/gpio432/value

I measure with a multimeter on pin 432 (pin 13 from this wiki and I get 0.1V.

Am I missing something?
PS: I cannot see anything when ls /sys/class/leds/, why?

fvllml

My problem was that I was compiling the kernel with a generic ubuntu configuration and not the up-board configuration.

I instealled Ubuntu 20 again, then used the procedure in the wiki to patch the kernel with the up-board kernel. Then I copied back the config at /boot/ and used it to compile the kernel again with RT.

After that, I installed again Ubuntu 20 on the Up squared and installed the debian packages of my previously compiled RT-upboard-patched kernel and now it works. I can control the GPIO and the leds.

fvllml

I am trying now the kernel proposed by the wiki.

up@up:~$ uname -a
Linux up 5.4.0-1-generic #0~upboard5-Ubuntu SMP Fri Jan 7 11:53:57 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

Now I can see the leds and control the GPIO pins.

Am I compiling the right kernel or should I use another repository?

fvllml

Doing a diff on lsmod for both kernels I got this:

# Modules lodaded on generic but not in realtime
snd_sof_intel_hda      20480  1 snd_sof_intel_hda_common
leds_upboard           16384  0
pinctrl_upboard        16384  0
ulpi                   20480  1 dwc3
upboard_fpga           20480  0

# Modules loaded on realtime but not in generic
snd_soc_hdac_hda       20480  1 snd_sof_intel_hda_common
pinctrl_broxton        40960  0

So basically the kernel with the realtime patch is not loading pinctrl_upboard and leds_upboard so I think this is why I cannot control the GPIOs.

When trying to load them manually:

up@up:~$ modprobe -v pinctrl_upboard
modprobe: FATAL: Module pinctrl_upboard not found in directory /lib/modules/5.4.65-rt38+
up@up:~$ modprobe -v leds_upboard
modprobe: FATAL: Module leds_upboard not found in directory /lib/modules/5.4.65-rt38+

Any way I could have those modules on a realtime patched kernel?

fvllml

When I do a diff on the output of lsmod from both kernels I get this

# Modules lodaded on generic but not in realtime
snd_sof_intel_hda      20480  1 snd_sof_intel_hda_common
leds_upboard           16384  0
pinctrl_upboard        16384  0
ulpi                   20480  1 dwc3
upboard_fpga           20480  0

# Modules loaded on realtime but not in generic
snd_soc_hdac_hda       20480  1 snd_sof_intel_hda_common
pinctrl_broxton        40960  0

Apparently the pinctrl_upboard and the leds_upboard are not being loaded so I think this is why I cannot control the GIPOs on my up squared.

If I try to load them I get the following error

up@up:~$ modprobe -v pinctrl_upboard
modprobe: FATAL: Module pinctrl_upboard not found in directory /lib/modules/5.4.65-rt38+
up@up:~$ modprobe -v leds_upboard
modprobe: FATAL: Module leds_upboard not found in directory /lib/modules/5.4.65-rt38+

Also, on the realtime kernel I can find the .ko files for leds and pinctrl at

up@up:/lib/modules/5.4.0-1-generic$ find . | grep -i leds-upboard
./kernel/drivers/leds/leds-upboard.ko
up@up:/lib/modules/5.4.0-1-generic$ find . | grep -i pinctrl-upboard
./kernel/drivers/pinctrl/pinctrl-upboard.ko

with no chances on /lib/modules/5.4.65-rt38+

Any way I can have an Ubuntu with realtime patched kernel and working GPIOs on Up squared?