Hello!
Please consider if I made something wrong, sending this issue. This is
my first contact to the LKML.
By mistake, I accessed an LED via /sys/class/leds subsystem very fast in
an user application. I figured out, that the free user memory decreased
constantly. So I tried to analyze the Problem and wrote a litte script:
#!/bin/sh
while [ 1 ]; do
echo 1 > /sys/class/leds/2a_service_yellow/brightness
echo 0 > /sys/class/leds/2a_service_yellow/brightness
done
And voila, I was able to reproduce the problem.
So I add a bit more debugging:
#!/bin/sh
cnt=0
while [ 1 ]; do
if [ `expr $cnt % 1000` -eq 0 ]; then
free | grep Mem: | cut -d' ' -f25
fi
echo 1 > /sys/class/leds/2a_service_yellow/brightness
echo 0 > /sys/class/leds/2a_service_yellow/brightness
let "cnt++"
done
And huh? No memory is eaten anymore. So it looks like, the problem only
occours on heavy (fast) usage of /sys/class/leds subsystem.
I rewrote the script and toggled a GPIO pin, but there was no problem
recognizable.
Some details about my test environment:
Hardware: Ti Sitara AM3357ZCZ with 128MiB memory
Kernel: vanilla 4.6
The relevant part of my .dts:
#include "am33xx.dtsi"
/ {
...
cpus {
cpu@0 {
cpu0-supply = <&dcdc2_reg>;
operating-points = <
/* kHz uV */
800000 1300000
600000 1112000
300000 969000
>;
};
};
memory {
device_type = "memory";
reg = <0x80000000 0x08000000>; /* 128 Mib */
};
...
leds {
pinctrl-names = "default";
pinctrl-0 = <&user_leds_s0>;
compatible = "gpio-leds";
...
led2 {
label = "2a_service_yellow";
gpios = <&gpio1 2 GPIO_ACTIVE_HIGH>;
linux,default-trigger = "2a_service_yellow";
default-state = "off";
};
...
};
...
};
&am33xx_pinmux {
pinctrl-names = "default";
pinctrl-0 = <&gpio_misc_pins>;
...
user_leds_s0: user_leds_s0 {
pinctrl-single,pins = <
...
0x24 (PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* (T10)
gpmc_ad9.gpio0[23] */
>;
};
...
};
...
Kind regards
Daniel
