[Letux-kernel] [PATCH 2/3] DT: EVM: add LEDs

H. Nikolaus Schaller hns at goldelico.com
Wed Sep 28 08:49:30 CEST 2016


> Am 28.09.2016 um 05:37 schrieb Tony Lindgren <tony at atomide.com>:
> * H. Nikolaus Schaller <hns at goldelico.com> [160927 13:11]:
>>> Am 27.09.2016 um 21:49 schrieb Tony Lindgren <tony at atomide.com>:
>>> How about this for defaults:
>>> - heartbeat for led3
>>> - cpu0 for led4
>>> - cpu1 for led5
>> Good idea. Will try.
>> What I don't exactly know is if these gpios based on an I2C-expander
>> can handle cpu activity triggers or if they are locked up if this i2c
>> processing triggers another cpu activity...
> Oh right, if the GPIOs are on the i2c bus

yes, they are all gpio9 which is the tca6424 on i2c5.

> it's probably not a good
> idea :) Or at least will be inaccurate if the bus can sleep.

I have tested a little by writing to /sys/class/leds/.../trigger.

If I make one LED trigger by "cpu0" it is always on and if I make
a second one triggered by "cpu1" the heartbeat becomes irregular.

So indeed this does not work.


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