I2C1

[evilwulfie]

Its good that the I2C busses are now using the same number for each bus
in hardware and software.
But I am seeing something weird with the I2C1 bus.

If i use i2cdetect on bus 0 and 2 the bus scan is very fast and i see
the things i expect from past scans on
older linux versions.

But if i scan I2C1 (i2cdetect -r 1) I can almost go get a cup of coffee
while it scans the bus.
I also do not see anything i would expect out there that i have added to
the bus.

It behaves the same way ( on a BBG ) whether the board is plugged in to
my board or not plugged into anything.

I was wondering if there might be a reason why the different busses
behave so different.

I have a RTC as well as a cape eeprom on I2C2 and they are all
accessible normally.

Just that pesky I2C1 bus.

image used is latest from  
http://debian.beagleboard.org/images/bone-debian-9.3-iot-armhf-2018-01-28-4gb.img.xz

[evilwulfie]

Can anybody with a green or black verify the odd behavior i am seeing on
my greens and blacks ?

I am using the latest IOT image

root@beaglebone:/home/debian# uname -r
4.9.78-ti-r94


I use i2ctools and issue the commands

root@beaglebone:/home/debian# i2cdetect -r 0
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-0 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n] y
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: UU -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
root@beaglebone:/home/debian# i2cdetect -r 2
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-2 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n] y
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
root@beaglebone:/home/debian# i2cdetect -r 1
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-1 using read byte commands.
I will probe address range 0x03-0x77.
Continue? [Y/n] y
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- ^C
root@beaglebone:/home/debian# uname -r


Doing the last command there  (  i2cdetect -r 1  )
Its S L O W as heck. reading bus 0 or 2 is fast as it always has been.



This happens on a green or black and whether its just standalone or on
an expansion board.

I see this happen with the last 3 software versions
http://debian.beagleboard.org/images/bone-debian-9.3-iot-armhf-2018-01-28-4gb.img.xz
https://debian.beagleboard.org/images/bone-debian-9.2-iot-armhf-2017-10-10-4gb.img.xz
http://debian.beagleboard.org/images/bone-debian-9.1-lxqt-armhf-2017-08-31-4gb.img.xz

anything earlier and I2C1 is not enabled by default and not tested by me