Good day,

I use prebuild Armbian Stretch mainline kernel 4.14.y. And I want to connect pcf8563 rtc through i2c protocol on TWI1_SCK/PB18, TWI1_SDA/PB19 hw A20 pins. pcf8563 slave address is 0x51. If by default, no i2c are enabled through overlays= in armbianEnv.txt,  I still get i2c-1 device with addresses 0x51-0x57 occupied:

root@lime2:~# ls /dev | grep i2c
i2c-0
i2c-1
root@lime2:~# i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
30: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- --
root@lime2:~# i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
50: UU UU UU UU UU UU UU UU -- -- -- -- -- -- -- --

If I enable i2c1 through overlays=i2c1 in armbianEnv.txt, i2c-0 disappears from /dev/ and axp209 is now mapped on i2c-2:

root@lime2:~# ls /dev | grep i2c
i2c-1
i2c-2
root@lime2:~# i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
50: UU UU UU UU UU UU UU UU -- -- -- -- -- -- -- --
root@lime2:~# i2cdetect -y 2
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
30: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- --

Please advice, how to free up slave address 0x51 on i2c1? Additional info with i2c1 enabled:

root@lime2:/# ls /sys/bus/i2c/devices/
1-0050  1-0051  1-0052  1-0053  1-0054  1-0055  1-0056  1-0057  2-0034  i2c-1  i2c-2
root@lime2:/# cat /sys/bus/i2c/devices/1-0051/modalias
i2c:dummy
root@lime2:/# grep dummy /lib/modules/4.14.65-sunxi/modules.alias
alias rtnl-link-dummy dummy
root@lime2:/# rmmod rtnl-link-dummy
rmmod: ERROR: Module rtnl_link_dummy is not currently loaded
root@lime2:/# dmesg | grep dummy
[    1.063542] ldo1: supplied by regulator-dummy
[    1.063827] ldo2: supplied by regulator-dummy
[    1.064960] ldo3: supplied by regulator-dummy
[    1.065662] ldo4: supplied by regulator-dummy
[    1.065854] ldo5: supplied by regulator-dummy
[    1.066504] dcdc2: supplied by regulator-dummy
[    1.067189] dcdc3: supplied by regulator-dummy
[    1.398296] usb_phy_generic usb_phy_generic.0.auto: usb_phy_generic.0.auto supply vcc not found, using dummy regulator

 

Solved: i2c1 address 0x50 through 0x57 are used by onboard EEPROM connected to PB18, PB19

root@lime2:~# cat /sys/bus/i2c/devices/1-0050/modalias
i2c:24c16
root@lime2:~# grep 24c16 /lib/modules/4.14.65-sunxi/modules.alias
alias i2c:24c16 at24
root@lime2:~# rmmod at24
root@lime2:~# i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
50: 50 51 52 53 54 55 56 57 -- -- -- -- -- -- -- --