Nanopi Neo I2C

[Ian Lepore]

On Sat, 2018-08-11 at 11:49 +0000, lyd mc via freebsd-arm wrote:
> Hi List,
> Can you help me make I2C work in this board?
> I can detect the controller but cannot access it through iic ioctl. 
> 
> root at nanopi-neo:~/prog/I2C # dmesg |grep iic
> iichb0: <Allwinner Integrated I2C Bus Controller> mem 0x1c2ac00-
> 0x1c2afff irq 34 on simplebus0
> iicbus0: <OFW I2C bus> on iichb0
> iichb1: <Allwinner Integrated I2C Bus Controller> mem 0x1c2b000-
> 0x1c2b3ff irq 35 on simplebus0
> iicbus1: <OFW I2C bus> on iichb1
> iichb2: <Allwinner Integrated I2C Bus Controller> mem 0x1c2b400-
> 0x1c2b7ff irq 36 on simplebus0
> iicbus2: <OFW I2C bus> on iichb2
> iic0: <I2C generic I/O> on iicbus0
> iic1: <I2C generic I/O> on iicbus1
> iic2: <I2C generic I/O> on iicbus2
> 
> kdump output:
> 
>   1290 mcp      NAMI  "/dev/iic0"
>   1290 mcp      RET   openat 3
>   1290 mcp      CALL  ioctl(0x3,I2CRDWR,0xbfbfecd4)
>   1290 mcp      RET   ioctl -1 errno 2 No such file or directory
> 
> This seems to work on my RPI.
> 

In this case, I wonder if the "errno 2" is not ENOENT, but
rather IIC_ENOACK which has not been translated to a proper errno
before returning. IIC_ENOACK is basically a timeout and can happen if
the slave address is wrong, or if the pinmux is wrong so that the bus
is electrically inactive.

Is the bus working in general? Do any devices show up on a scan with

  i2c -f /dev/iic0 -s

-- Ian