imx8m ic2 reset

[ricardo_fernandes]

Hi.

I founded that many times after long time (could be days, weeks or months) the ic2 bus 1 stops to work properly.

When it's working properly I have:

> i2cdump -y 1 0x50
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f 0123456789abcdef
00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

> i2cget -y 1 0x50 0
0x00

When it's not working properly I have:

> i2cdump -y 1 0x50
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f 0123456789abcdef
00: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
10: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
20: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
30: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
40: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
50: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
60: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
70: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
80: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
90: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
a0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
b0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
c0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
d0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
e0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
f0: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX

> i2cget -y 1 0x50 0
Error: Read failed

If I reboot the device it starts to work ok again.

Is there a command to reset ic2?

I need to understand what's causing it but I would like also to check if is possible to fix it just by executing a simple command.

Thanks in advance.

RF

[ricardo_fernandes]

Hi.

Thanks for your reply.

Yes, indeed it's a custom board.

Sounds bad right?

Best regards.

[Alejandro_Salas]

The first thing that you can check is that slave device with your 0x50 slave address. Your hardware connection. But as the issue is in a random times, check just when the issue is present.

Best regards.

[ricardo_fernandes]

Hi.

I don't have physical access to the device only remote. I know that is not a bad connector because when I reboot the device it fixes it.

Is there any command that I can execute in order to restart the I2C? Alternatively I can create a small C service and run to restart it but I'm not sure if is possible with the API.

Remotely I cannot do a lot...

If I don't find a solution I will create a workaround to reboot the device when it happens....but this is not a fix is just a temporary workaround.

Best regards.

[Alejandro_Salas]

Hello, 

Unfortunately, it is not possible to reset the I2C bus from the Linux OS (Does not exist any command to do it). But, when it happens, I am guessing you have the issue only in the slave and not in all the BUS.

About of reset by software, I believe that is possible, you can check the reference manual, for the IMX8M in the section 16.1.4.8 is described the two ways to do a reset in the I2C bus.

You must check the I2C_I2CR register, exactly the IEN bit.

Best regards!

[ricardo_fernandes]

Many thanks.

I'll try the reset.

Best regards.

[Alejandro_Salas]

Hello!

That issue occurs when the I2C bus do not recognize the slave or in other words, the slave do not acknowledge the slave address.

For example, in my case I am using an IMX8MN and when I set the command i2cdetect 1:

I have that slaves connected in the BUS.

If I set the command i2cdump -y 1 0x52:

I had the expected.

But if I try with the 0x53 slave (Not in the BUS):

I had the same log that to have.

So, that make me think that the problem is in the slave device. 

Are you using a custom board?

Best regards.