[SOLVED] iMX6 : I2C2_SCL goes permanently low at Linux boot

[dplamp]

Hi,

I bought :

• a processor board with a iMX6Q
• development board.

I tested I2C1 and I2C2 with the processor board on the development board with i2cdetect, and it sees all connected chips on both buses.

Then I made my own board. I2C1 passes the test. But at some point, while the Linux kernel is loading, the I2C2_SCL line goes low, and stays low forever. I2C2_SDA is high all the time. A reboot doesn't bring SCL back high again, only a power cycle. When I take the processor board from my home made board to the development board, I2C2 works OK.

What I did on my home made board :

• checked the 4.7K pull-up resistors on SCL and SDA lines to +3.3V : OK
• checked short circuits : didn't find any...
• unsoldered the 3 chips on I2C2 (RTC, GPIO expander and DAC) : the iMX6Q is on its own on I2C2
• toggled the I2C2_SCL (KEY_COL3) and I2C2_SDA (KEY_ROW3) in U-Boot : OK
• checked registers configurations in Linux :
  • pad mux registers (0x20e0210, 0x20e0214) both read 0x00000014
  • control registers (0x20e05e0, 0x20e05e4) both read 0x0001B8B1
• disabled drivers like the RTC's, which is on I2C2 on both the development and home made board

So, now, I'm desperately running out of ideas...

Regards

[dplamp · Accepted solution]

**bleep** it ! That was a shortcut to the next pin configured as a SPI chip select. Hence the pin pulled low at Linux boot.

[igorpadykov]

Hi dplamp

one can try to narrow down issue, if this is caused by hardware or linux running baremetal sdk test

https://github.com/RT-Thread/rt-thread/tree/master/bsp/imx6sx/iMX6_Platform_SDK/sdk/drivers/i2c

https://community.nxp.com/t5/i-MX-Processors/SMP-Enable-in-IMX6/m-p/542111

Best regards
igor