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Syslog message: TCBC I2C accelerator error: and CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC x on MX2K

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Article ID: KB30474 KB Last Updated: 23 Jul 2015Version: 1.0
Summary:

This article describes the meaning of the following I2C-related error messages in the syslog:

MX2K-re0 /kernel: tcbc i2c accelerator error: master 1 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 1) group 0xf device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 1 ([0xf, 0x20] -> 0x0)

Symptoms:

The TCBC I2C error and CHASSISD_I2CS_READBACK_ERROR messages display on MX2K platforms in Junos OS Release 14.2R3. The message is logged to an empty LC slot upon committing the configuration. This log means that TCBC (Tiny Control Board Control FPGA) errors occur due to an I2C timeout. The I2C device (LC Slot 1 shown in the trace snippet below) cannot be read during the specified time and a timeout occurs. This status is obtained by reading a hardware register that shows that the data 1 valid bit is not set and returns the error code 0 for the timeout.

MX2K-re0 /kernel: tcbc i2c accelerator error: master 1 entry 255 data 1 not valid. Err code (0) ------> I2C read timeout
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 1) group 0xf device 0x54 bytes 1 err 5 -----> I/O error
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 1 ([0xf, 0x20] -> 0x0)

As seen in the following entire traces, multiple LC slots are tried in the same manner and the read fails. We can see these errors for empty LC slots. When valid I2C data is available, we do not see the errors. Since these errors are printed in the software but the information is coming from hardware registers, printing the errors in the log cannot be avoided. Similarly, the readback error means the chassisd could not read back information from the I2C slave, and if it fails it will be logged. These errors do not cause any harm, so we can safely ignore them in the logs.

[edit]
lab@MX2K-re0# set interfaces xe-7/0/1.0

[edit]
lab@MX2K-re0# show |compare
[edit interfaces]
+ xe-7/0/1 {
+ unit 0;
+ }

[edit]
lab@MX2K-re0# commit
commit complete

lab@MX2K-re0>
*** messages ***
MX2K-re0 /kernel: tcbc i2c accelerator error: master 1 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 1) group 0xf device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 1 ([0xf, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 3) group 0x3 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 3 ([0x3, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 4) group 0x4 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 4 ([0x4, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 5) group 0x5 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 5 ([0x5, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 6) group 0x6 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 6 ([0x6, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 1 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 8) group 0x8 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 8 ([0x8, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 1 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 1) group 0xf device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 1 ([0xf, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 3) group 0x3 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 3 ([0x3, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 4) group 0x4 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 4 ([0x4, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 5) group 0x5 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 5 ([0x5, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 0 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 6) group 0x6 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 6 ([0x6, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 1 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 8) group 0x8 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 8 ([0x8, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 10) group 0x20 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 10 ([0x20, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 11) group 0x21 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 11 ([0x21, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 12) group 0x22 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 12 ([0x22, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 13) group 0x23 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 13 ([0x23, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 14) group 0x24 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 14 ([0x24, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 15) group 0x25 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 15 ([0x25, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 16) group 0x26 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 16 ([0x26, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 17) group 0x27 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 17 ([0x27, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 5 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 18) group 0x28 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 18 ([0x28, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 5 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 19) group 0x29 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 19 ([0x29, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 10) group 0x20 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 10 ([0x20, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 11) group 0x21 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 11 ([0x21, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 12) group 0x22 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 12 ([0x22, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 13) group 0x23 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 13 ([0x23, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 14) group 0x24 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 14 ([0x24, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 15) group 0x25 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 15 ([0x25, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 16) group 0x26 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 16 ([0x26, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 4 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 17) group 0x27 device 0x54 bytes 1 err 5
MX2K-re0 mgd[1889]: UI_COMMIT_COMPLETED: commit complete
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 17 ([0x27, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 5 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 18) group 0x28 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 18 ([0x28, 0x20] -> 0x0)
MX2K-re0 /kernel: tcbc i2c accelerator error: master 5 entry 255 data 1 not valid. Err code (0)
MX2K-re0 /kernel: tcbc i2c accelerator error: Read failed for (LC Slot 19) group 0x29 device 0x54 bytes 1 err 5
MX2K-re0 chassisd[1744]: CHASSISD_I2CS_READBACK_ERROR: Readback error from I2C slave for FPC 19 ([0x29, 0x20] -> 0x0)

Note: FPC 1, 3-6, 8, and 10-19 are empty slots on this chassis configuration.

Cause:

The MX2K Junos OS software tries to check the allotted power for all of the FPCs; here in the CHASSISD_I2CS_READBACK_ERROR logs, it shows for the FPCs that are not present in the chassis. It just reads the I2C device and fails there as those FPCs slots are blank, then prints those readback errors.

Solution:

In 14.2R3, we can see these errors for empty LC slots by committing the configuration. This is resolved in 14.2R4 by fixing PR1075643. These errors are cosmetic and do not cause any harm, so we can avoid unnecessary RMAs by recognizing that this error message does not indicate I2C hardware failure.

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