imx6 Board Hangs suddenly

[sankarraj_sarav]

We have this issue on few of the built boards. Most of the boards are working fine.

Hardware details:

Imx6q.

The EHCI host controller is connected to USB hub – SMSC 2514. In which, an USB to serial controller is connected (EXAR XR21V1414IM48).

Linux kernel version: 4.9.88

U-Boot version: 2014.04 v7

We have done the DDR calibration and those values are put into the U-Boot. We used the U-Boot method, as mentioned in the link https://community.nxp.com/docs/DOC-105652 for DDR calibration.

We have ran the DDR calibration on different boards, the results are shown below.

MMDC_MPWLDECTRL0 (ch0)	0x00150013	0x0025001F	0x00150017	0x00180018	0x002E0030	0x0022001F	0x00190021	0x001C001B	0x00190017	0x0019001B	0x00170017
MMDC_MPWLDECTRL1 (ch0)	0x001D0018	0x002A0023	0x0021001A	0x0022001D	0x00300030	0x002B0028	0x00230019	0x0028001C	0x0023001E	0x0021001B	0x0026001F
MMDC_MPWLDECTRL0 (ch1)	0x00070019	0x0013001F	0x000E001C	0x00120021	0x000A001A	0x0015002A	0x00180027	0x000E0018	0x000C001D	0x00170027	0x000D001D
MMDC_MPWLDECTRL1 (ch1)	0x000A0019	0x00110026	0x0007001A	0x0007001C	0x00050012	0x001D001F	0x00110025	0x00040015	0x00000018	0x00140024	0x00000015
MPDGCTRL0 PHY0	0x431C0334	0x43200338	0x43240330	0x4324033C	0x43440358	0x457C060C	0x432C0344	0x43280334	0x43280338	0x432C033C	0x43300344
MPDGCTRL1 PHY0	0x031C0310	0x03200318	0x031C0310	0x031C0314	0x033C0334	0x06140618	0x032C031C	0x0328031C	0x03240318	0x03240318	0x03280318
MPDGCTRL0 PHY1	0x43280334	0x43200334	0x43200334	0x43200330	0x43340344	0x46380644	0x43280338	0x43200334	0x43200330	0x43280344	0x432C0338
MPDGCTRL1 PHY1	0x03280270	0x0328026C	0x031C0260	0x031C0264	0x03300270	0x057C054C	0x0328026C	0x0320026C	0x031C0268	0x03300270	0x03200264
MPRDDLCTL PHY0	0x463C3C3E	0x463A3E3E	0x483A3C3E	0x4E3E4042	0x4A404246	0x463E3A3A	0x4E3A3E42	0x4E3C3E40	0x4A3A3E3E	0x4A3A3C42	0x4A3A3E42
MPRDDLCTL PHY1	0x46463C4A	0x46463C4E	0x403E3A4C	0x403A384A	0x423E3C48	0x443A3C48	0x443E3648	0x42423A46	0x42443E4A	0x48443E4E	0x3E3E3A48
MPWRDLCTL PHY0	0x363A3C3A	0x363C3E3E	0x383C4040	0x363A3E3A	0x343E3E3C	0x3A3A403E	0x383E443E	0x343E423A	0x323C403C	0x363E3E3C	0x3A3E403C
MPWRDLCTL PHY1	0x48344A3A	0x46344A3E	0x4438483E	0x44324838	0x44364638	0x463C5042	0x4432443C	0x4234463C	0x463A4A40	0x42344A3E	0x4436483A

Test application being ran:

A test application is being run, this will write some data (12 bytes) continuously onto the USB to serial port.

The issue is on few boards, the system just hung (no output in the console). On few boards, there is some kernel panic/crash messages. These messages are not consistent, we get randomly.

Also, the issue reproducing time on a particular board varies from 5 mins to 3 hours.

We have tried disabling the DDR self-refresh, MMDCx_MDMISC Bit 16 (WALAT) is SET to 1, as posted in other threads and changing the kernel configuration to CONFIG_PREEMPT_VOLUNTARY, we see improvements. But, these stuffs  doesn’t fix the issue.

Our question:

1. Is there any known issues similar to this?
2. Any patches are available that can be tried?
3. Based on the provided table, what is the best DDR configuration to be used, to eliminate DDR issues?

[igorpadykov]

Hi Sankarraj

issue may be also caused by instable power supplies, ripples on power lines.

One can try linux memtester as it also well test not only memory but also

stresses power supplies. For checking power one can follow

i.MX6 System Development User’s Guide, sect.Table 2-6. Power and decouple recommendations,

ripple requirements.

https://www.nxp.com/docs/en/user-guide/IMX6DQ6SDLHDG.pdf

As an experiment one can try to hand solder 22uF capacitors directly under center of chip,
try software increase voltages of ARM_CAP, SOC_CAP, PU_CAP.

Best regards
igor
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------