ddr3 calibration error-strange write leveling result

[jiangtao]

Hi,All

We encountered some question in DDR3.We have produced about 1 thousand boards,and we got several (5~6) board fail to boot from EMMC,after checked the DDR3,we found ddr3 caused the booting failing.

our DDR3 device is :

IS43TR16256A-15HBLI

I used the ddr stress test tool v2.6 to test one of our faulted custom board，I got some strange results in HW write leveling process.

ddr_mr1=0x00000004
Start write leveling calibration...
running Write level HW calibration
Write leveling calibration completed, update the following registers in your initialization script
MMDC_MPWLDECTRL0 ch0 (0x021b080c) = 0x001F001F
MMDC_MPWLDECTRL1 ch0 (0x021b0810) = 0x001F001F
MMDC_MPWLDECTRL0 ch1 (0x021b480c) = 0x001F001F
MMDC_MPWLDECTRL1 ch1 (0x021b4810) = 0x001F001F
Write DQS delay result:
Write DQS0 delay: 31/256 CK
Write DQS1 delay: 31/256 CK
Write DQS2 delay: 31/256 CK
Write DQS3 delay: 31/256 CK
Write DQS4 delay: 31/256 CK
Write DQS5 delay: 31/256 CK
Write DQS6 delay: 31/256 CK
Write DQS7 delay: 31/256 CK

Starting DQS gating calibration
. HC_DEL=0x00000000 result[00]=0x11111111
. HC_DEL=0x00000001 result[01]=0x11111111
. HC_DEL=0x00000002 result[02]=0x11111111
. HC_DEL=0x00000003 result[03]=0x11111111
. HC_DEL=0x00000004 result[04]=0x11111111
. HC_DEL=0x00000005 result[05]=0x11111111
. HC_DEL=0x00000006 result[06]=0x11111111
. HC_DEL=0x00000007 result[07]=0x11111111
. HC_DEL=0x00000008 result[08]=0x11111111
. HC_DEL=0x00000009 result[09]=0x11111111
. HC_DEL=0x0000000A result[0A]=0x11111111
. HC_DEL=0x0000000B result[0B]=0x11111111
. HC_DEL=0x0000000C result[0C]=0x11111111
. HC_DEL=0x0000000D result[0D]=0x11111111
ERROR FOUND, we can't get suitable value !!!!
dram test fails for all values.

Error: failed during ddr calibration

The DQS group's write leveling delay results is the same :31/256 CK delay. the nomarl board 's results is below:

Write leveling calibration completed, update the following registers in your initialization script

    MMDC_MPWLDECTRL0 ch0 (0x021b080c) = 0x004E004E

    MMDC_MPWLDECTRL1 ch0 (0x021b0810) = 0x0041004A

    MMDC_MPWLDECTRL0 ch1 (0x021b480c) = 0x002B0029

    MMDC_MPWLDECTRL1 ch1 (0x021b4810) = 0x002D0041

Write DQS delay result:

   Write DQS0 delay: 78/256 CK

   Write DQS1 delay: 78/256 CK

   Write DQS2 delay: 74/256 CK

   Write DQS3 delay: 65/256 CK

   Write DQS4 delay: 41/256 CK

   Write DQS5 delay: 43/256 CK

   Write DQS6 delay: 65/256 CK

   Write DQS7 delay: 45/256 CK

I read the manual " 45.11.6.1 Hardware Write Leveling Calibration"

every DQS write leveling should repeat step 5~7 and adds 1/8 cycle delay between DQS and clk every times,then fine tuning must be executed to find precise delay value ,the resolution of the tuning is 1/256 clk.

What clues can we get through this result?

does the 31/256 results mean that write leveling only execute the first 5~7 step then the ddr device sampled the CLK and got the transition from 0 to 1,then tuining the result to 31cycles?

[igorpadykov]

Hi jiang

0x001F001F means can't find the write leveling value, one can increase WALAT and
drive strength of DQS,DQ signals. Description can be found in AN4467 i.MX 6 Series DDR Calibration
http://www.nxp.com/docs/en/application-note/AN4467.pdf
In general it may mean that ddr interface is not working at all and one can follow
bringup guidelines using i.MX6 System Development User’s Guide and check signals with

oscilloscope
http://cache.freescale.com/files/32bit/doc/user_guide/IMX6DQ6SDLHDG.pdf

Best regards
igor
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