QCVS-DDRV passed but Linux kernel crash ?

[stefanvranken]

Hello,

My board has P2020 with 1GByte discrete ddr3 (4 sdrams* 128Mx16). We now have 30 boards of which 3 show unstable behaviour: uboot ok but linux crashes due to kernel oops (bus-, paging-, segmentation- errors) indicating unstable instruction fetches from ddr3.

With Codewarrior-tap I ran DDRValidation tool on these 3 boards and all 3 are validated ok:  ddr operational testing of full 1GByte does not show errors.   However, running linux from ddr3 is unstable ?  
P2020 DDR data rate = 666.66 Mbps (ddrclkin=66,666 Mhz*10)  >> ddr_mck = 333.33 Mhz
On one board I changed this to  600 Mbps datarate (ddrclkin=100M*6) >> ddr_mck = 300 Mhz but stays unstable.

Could it be that some ddr3-sdram configuration parameter is causing trouble if fast consecutive burst accesses (linux, dual core) , while cw-tap-ddrv access is less stringent ?

Kind Regards

Stefan

[stefanvranken]

In the mean time I have discovered one ddr-controller-parameter that can make my unstable protos good.

This new setting is now under test on all prototypes but this is definitely a better ddr-controller setting for my boards.

You can add next info to the ticket.

parameter “timing_cfg1[29:31 wrtord]”

tWTR min = greater of 4CK or 7.5ns (Micron datasheet & CK=333Mhz_3.0ns)

WRTORD = 4CK  min <<<<

WRTORD = (tWTR+2cycles) if ddr_sdram_cfg2[OBC_CFG]=1 >> tWTR min = 4+2=6

“OBC: On_the_fly_Burst_chop” is not used >> parameter WRTORD = 4  (in my old reg-settings).   <<< Correction 4jan18: OBC=on, explaining unstability

As soon as I make WRTORD > 4 ,  the unstable protos become stable.

To create max margin max setting 7 ck is used.

#define CONFIG_SYS_DDR_TIMING_1                0xBCBBE747       /* caslat=6,wrrec=7,wtr=7 */

#define CONFIG_SYS_DDR_MODE_1                   0x00041621        /* sdram:caslat=6,wrrec=7,Rtt=60,ods=half */

[stefanvranken]

Case 00139557

[ufedor]

It will be more convenient if you create a Technical Case to investigate the issue:

https://community.freescale.com/thread/381898