[Letux-kernel] Memory freeze and timing CI20

H. Nikolaus Schaller hns at goldelico.com
Mon Feb 15 12:12:19 CET 2021


Hi,
sorry for the delay on my side now...

> Am 11.02.2021 um 16:15 schrieb Zhou Yanjie <zhouyanjie at wanyeetech.com>:
> 
> Hi Nikolaus,
> 
> 
> Sorry, I got caught up in other thins last few weeks.
> 
> 
> On 2021/2/5 下午2:53, H. Nikolaus Schaller wrote:
>> Hi,
>> I got a hint from a member of the Pyra community who had been following
>> the OMAP5 + DDR3 timing issues, that the jz4780/CI20 may have similar issues.
> 
> 
> Could you describe the specific phenomenon?

I do not know more than described in the pull request description 

>> https://github.com/MIPS/CI20_u-boot/pull/18

The author says

"This fixes a few timing errors in the memory initialization routine, specifically the minimum self-refresh time which was too low for both Samsung and Hynix chip, as well as the four bank activation time and the exit-power-down-to-active-command delay for the Samsung ones. The changes are based on the memory chips' most recent datasheets as well as the JZ4780 manual and have fixed all memory-related freezes I've been experiencing with my board."

But I haven't observed memory related issues myself. BTW it is not clear how to
easily distinguish that from other freezes.

What we had was a memory timing issue on the omap5. There stability did clearly depend
on the installed memory chips (there were two variants) and tweaking the memory timings
did fix it for all. It had something to do with automatic timing measurements and corrections
of the DDR3 chips. This was not enabled correctly on omap5.

>  And witch version u-boot do you use?

I use this u-boot: 

https://git.goldelico.com/?p=letux-uboot.git;a=shortlog;h=refs/heads/ci20-v2013.10

seems to be a 2013.10 u-boot with a lot of fixes up to 2017.

> 
> It seems that now the u-boot mainline (after version 2019.01) also supports CI20.

So it could be that the mainline u-boot already includes the patch

https://github.com/MIPS/CI20_u-boot/pull/18/commits/3c4bdbd749edc344abf11823282363d79c1d5eeb
> 
> 
>> I am not sure if it is needed or not since my board works well without - except
>> the freezes I had observed with SMP but I did not relate this to memory timing.
>> 
>> There is a patch floating around:
>> 
>> https://github.com/MIPS/CI20_u-boot/pull/18
>> 
>> I have checked an in my U-Boot it is not included but could be added.
>> 
>> What do you think?
>> 
>> BTW: what is the status of the SMP / Cache driver?
> 
> 
> It seems to work normally based on 5.10.7, I will send it to you later.

Fine and thanks!

> Happy Chinese New Year!

BR and same to you,
Nikolaus



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