[U-Boot] mx6ul_14x14_evk

[Fabio Estevam]

Hi Eric,

On Sun, Aug 28, 2016 at 6:04 PM, Eric Nelson <eric at nelint.com> wrote:
> On 08/28/2016 01:59 PM, Eric Nelson wrote:
>> Hi Fabio, Peng, and all.
>>
>> I just ran into a problem with bus frequency switching
>> on the EVK and there appears to be a U-Boot component.
>>
>> Using the 4.1.15 kernel from git.freescale.com (commit a4d2a08)
>> and the latest U-Boot from Stefano's imx tree (commit a3e5519)
>> causes the EVK to hang during a bus frequency switch to LOW_POWER
>> mode.
>>
>> The last gasp is this:
>>       Bus freq set to 24000000 start...
>>
>> And the code block in question is here:
>>       http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/arch/arm/mach-imx/busfreq_ddr3.c?h=imx_4.1.15_1.0.0_ga#n386
>>
>> When using the binary U-Boot 2015.07 from the EVK package (commit
>> d7d7c43 from git.freescale.com), the kernel gets through the
>> frequency switch and produces this message.
>>
>>       Bus freq set to 24000000 done!
>>
>> I first saw this problem with u-boot-fslc branch v2016.07
>> and linux-fslc (4.1.29 and 4.1.30).
>>
>> Has anybody else experienced this?
>>
>
> I forgot to mention it, but this is easy to reproduce
> by downing both ethernet interfaces and blanking the
> display.
>
>         ifconfig eth0 down
>         ifconfig eth1 down
>         echo 1 > /sys/class/graphics/fb0/blank

I was able to reproduce this problem here.

The major difference between mainline U-Boot and NXP U-Boot is that
mainline U-Boot uses SPL and NXP U-Boot uses imximage.cfg to configure
the DDR.

I have just created and tested the patch below against Stefano's tree:
http://pastebin.com/crAe1Yr1

, which basically uses imximage.cfg from NXP U-Boot instead of SPL and
the hang does not occur.

It seems to me that we need to carefully review the SPL DDR init code
in mainline in order to fix this problem.

I will try to take a look at it tomorrow, but if anyone spots the DDR
problem in the SPL code, then feel free to submit the patch :-)

Thanks,

Fabio Estevam