[U-Boot] ROCK64 fails to boot using U-Boot TPL

[Simon South]

On 2019-09-24 12:54 p.m., Matwey V. Kornilov wrote:
> Simon, maybe you'll describe a way to obtain SD card image which you
> use? For the case if anybody wants to reproduce the issue in situ?

Sure---I'd love for other people to test this, and it's pretty easy 
since it doesn't require anything other than U-Boot itself.

Assuming the CROSS_COMPILE and BL31 environment variables are set up 
appropriately (I'm using ATF 2.1 from the mainline repository):

1. Switch to U-Boot's master branch and/or configure the source tree 
identically to my own with

      git checkout a9fa70b7b7167487affc5d919e541872c99e814b

2. Apply the attached patch, which enables the "mtest" command, with

      patch -p1 < rock64-enable-mtest.patch

3. Build U-Boot as usual:

      make distclean; rm -f ./idbloader.img
      make rock64-rk3328_defconfig all u-boot.itb

4. Write U-Boot to a microSD card as usual:

      sudo dd if=idbloader.img of=/dev/mmcblk0 seek=64
      sudo dd if=u-boot.itb of=/dev/mmcblk0 seek=16384

5. Place the microSD card in the ROCK64 and start it. Once the SPL 
loads, hit the spacebar to enter the shell and start the memory test with

      mtest

On my ROCK64, this immediately begins throwing off errors like

   FAILURE (read/write) @ 0x020014c0: expected 0x00000299, actual 
0x00000219)

and if I continue the boot process with "boot", the NetBSD kernel will 
load but panic almost immediately.

Note mine is a ROCK64 v2.0 with a 32Gb SpecTek LPDDR3 memory 
module---there is also a ROCK64 v3.0 and some variance in the memory 
chips used, so it could be this is limited to a specific model or 
production run.

Now here's what I've discovered lately:

Everything works normally if I have U-Boot TPL's set a slightly lower 
clock rate for the memory, by editing 
arch/arm/dts/rk3328-sdram-lpddr3-1600.dtsi and changing the "800" on 
line 27 to "766".

That suggests a hardware issue with my ROCK64, and in fact others have 
reported similar problems with the 2.0 version [1]. I'd be willing to 
leave it at that, except that if I also patch the (333MHz) Rockchip TPL 
to set a _higher_ clock rate for the memory, it continues to work just 
fine---all the way up to 933MHz!

So this is not just a hardware problem; there is some incompatibility 
between the RK3328 SDRAM driver as it exists in U-Boot and at least one 
group of ROCK64s in the world.

At the moment I'm still trying to identify what's different in the 
closed-source loader that causes it not to have this issue. Anyone have 
any thoughts?

[1] https://forum.pine64.org/showthread.php?tid=7387

-- 
Simon South
simon at simonsouth.net
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