DDR timing for vendor board

[Jack Mitchell]

On 08/12/2022 04:01, Rob Kramer wrote:
> Hi all,
> 
> I have a RK3288 board from a Chinese display vendor that came with the
> usual giant Rockchip tarball that they patched here and there to make
> the board work. It seems to be based on a rk3288-evb, since that is what
> they patched in the kernel. The kernel is a 4.4 kernel with Android
> stuff in it (i.e. fiq-debugger) and a large amount of Rockchip patches,
> u-boot is 2017.09, with rk patches.
> 
> It turns out that u-boot TPL/SPL won't boot because the DDR timings are
> incorrect, and the Chinese vendor uses the Rockchip
> rk3288_ddr_400MHz_v1.09.bin loader. I'm using u-boot 2022.01 for now,
> and I've tried to naively modify the timing in
> arch/arm/dts/rk3288-evb.dts, but it doesn't work at all, with varying
> errors on boot.
> 
> The Rockchip loader provides the following info when booting:
> 
>   In
>   Channel a: DDR3 400MHz
>   Bus Width=32 Col=10 Bank=8 Row=15 CS=1 Die Bus-Width=16 Size=1024MB
>   Memory OK
>   OUT
>   Boot1 Release Time: Apr 11 2018 10:32:58, version: 2.36
>   ChipType = 0x8, 232
> 
> I've tried various DDR3 (not LPDDR3) settings from other boards, for
> example for a Firefly (666 MHz DDR3):
> 
>   U-Boot TPL 2022.01 (Jan 10 2022 - 18:46:34)
>   Col detect error
>   DRAM init failed!
>   ### ERROR ### Please RESET the board ###
> 
> It was expected that 666MHz doesn't work, but if I just change the
> frequency in the dts, that also fails (error -22).
> 
> How can I support the DDR for this board? I can't even see what the ID
> on the chips is, because the heatsink is blocking sight and seems to be
> attached with some sort of thermal glue.
> 
> Is there a way to read back the DDR timings (phy-timing, sdram-params)
> from the kernel/SoC on a board that is booted using the proprietary loader?
> 
> Cheers!
> 
>     Rob
> 

Hi Rob,

You could be in for a world of hurt here as Rockchip are very poor at
supporting different DDR init configurations in u-boot. In the past with
awkward boards I've used the Rockchip DDR init blob as the TPL binary
for u-boot then skip the DRAM init in the u-boot SPL.

>From my travels in this area I've found that single channel RAM boards
are particularly difficult to get working as the majority if not all
mainlined board use dual channel RAM.

Sorry I can't be more help, but trying to use the DDR blob is a good
starting point to get you going on mainline.

Good Luck!

-- 
Jack Mitchell, Consultant
https://www.tuxable.co.uk