Trying to boot custom kernel on Wink Hub (i.MX28)

[Fabio Estevam]

Hi Rogan,

On Tue, Aug 22, 2023 at 6:42 AM Rogan Dawes <rogan at dawes.za.net> wrote:
>
> Hi Fabio,
>
> As far as I am aware, the U-boot source for the Wink hub has not been
> made available anywhere. That said, the RAM chip in use on the board

Was there a formal request for the U-Boot source code to Wink?

As per the GPL license, they have to share the U-Boot source code.

> is marked D9LPX, which apparently corresponds to the following item:
> https://media-www.micron.com/-/media/client/global/documents/products/data-sheet/dram/ddr2/512mbddr2.pdf?rev=2c70f8a2b207452584b2bf040de8d771

There is a tool from NXP that helps with the i.MX28 DDR2 controller
initialization for a specific DDR model:

https://community.nxp.com/pwmxy87654/attachments/pwmxy87654/imx-processors/9552/1/MX28_DDR2_register_programming_aid_v0.2.xlsx

The DDR initialization values obtained from this tool are then used in
U-Boot inside the 'mxs_dram_vals' array.

There is a common DDR configuration at
arch/arm/cpu/arm926ejs/mxs/spl_mem_init.c.

Most likely, in your case, it will require a custom mxs_dram_vals
initialization, like it is done at board/liebherr/xea/spl_xea.c.

> I did try to change the iomux_cfg_t as suggested above, built using
> make mx28evk_defconfig && make u-boot.sb, and used mxsldr to try load
> it, to no avail. There was no output on the serial port at all, or any
> other suggestion that anything was running.

It has been a long time since I used the mxsldr tool.

When time permits, I can try to load a recent U-Boot over USB using
this tool on a imx28-evk.

Cheers