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

[Rogan Dawes]

Hi Fabio,

On Tue, 22 Aug 2023 at 13:44, Fabio Estevam <festevam at gmail.com> wrote:
>
> 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.
>

I have just asked them for it, so let's see what happens. I'm not
optimistic, though, given their financial troubles. I am not aware of
anyone else asking them. However, I do believe that there have been
requests for the kernel sources for the Wink Hub 2, which were
ignored, suggesting that they are not the best GPL citizen.

> > 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

I think fiddling with RAM timings is a little more in the weeds than I
am ready to go at this point. I did see this post
(http://web.archive.org/web/20151005053615/http://jalderman.org/?p=348),
suggesting that it was not too difficult to get it working using
mainline u-boot. That said, I also note that some teardowns mention
that the RAM is a Nanya part, while I have Micron, so perhaps I should
not place too much reliance on that.

Rogan