Re: [PATCH v2 7/8] arm: u8500: Switch Stemmy to upstream Janice device tree

On Mon, Aug 17, 2026 at 10:54:51PM +0200, Linus Walleij wrote:
> On Mon, Aug 17, 2026 at 6:45 PM Stephan Gerhold
> <[email protected]> wrote:
> 
> > Hm okay so you're basically dropping support for the internal eMMC in
> > this patch? Can we support both? BOOTSTD should be able to scan multiple
> > storages for boot targets.
> 
> Yeah just laziness on my part, I'll fix it up.
> 
> > I'm also not really sure about selecting Janice as "default" device tree
> > here. Do you expect users to change this setting when they want to build
> > stemmy for another board?
> 
> I have a script that loops over the Samsung device trees,
> and recompiles U-Boot for each of them.
> https://dflund.se/~triad/krad/makefiles/ux500-uboot.mak
> 
> > I wonder if we could continue using a single generic binary for all
> > boards using CONFIG_MULTI_DTB_FIT. We should have "fw_mach" in
> > board/ste/stemmy/stemmy.c that should tell us which device we are
> > running on, which seems to be mostly(?) unique:
> >
> > https://github.com/stericsson-mainline/android_kernel/blob/9508895090960012f916561b2ede5eaf8124fabd/arch/arm/tools/mach-types#L3956-L3965
> >
> > I'm not sure about codina-tmo, you would need to check which number the
> > bootloader passes.
> >
> > If these numbers are unique, it should be easy to implement
> > board_fit_config_name_match().
> 
> I see the appeal of the ambition to have a "one size fits (pun!) all"
> U-Boot.
> 
> But as it is, some of the DTS attributes on the external SD card are
> different between the platforms, so we would need to modify the
> U-Boot internal Stemmy device tree for those, copying over yet
> properties from the device trees and into the boardfile.
> 
> For example Janice and Codina uses a regulator for
> vqmmc-supply, and those using the "sd_level_translator"
> for vqmmc-supply actually use different GPIO pins on say
> Gavini compared to Codina or Golden.
> 
> The pin direction settings on the MMC host vary. (Some of
> these were really tricky to get right.)
> 
> So I think no, if we want external SD card boot we need
> per-device compiled U-Boot binaries with the unique device
> trees.
> 

I wasn't suggesting to use the same DT for all devices. What I suggested
is to bundle all the upstream DTBs for the individual devices into a
single U-Boot binary (CONFIG_MULTI_DTB_FIT) and pick the correct one at
runtime. :)

That should be equivalent to your setup, just more convenient for the
user.

The only open question for me is if we can reliably detect codina-tmo
based on the mach-type ID, I can't find that in the kernel sources I
have.

Thanks,
Stephan