zlacker

>>todsac+(OP)
With my Librem 5 developer hat on, I'm surprised that a SPI chip matters at all.

The Librem 5 eMMC contains a hidden "partition", which is preferred by the CPU to boot from over the "data partition" where the OS boot loader resides. It should be possible to put Tow-boot into this hidden area, and the OS stored in the data area will have no say. No separate flash chip needed to have an independent boot loader.

I wonder why the PinePhone needs a separate chip for this purpose. Is the CPU unaware of hidden areas on the eMMC?

>>dcz_se+Be
The boot ROM in the RK3399 in the PinePhone Pro has a hardcoded boot order, and doesn't use the special boot partition of the eMMC - it only looks for a bootloader on the data partition at a fixed sector (64).

>>sigmar+Gf
Would it be possible to flash Tow-Boot to that sector and only use the rest of the partition as actual data storage? It seems like it would effectively work the same as having a separate SPI hardware chip on-device, while also restoring distribution independence. The downside is that implementing this might require some special-case support though it could likely be implemented most conveniently by using, e.g. dm-linear, so only configuration changes would be needed, not new kernel code.

>>zozbot+Ok
The issue with that is it's really easily wiped or changed when installing an OS. In the end the SPI hardware did get added and it just works, it's by far the simplest and most reliable solution.