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.