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I was just wrapping my head around on how do they even run linux on the RISC-V microcontroller they use. Turns out there is a separate ARM for application processor.

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Yeah. As I'm sure you're aware, you can get Linux capable RV. I mean you can build mmu-less as well but there's plenty of I think it's M extension cores out there. This isn't that. This is a design that happens to use at least one RV core and happens to be capable of hosting a modem card. It's not a RISC-V mobile phone.

From what I can tell, the RISC-V processor handles all of the phone functionality in a way that's almost entirely decoupled from the app-module/smartphone features. The phone part has its own firmware and drives the screen separately from the app-module. They added a green indicator light to show when the RISC-V "core" is using the screen vs when the app-module is.

The graphics processor is probably just for when the RISC-V core takes over the screen, as well.

What's the purpose though? You can put your own code on the app processor too. I don't know Android kernel dev but presumably with aosp you can do whatever the RV core does either in the A class core or using one of the many SoMs with built-in M class cores.

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