UART driver progression #1

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opened 2021-05-05 08:38:32 +12:00 by mikedilger · 0 comments

mikedilger commented

2021-05-05 08:38:32 +12:00

(Migrated from github.com)

UART drivers for the 16550 and sifive UART variants will be released in stages with progressive functionality and correctness as follows:

Stage 0: Extremely crude code for kdebug, not even waiting for the write buffer to be ready. Works only in QEMU.
Stage 1: read/write with proper waiting for it to be ready via spinlocks.
Stage 2: Complete functionality, but sans interrupt handling. This needs clocking done first, since setting UART baud rate needs clock information.
Stage 3: Interrupts: Once we start handling interrupts, the UART drivers will change again, dropping the spin loops in favor of interrupt handlers.
Stage 4: Move out of the kernel: Once our microkernel handles processes (after message passing, after capabilities, after a lot of other stuff), the UART code will move to a driver outside of the microkernel.

UART drivers for the 16550 and sifive UART variants will be released in stages with progressive functionality and correctness as follows: - [x] Stage 0: Extremely crude code for kdebug, not even waiting for the write buffer to be ready. Works only in QEMU. - [x] Stage 1: read/write with proper waiting for it to be ready via spinlocks. - [ ] Stage 2: Complete functionality, but sans interrupt handling. This needs clocking done first, since setting UART baud rate needs clock information. - [ ] Stage 3: Interrupts: Once we start handling interrupts, the UART drivers will change again, dropping the spin loops in favor of interrupt handlers. - [ ] Stage 4: Move out of the kernel: Once our microkernel handles processes (after message passing, after capabilities, after a lot of other stuff), the UART code will move to a driver outside of the microkernel.