[TUHS] Of /dev/tty8
segaloco via TUHS
tuhs at tuhs.org
Tue Mar 19 06:22:15 AEST 2024
On Monday, March 18th, 2024 at 1:08 PM, Ron Natalie <ron at ronnatalie.com> wrote:
> The other problem with the DZ is it was one interrupt per character if I
> recall.
> Thte DH you could get multiple (output) characters per interrupt.
> Greatly decreased the load on the system.
>
> I do remember the KL kernel prints were not interrupt driven so the
> system pretty much froze while the kernel printfs were being output.
> There was a comment on the code saying this was “Not for idle chit
> chat.”
Yep, synchronous code that writes a character at a time to the transmit register then spins on a status bit awaiting transmit complete, or something like that. I adapted the V6 kernel printf to a RISC-V board I was working on the past year to have a trustworthy print mechanism, only caveat being the transmitter status register was a dirty filthy liar and wouldn't flip the bit on transmit, so just had to put a delay, which it turns out all of the BSDs currently also do for Ti 16550-family UARTs as well.
- Matt G.
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