Re: [RFC PATCH v2 09/14] m68k: hp300: Remove hp300_gettimeoffset()

[Geert Uytterhoeven]

Hi Finn,

On Wed, Nov 21, 2018 at 12:13 AM Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx> wrote:
> On atari, the 68901 counts down to 0x01 and raises an interrupt. On mac,
> the 6522 counts down to 0xFFFF then raises an interrupt. No idea about
> amiga (Geert?) -- this has to be handled correctly to get a monotonic
> clocksource. I'll fix this in v3 (where the information is available).

The docs state that the CIA generates on interrupt on underflow, so I
guess that's the same behavior as the 6522 VIA.

Unfortunately the 24-bit ("TOD") counters in the two CIAs run from HSYNC
resp. VSYNC, which depends on the video mode, and thus can't be used
as a monotonic clock source.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds