On Sat, Nov 16, 2019 at 12:46 PM Kars de Jong <jongk@xxxxxxxxxxxxxx> wrote:
> The msm6242_set()/msm6242_clear() functions are used when writing to Control
> Register D to set or clear the HOLD bit when reading the current time from
> the RTC.
>
> Doing this with a read-modify-write cycle will potentially clear an
> interrupt condition which occurs between the read and the write.
>
> The datasheet states the following about this:
>
> When writing the HOLD or 30 second adjust bits of register D, it is
> necessary to write the IRQ FLAG bit to a "1".
>
> Since the only other bits in the register are the 30 second adjust bit
> (which is not used) and the BUSY bit (which is read-only), the
> read-modify-write cycle can be replaced by a simple write with the IRQ FLAG
> bit set to 1 and the other bits (except HOLD) set to 0.
>
> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Tested-by: Kars de Jong <jongk@xxxxxxxxxxxxxx>
> Signed-off-by: Kars de Jong <jongk@xxxxxxxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
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
