On Mon, Sep 18, 2017 at 03:41:56PM +0300, Artturi Alm wrote:
> On Mon, Sep 18, 2017 at 11:19:09AM +0100, Stuart Henderson wrote:
> > On 2017/09/18 04:28, Artturi Alm wrote:
> > > Do i really need to reference datasheets, or would someone explain to me
> > > the value of this MSB robbing?
> >
> > I think, if you're proposing a change, you should explain why that
> > change should be made, rather than asking others to defend the current
> > situation..
> >
>
> guess i wasn't clear enough. of the 3 timers two are 64bit timers, of them
> agtimer doesn't even support reading just 32bit, nor any of them do just
> 31bits as claimed by the timercounter mask.
> so all of them act opposite to what's written in sys/timetc.h, the last bit
> won't be constant with these.
>
> amptimer's low register does have full 32bits, if it didn't, i doubt this
> function could exist:
> /sys/arch/arm/cortex/amptimer.c:
> 128 uint64_t
> 129 amptimer_readcnt64(struct amptimer_softc *sc)
> 130 {
> 131 uint32_t high0, high1, low;
> 132 bus_space_tag_t iot = sc->sc_iot;
> 133 bus_space_handle_t ioh = sc->sc_ioh;
> 134
> 135 do {
> 136 high0 = bus_space_read_4(iot, ioh, GTIMER_CNT_HIGH);
> 137 low = bus_space_read_4(iot, ioh, GTIMER_CNT_LOW);
> 138 high1 = bus_space_read_4(iot, ioh, GTIMER_CNT_HIGH);
> 139 } while (high0 != high1);
> 140
> 141 return ((((uint64_t)high1) << 32) | low);
> 142 }
>
> if you google for "swpu223g" you'll find omap3430 technical reference manual
> pdf, in it you can find the description of gptimer's TCRR register, at
> page 2600, also it _will_ count beyond 0x7fffffff.
>
> you can find reference to gptimer(missed replace) from amptimer.c, i guess
> amptimer was where agtimer got it from, so maybe just an bad copy-paste.
>
i meant to write "(missed replace?)" above, as i'm not sure,
but now i think i know who i should have cc'ed initially.
i'm guessing the chain has gone something like this:
macppc||socppc->beagle's gptimer->panda's amptimer->agtimer->arm64 agtimer
drahn@, would you help me out a bit here? do you know/remember about
these enough, to ok what i've suggested(+same for arm64 agtimer) to anyone
who could pick this up?
-Artturi
> -Artturi
