[PATCH v3 2/2] ARM: am335x: Changed timer
s.hauer at pengutronix.de
Sun Jul 19 22:36:05 PDT 2015
On Fri, Jul 17, 2015 at 04:57:48PM +0200, Jan Lübbe wrote:
> On Fr, 2015-07-17 at 15:39 +0200, Daniel Schultz wrote:
> > The dmtimer0 is too inaccurate to be used for measurements.
> > We switch to the more accurate dmtimer2.
> Ah, OK, after looking at the TRM again, the real reason for the
> inaccuracy seems to be that the 32KiHz for dmtimer0 is *not* derived
> from the RTC crystal, but from an internal RC oscillator.
> The kernel uses dmtimer1 for the clocksource by switching it to the
> M_OSC in the PRCM.
> The dmtimer2 is used for clockevents and runs from M_OSC by default.
> While we could set the dmtimer1 source to M_OSC in the clock setup, it
> seems simpler to just use dmtimer2.
> The commit message should explain the reasoning behind the switch.
Changed the commit message while applying to:
The 32KHz from dmtimer0 is derived from a SoC internal RC oscillator
which is quite inaccurate. Switch to dmtimer2 which is driven from
the high frequency oscillator clock.
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