From: "Jan Lübbe" <jlu@pengutronix.de>
To: Daniel Schultz <d.schultz@phytec.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH v3 2/2] ARM: am335x: Changed timer
Date: Fri, 17 Jul 2015 16:57:48 +0200 [thread overview]
Message-ID: <1437145068.3498.117.camel@pengutronix.de> (raw)
In-Reply-To: <1437140350-14352-1-git-send-email-d.schultz@phytec.de>
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.
Regards,
Jan
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next prev parent reply other threads:[~2015-07-17 14:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-17 13:39 Daniel Schultz
2015-07-17 14:57 ` Jan Lübbe [this message]
2015-07-20 5:36 ` Sascha Hauer
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