From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZH3kZ-00079Y-4N for barebox@lists.infradead.org; Mon, 20 Jul 2015 05:36:30 +0000 Date: Mon, 20 Jul 2015 07:36:05 +0200 From: Sascha Hauer Message-ID: <20150720053605.GT18700@pengutronix.de> References: <1437140350-14352-1-git-send-email-d.schultz@phytec.de> <1437145068.3498.117.camel@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1437145068.3498.117.camel@pengutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: quoted-printable Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH v3 2/2] ARM: am335x: Changed timer To: Jan =?iso-8859-15?Q?L=FCbbe?= Cc: barebox@lists.infradead.org, Daniel Schultz On Fri, Jul 17, 2015 at 04:57:48PM +0200, Jan L=FCbbe 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. Sascha -- = Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox