From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751256AbcEDOKF (ORCPT ); Wed, 4 May 2016 10:10:05 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:34822 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750779AbcEDOKC (ORCPT ); Wed, 4 May 2016 10:10:02 -0400 MIME-Version: 1.0 In-Reply-To: <5728E0BC.3080509@ti.com> References: <20160427171658.GA5995@atomide.com> <1462209123-7332-1-git-send-email-Linux.HWI@garmin.com> <1462209123-7332-3-git-send-email-Linux.HWI@garmin.com> <57285E66.2000708@ti.com> <5728A81F.4050906@garmin.com> <20160503164323.GN5995@atomide.com> <5728E0BC.3080509@ti.com> From: Matthijs van Duin Date: Wed, 4 May 2016 16:09:40 +0200 Message-ID: Subject: Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency To: Tero Kristo Cc: Tony Lindgren , "J.D. Schroeder" , lkml , bcousson@baylibre.com, robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, Russell King - ARM Linux , "linux-omap@vger.kernel.org" , devicetree , "linux-arm-kernel@lists.infradead.org" , jay.schroeder@garmin.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3 May 2016 at 18:43, Tony Lindgren wrote: > Does a fixed divider calculation of input * (32768 / 27e6) make sense > here too as pointed out earlier by Matthijs for the ti81xx? That was an actual fractional divider, i.e. the output clock would be exactly that ratio of the input clock, which would therefore yield 32768 Hz if the default crystal is used for the main osc. It makes no sense to use it to describe a wobbly RC osc. On 3 May 2016 at 19:32, Tero Kristo wrote: > Also, as it is security related, this is kind of sensitive area to discuss publicly. Don't be silly. The only sense in which this clock is "security related" is because it's used for the secure watchdog, and the reason to use it despite its inaccuracy is completely obvious: an internal rc osc can't be easily manipulated by an external attacker. I see no reason to act all cloak-and-dagger about this. (This seems to be a general theme to conceal "security related" things from public documentation. If I were an HS customer I'd actually be concerned about such behaviour since it would seem to indicate a lack of confidence in one's security architecture.) Matthijs