Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752697AbbHCJXc (ORCPT ); Mon, 3 Aug 2015 05:23:32 -0400 Received: from down.free-electrons.com ([37.187.137.238]:58001 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752531AbbHCJX2 (ORCPT ); Mon, 3 Aug 2015 05:23:28 -0400 Date: Mon, 3 Aug 2015 11:23:25 +0200 From: Maxime Ripard To: Timo Sigurdsson Cc: julian.calaby@gmail.com, robh+dt@kernel.org, pawel.moll@arm.com, mark.rutland@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, linux@arm.linux.org.uk, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com, wens@csie.org Subject: Re: [linux-sunxi] [PATCH] ARM: dts: sunxi: Raise minimum CPU voltage for sun7i-a20 to a level all boards can supply Message-ID: <20150803092325.GA2564@lukather> References: <1438543386-7253-1-git-send-email-public_timo.s@silentcreek.de> <20150803083751.1BCF56C80391@dd34104.kasserver.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="gQ68Z+YvpGk0qVJK" Content-Disposition: inline In-Reply-To: <20150803083751.1BCF56C80391@dd34104.kasserver.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2595 Lines: 71 --gQ68Z+YvpGk0qVJK Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Aug 03, 2015 at 10:37:51AM +0200, Timo Sigurdsson wrote: > Hi Julian, >=20 > Julian Calaby schrieb am 03.08.2015 01:35: > >> sun7i-a20.dtsi contains an cpufreq operating point at 0.9 volts. Most = A20 > >> boards > >> (or all?), however, do not allow the voltage to go below 1.0V. Thus, r= aise the > >> voltage for the lowest operating point to 1.0V so all boards can actua= lly use > >> it. > >=20 > > Surely it wouldn't be added here if some could supply 0.9v. >=20 > Maybe. I just know some boards don't (e.g. Cubieboard 2, Cubietruck, Bana= naPi) > and don't know of any that does. But that's not my point. I think that a = common > minimum operating point, defined on the SOC level, should be defined in a= way > that works on all boards. All of them can supply it. The DCDC2 regulator they use for the CPU can go as low as 0.7V. The question is whether the CPU itself can work at such a low voltage. And the operating limits for the CPU is documented to be 1V - 1.4V. Anything else is either over or underclocking, which might or might not work on individual SoCs. So it's not something that we're going to support. Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --gQ68Z+YvpGk0qVJK Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJVvzMNAAoJEBx+YmzsjxAgdFQP/RCMBNqd7w6tmkJ/b4Y0o8iB rIiXNN+1DTgmLG5cZdjuvNtc9tfaYQ+KFEh8oLiAIr3gP2GFe68BzTGmq9x0oqcQ iuXjZniL3XYVZuuOj/mTbtjRbXIUubfxnltZTaZ94uPNlYN5oU1KNF2stP3BsI5w T9wQ4CEylBMCrv5eJ98mVgCNz46FxyoRlsozrRhxnkxInhcx3y6ixNA9wxdxZTNW is5u653UfWEPXdRZ4b7QiiA+20i1tIql+qXfqFySvTExmgwpCecshhnq0xJViaPk zd2PyAKz3rRlj3dDe31orA/zC9RUT64TaNtAzuhTSHle4l4LIhU0H5xnwsYLWvLT +QFpXqj33PS5wYCSyYwL7rc1glatHini0asT/pIQUZRT++tIwxXvDwtxht+BkfAV pqGtKqAeo44b7aDESUrzSuP9YfKVfJ6KSqPdQnPfLXYFqct/nYNT4znSfwRjhLhp WCBJMXG1/0nQG5lg+TtqFRCajlRuFabVFUBccN1rBXt0mUhaVCJX4IUVUU+LB1Uz 3CAAss2QZ/7P7DtyqoB2aUrjW4hKKI9rSAaqA3xiesr+WZb0+SarNPxDiu6MSB8M Sw7XqvBaGIELia0mSxKfI2J9/0Xb8d37XtXtFW1FsbL9eF7CdUSnIK3xjxn/yedN HrCVMyXRVe6OZZS2+o0X =8x79 -----END PGP SIGNATURE----- --gQ68Z+YvpGk0qVJK-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/