From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: [RFC] OPP: Redefine bindings to overcome shortcomings Date: Thu, 4 Dec 2014 17:18:49 +0000 Message-ID: <20141204171849.GX7712@sirena.org.uk> References: <52c403454c3b8fc201abe7ac74cf657638479311.1417691389.git.viresh.kumar@linaro.org> <1417692868.9037.4.camel@pengutronix.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="JBABWuYasNt1mk88" Return-path: Content-Disposition: inline In-Reply-To: <1417692868.9037.4.camel@pengutronix.de> Sender: linux-pm-owner@vger.kernel.org To: Lucas Stach Cc: Viresh Kumar , nm@ti.com, rob.herring@linaro.org, kesavan.abhilash@gmail.com, linaro-kernel@lists.linaro.org, catalin.marinas@arm.com, linux-pm@vger.kernel.org, sboyd@codeaurora.org, santosh.shilimkar@oracle.com, Rafael Wysocki , olof@lixom.net, devicetree@vger.kernel.org, mike.turquette@linaro.org, Sudeep.Holla@arm.com, grant.likely@linaro.org, thomas.petazzoni@free-electrons.com, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org --JBABWuYasNt1mk88 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Dec 04, 2014 at 12:34:28PM +0100, Lucas Stach wrote: > Am Donnerstag, den 04.12.2014, 16:44 +0530 schrieb Viresh Kumar: > > + - voltage-tolerance: Specify the CPU voltage tolerance in percentage. > This is extremely ill defined. It doesn't say in which direction the > tolerance is to be applied. Can you go below or above the OPP specified > voltage? For now everyone just assumes that it has to work both ways. > Also with this binding the tolerance is applied for all OPPs, where is > very much depends on the individual OPP. Almost all specifications for voltages are done as either min/typ/max or +/- a target voltage. > If you are going to redefine OPPs anyway I would really like to see this > property die and rather have a min/max voltage per OPP. That way you can > properly express the OPP constraints. Most OPPs will likely allow a much > higher voltage than their minimal specified one, except when you go over > thermal limits with a high clock/voltage combination. If you've got a minimum and maximum you also need to specify a target, generally it's going to be better to go for the target voltage which may not be the midpoint and is unlikely to be one of the bounds. I do think it's sensible to have the option of doing both to more closely match datasheets. > > + - clock-latency: Specify the possible maximum transition latency for clock, > > + in unit of nanoseconds. > Why do we need this? This is property of the clock. We should be able to > handle this completely internally in the kernel. I don't know if the > clock API has something like this right now, but it should be a trivial > addition. Or have it be part of the clock binding at any rate. --JBABWuYasNt1mk88 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBAgAGBQJUgJd4AAoJECTWi3JdVIfQO2cH/A4xkox0tV1u0JGW0NZZ64CB iG9m41Xnvtdio2GQH7wyCZ6Q+w3Uz6JdKHq/LPG/EqVNzop7aa5F4v+MFD5pyAlx iTauzhvWV+FtrAek6SkOm/f96J5K2edYHVPygAmsXbjuID2u4dJ4TjdUB+tvT+vq DnrvlZZJkhtG6TgHekKBhGe1lyoDJagC4T6ZmIhewtBSZvnY8bRR7U2eQFqzz+lT If5B55ybdhHOvdDQ50DKc1F/4AYZzX0m79eK4YkYV1NxRVnbbzbzhKAzpI0HfZg6 PgbYIN1PJoGvvOD4UB9u8MxS2dvgCuFx9zXJyEoXadxS6WEDW9BaArXlQLPGsM8= =Yk1q -----END PGP SIGNATURE----- --JBABWuYasNt1mk88--