Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752352AbdF3MMW (ORCPT ); Fri, 30 Jun 2017 08:12:22 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:50652 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752020AbdF3MKq (ORCPT ); Fri, 30 Jun 2017 08:10:46 -0400 Date: Fri, 30 Jun 2017 13:10:26 +0100 From: Mark Brown To: Viresh Kumar Cc: Chen-Yu Tsai , "Enrico Weigelt, metux IT consult" , Rafael Wysocki , Vincent Guittot , Rob Herring , Greg Kroah-Hartman , Stephen Boyd , linux-kernel , rnayak@codeaurora.org, Shiraz Hashim , linux-arm-kernel Message-ID: <20170630121026.azppihjqls5i6bbr@sirena.org.uk> References: <1522ae7b-fd5b-5403-62bf-b0140e116d65@gr13.net> <20170630031648.GR29665@vireshk-i7> <20170630035533.GV29665@vireshk-i7> <20170630041211.GX29665@vireshk-i7> <20170630051203.GY29665@vireshk-i7> <20170630084330.GB29665@vireshk-i7> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zdf7pqnsen64jbvr" Content-Disposition: inline In-Reply-To: <20170630084330.GB29665@vireshk-i7> X-Cookie: 667: User-Agent: NeoMutt/20170609 (1.8.3) X-SA-Exim-Connect-IP: 176.12.107.140 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [RFC 0/5] drivers: Add boot constraints core X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: No (on mezzanine.sirena.org.uk); Unknown failure Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2226 Lines: 62 --zdf7pqnsen64jbvr Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jun 30, 2017 at 02:13:30PM +0530, Viresh Kumar wrote: > On 30-06-17, 14:36, Chen-Yu Tsai wrote: > Operable ranges of the regulator: 1.8 - 3.0 V > Range required by LCD: 2.0 - 3.0 V > Range required by DMA: 1.8 - 2.5 V > Here DMA can't work with regulator voltages > 2.5 V, but regulator can > go max to 3.0 V. Of course if the DMA driver has done > regulator_set_voltage(), then we will be within 2.5 V range. But that > doesn't force us to have regulator-max-microvolt set to 2.5 V. > And so the DT node shall have this: > regulator-min-microvolt =3D <1800000>; > regulator-max-microvolt =3D <3000000>; > Isn't it ? If the DMA can't tolerate more than 2.5V then why would the constraints allow the voltage to float that far? Similarly on the low end? Please remember that devices shouldn't be managing their voltages unless they are actively changing them at runtime, simply setting them at startup is the job of the constraints. I would be very surprised to see a DMA controller doing anything like DVFS. >=20 > > This might be unrelated, but I think it is a similar problem. When a > > clk rate change is propagated up the clk tree, any affected sibling > > clks aren't automatically readjusted, i.e. try to keep roughly the > > same output clk rate by adjusting its own dividers. This might be > > one side of the problem you are trying to solve. >=20 > I am not sure how this problem can be solved with what this set is > proposing. :( >=20 > --=20 > viresh --zdf7pqnsen64jbvr Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAllWP7EACgkQJNaLcl1U h9Dcsgf/RsJqnpOhKXV+DnWEn/efHGXMittexi7idFNovRH4h+x2APy+g3iOhfDC xKmNi0TUVdEbosZ0gLdl0XAwenOD1bHCvWMNhWeL3NMSi7FGaAmdXBc6M2ETUooS yztK+amkmwqDI+vQ418S1+K3gF0iSbuPGEmYde5vCONojZ1YH3oOK+gWl2/R5WDA +A/VjgecJBR8OfhfPHN0Yz2zRwUqZrk6EIKpCwCt0QVYkbbT4v7sKOQysU+8iFYb zZZJdcd6MtoVPmyG1GuU22JJt8GrNY3aYIMI2FRZIopMcMGS+nkMmoBgyWgHgNDP s103BP0hnprOP+zy7DDw4cC5pC9ErA== =Bc7r -----END PGP SIGNATURE----- --zdf7pqnsen64jbvr--