From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Reichel Subject: Re: [PATCH RFC 2/3] power: mxs_power: add driver for mxs power subsystem Date: Wed, 28 Jan 2015 23:59:38 +0100 Message-ID: <20150128225937.GA12749@earth.universe> References: <1416514477-19190-1-git-send-email-stefan.wahren@i2se.com> <1416514477-19190-3-git-send-email-stefan.wahren@i2se.com> <20150121230148.GJ13715@earth.universe> <54C0AFE4.3020701@i2se.com> <20150125150431.GE2719@earth.universe> <1719204322.245040.1422301605670.JavaMail.open-xchange@oxbaltgw03.schlund.de> <20150127001629.GP21293@sirena.org.uk> <1954124242.301697.1422383709733.JavaMail.open-xchange@oxbaltgw09.schlund.de> <20150127194346.GN21293@sirena.org.uk> <443299280.47516.1422483725178.JavaMail.open-xchange@oxbaltgw03.schlund.de> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1666247968187865887==" Return-path: In-Reply-To: <443299280.47516.1422483725178.JavaMail.open-xchange@oxbaltgw03.schlund.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Stefan Wahren Cc: Mark Rutland , Marek Vasut , Pawel Moll , Ian Campbell , Dmitry Eremin-Solenikov , David Woodhouse , Mark Brown , linux-pm@vger.kernel.org, Liam Girdwood , devicetree@vger.kernel.org, Rob Herring , Sascha Hauer , Kumar Gala , Shawn Guo , Fabio Estevam , "linux-arm-kernel@lists.infradead.org" List-Id: devicetree@vger.kernel.org --===============1666247968187865887== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="wac7ysb48OaltWcw" Content-Disposition: inline --wac7ysb48OaltWcw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Wed, Jan 28, 2015 at 11:22:05PM +0100, Stefan Wahren wrote: > > Mark Brown hat am 27. Januar 2015 um 20:43 geschri= eben: > > On Tue, Jan 27, 2015 at 07:35:09PM +0100, Stefan Wahren wrote: > > > > Mark Brown hat am 27. Januar 2015 um 01:16 > > > > geschrieben: > > > > > > > okay i understand. But doesn't it need a extra driver to set the > > > > > switching > > > > > frequency because of the new compatible string? > > > > > > I don't understand this bit at all, sorry. > > > > > Sebastian suggested a new sub-node in the devicetree: > > > > > powerpll { > > > compatible =3D "fsl,imx28-power-pll" > > > #clock-cells =3D <0>; > > > clock-frequency =3D <12345>; > > > } > > > > > and i think that the new compatible string needs a separate driver to= take > > > care > > > of the switching frequency. > > > > I can see that this has been suggested, what I can't understand is why > > we would wish to do this but I am missing some context here which may > > make it all perfectly clear. >=20 > The relevant register DC-DC Miscellaneous Register (HW_POWER_MISC) is des= cribed > in chapter 11.12.10 of the reference manual [1]. > > [1] - http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf Having a look at the datasheet my suggestion for the sub-node doesn't make sense. I missunderstood how the hardware architecture looks like, sorry for the noise :( > changing the switching frequency is not a common feature for this IC. In = most > cases the clock for the DC-DC switching frequency runs at 24 MHz (ref_xta= l). > Unfortunatelly this could cause interferences for example in UHF band. So > switching to ref_pll and changing clock divider is a option to avoid such > interferences without changing hardware. > > I decided to implement it as a module parameter, because i see it's a > configuration option. I think its best to use a DT property then. That way it can be set appropiatly for boards known to use a band, which could have interference problems. So just add a simple property (without a subnode). If I understand Mark correctly, there's a high chance more drivers will need to describe the switching frequency, so I suggest to use a vendor independent property name: switching-frequency =3D <12345>; -- Sebastian --wac7ysb48OaltWcw Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJUyWnXAAoJENju1/PIO/qaQ9YP/j8+hSDHXuHvx895UVtcA3Qx Cv2JE3LZchHgubIt/VL9yB65Qz8HxwafsG/94N9Ry3ZTnBCMGZiBtcBY3TH4jkcC qunliXVgu5IRYav5diQIgZjmuh0nsWelAkefmbWclDmdtPX5qX4LtkjWQ9ZxPjF6 2lnC0wf8WYra5QKAOxC1MhzcuuizF8vrshagjT08m7z+YlX9Pz+SXvVOOi/Bi+3l g2P8SBrgbUq7uRXDbMHG+WoTPC0rkjqrIrvkVW8T0pUlpjyRKIWPZ9bVqCeQ8RJT iwvTlTPKl6qjSLmedvdaLmMiBLhngY6nbbF0J48PGK57/0P6PnUn0szsmG5w4/bh T58U2mCmHWD0fUMCUbB6JrgN4tzkWRQ6x7Py7hWzZQ41htihUXWFvU8vYt0zlyQE /cmGD5C5ep0HUUEJYpZDntpvY6VsuYDUM6BiaI1qgqEQc0bU8UoVMzavkrKwbi3w l7tWdYetlZC233IynmmK6kRhQ88O9cENVidwqmKiWWKHRm6oofkHUBlbncoLnnTu svPAbLD3HCVnfQ17khG5PwNXhIFd2TDnQKNZvVNrSsesBpuujASKWoI1PNawqYEJ yAnOVVYRMRaxe/2TeRYEjUWU3OaG0ZwAosKnpDVcfeUWsZ7J+46xYA6u5tQADaup w6JDCBL5LNE6ZregTUcB =vbXr -----END PGP SIGNATURE----- --wac7ysb48OaltWcw-- --===============1666247968187865887== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============1666247968187865887==--