From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756461AbdDRLwE (ORCPT ); Tue, 18 Apr 2017 07:52:04 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:57024 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755965AbdDRLwC (ORCPT ); Tue, 18 Apr 2017 07:52:02 -0400 Date: Tue, 18 Apr 2017 13:51:59 +0200 From: Pavel Machek To: Sakari Ailus Cc: Philipp Zabel , Peter Rosin , Rob Herring , Mark Rutland , Steve Longerbeam , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@pengutronix.de Subject: Re: [RFC 1/2] dt-bindings: add mmio-based syscon mux controller DT bindings Message-ID: <20170418115159.GD14505@amd> References: <20170413154812.19597-1-p.zabel@pengutronix.de> <1492503544.2432.32.camel@pengutronix.de> <20170418100840.GF7456@valkosipuli.retiisi.org.uk> <20170418103453.GC14505@amd> <20170418105540.GH7456@valkosipuli.retiisi.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="gE7i1rD7pdK0Ng3j" Content-Disposition: inline In-Reply-To: <20170418105540.GH7456@valkosipuli.retiisi.org.uk> 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 --gE7i1rD7pdK0Ng3j Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue 2017-04-18 13:55:40, Sakari Ailus wrote: > On Tue, Apr 18, 2017 at 12:34:53PM +0200, Pavel Machek wrote: > > On Tue 2017-04-18 13:08:41, Sakari Ailus wrote: > > > Hi Philipp, > > >=20 > > > On Tue, Apr 18, 2017 at 10:19:04AM +0200, Philipp Zabel wrote: > > > > On Thu, 2017-04-13 at 17:48 +0200, Philipp Zabel wrote: > > > > > This adds device tree binding documentation for mmio-based syscon > > > > > multiplexers controlled by a single bitfield in a syscon register > > > > > range. > > > > >=20 > > > > > Signed-off-by: Philipp Zabel > > > > > --- > > > > > Documentation/devicetree/bindings/mux/mmio-mux.txt | 56 ++++++++= ++++++++++++++ > > > > > 1 file changed, 56 insertions(+) > > > > > create mode 100644 Documentation/devicetree/bindings/mux/mmio-mu= x.txt > > > > >=20 > > > > > diff --git a/Documentation/devicetree/bindings/mux/mmio-mux.txt b= /Documentation/devicetree/bindings/mux/mmio-mux.txt > > > > > new file mode 100644 > > > > > index 0000000000000..11d96f5d98583 > > > > > --- /dev/null > > > > > +++ b/Documentation/devicetree/bindings/mux/mmio-mux.txt > > > > > @@ -0,0 +1,56 @@ > > > > > +MMIO bitfield-based multiplexer controller bindings > > > > > + > > > > > +Define a syscon bitfield to be used to control a multiplexer. Th= e parent > > > > > +device tree node must be a syscon node to provide register acces= s. > > > > > + > > > > > +Required properties: > > > > > +- compatible : "gpio-mux" > > > > > +- reg : register base of the register containing the control bit= field > > > > > +- bit-mask : bitmask of the control bitfield in the control regi= ster > > > > > +- bit-shift : bit offset of the control bitfield in the control = register > > > > > +- #mux-control-cells : <0> > > > > > +* Standard mux-controller bindings as decribed in mux-controller= =2Etxt > > > > > + > > > > > +Optional properties: > > > > > +- idle-state : if present, the state the mux will have when idle= =2E The > > > > > + special state MUX_IDLE_AS_IS is the default. > > > > > + > > > > > +The multiplexer state is defined as the value of the bitfield de= scribed > > > > > +by the reg, bit-mask, and bit-shift properties, accessed through= the parent > > > > > +syscon. > > > > > + > > > > > +Example: > > > > > + > > > > > + syscon { > > > > > + compatible =3D "syscon"; > > > > > + > > > > > + mux: mux-controller@3 { > > > > > + compatible =3D "mmio-mux"; > > > > > + reg =3D <0x3>; > > > > > + bit-mask =3D <0x1>; > > > > > + bit-shift =3D <5>; > > > > > + #mux-control-cells =3D <0>; > > > > > + }; > > > > > + }; > > > > > + > > > > > + video-mux { > > > > > + compatible =3D "video-mux"; > > > > > + mux-controls =3D <&mux>; > > > > > + > > > > > + ports { > > > > > + /* input 0 */ > > > > > + port@0 { > > > > > + reg =3D <0>; > > > > > + }; > > > > > + > > > > > + /* input 1 */ > > > > > + port@1 { > > > > > + reg =3D <1>; > > > > > + }; > > > > > + > > > > > + /* output */ > > > > > + port@2 { > > > > > + reg =3D <2>; > > > > > + }; > > > > > + }; > > > > > + }; > > > >=20 > > > > So Pavel (added to Cc:) suggested to merge these into one node for = the > > > > video mux, as really we are describing a single hardware entity that > > > > happens to be multiplexing multiple video buses into one: > > >=20 > > > Two drivers will be needed in a way or another to disconnect the depe= ndency > > > between the video switch driver and the MUX implementation. Are there= ways > > > to do that cleanly other than having two devices? > >=20 > > Yes. > >=20 > > Device tree describes hardware, not the driver structure. >=20 > I think you you could view the MUX control as a device, too, and that's > separate from the actual video switch. Actually, I believe what matters here is hardware. There's some chip, somewhere, that does the switching, and the device tree should should basically describe that switch. Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --gE7i1rD7pdK0Ng3j Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlj1/d8ACgkQMOfwapXb+vKAJwCfWbgb0nzf1+I9LEgozU1NPDji 0fUAoMRrSSgwTCjlnY28ny2ZKLbncSDQ =wgIl -----END PGP SIGNATURE----- --gE7i1rD7pdK0Ng3j--