From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.free-electrons.com ([62.4.15.54]:44037 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757027AbdHYOow (ORCPT ); Fri, 25 Aug 2017 10:44:52 -0400 Date: Fri, 25 Aug 2017 16:44:40 +0200 From: Maxime Ripard To: Laurent Pinchart Cc: Cyprian Wronka , Mauro Carvalho Chehab , Mark Rutland , Rob Herring , "linux-media@vger.kernel.org" , "devicetree@vger.kernel.org" , Neil Webb , Richard Sproul , Alan Douglas , Steve Creaney , Thomas Petazzoni , Boris Brezillon , Niklas =?iso-8859-1?Q?S=F6derlund?= , Hans Verkuil , Sakari Ailus Subject: Re: [PATCH v2 1/2] dt-bindings: media: Add Cadence MIPI-CSI2 RX Device Tree bindings Message-ID: <20170825144440.beettgwsynics3hs@flea.lan> References: <20170720092302.2982-1-maxime.ripard@free-electrons.com> <6400552.TlCMAsqn3H@avalon> <2518768.foDtbh9bhx@avalon> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kg6e2lxjy7lvnzvb" Content-Disposition: inline In-Reply-To: <2518768.foDtbh9bhx@avalon> Sender: linux-media-owner@vger.kernel.org List-ID: --kg6e2lxjy7lvnzvb Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Laurent, On Wed, Aug 23, 2017 at 12:03:32AM +0300, Laurent Pinchart wrote: > >>>>> + - phys: phandle to the external D-PHY > >>>>> + - phy-names: must contain dphy, if the implementation uses an > >>>>> + external D-PHY > >>>>=20 > >>>> I would move the last two properties in an optional category as > >>>> they're effectively optional. I think you should also explain a bit = more > >>>> clearly that the phys property must not be present if the phy-names > >>>> property is not present. > >>>=20 > >>> It's not really optional. The IP has a configuration register that > >>> allows you to see if it's been synthesized with or without a PHY. If > >>> the right bit is set, that property will be mandatory, if not, it's > >>> useless. > >>=20 > >> Just to confirm, the PHY is a separate IP core, right ? Is the CSI-2 > >> receiver input interface different when used with a PHY and when used > >> without one ? Could a third-party PHY be used as well ? If so, would t= he > >> PHY synthesis bit be set or not ? > >=20 > > The PHY (in our case a D-PHY) is a separate entity, it can be from a 3rd > > party as the IP interface is standard, the SoC integrator would set the= bit > > accordingly based on whether any PHY is present or not. There is also an > > option of routing digital output from a CSI-TX to a CSI-RX and in such = case > > a PHY would not need to be used (as in the case of our current platform= ).=20 >=20 > OK, thank you for the clarification.=20 >=20 > Maxime mentioned that a bit can be read from a register to notify whether= a=20 > PHY has been synthesized or not. Does it influence the CSI-2 RX input=20 > interface at all, or is the CSI-2 RX IP core synthesized the same way=20 > regardless of whether a PHY is present or not ? So we got an answer to this, and the physical interface remains the same. However, the PHY bit is set only when there's an internal D-PHY, which means we have basically three cases: - No D-PHY at all, D-PHY presence bit not set - Internal D-PHY, D-PHY presence bit set - External D-PHY, D-PHY presence bit not set I guess that solves our discussion about whether the phys property should be marked optional or not. It should indeed be optional, and when it's not there, the D-PHY presence bit will tell whether we have to program the internal D-PHY or not. Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com --kg6e2lxjy7lvnzvb Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIcBAEBAgAGBQJZoDfYAAoJEBx+YmzsjxAg/BUP/AkINzgm7mIxywWlSsy+nVdL 4evQiODK2NKY3AhosavTKDbwCOSOkAWJb8lO0knhWQ/7DtEw81V0ZxMrSu0faVZg lpiTuXCKwwWK9up+Zc4V1xgKe9huyYcOdixk4EPRDYvsdJwmXa9Bv1krZb/i/6Oh GDNDbVG1dPVB+3pX92wMINFM2cZDMDjLCSfgWTYyE893FvF/9U/ZX3vZr+m9ECJR SSLQQjQBdFPZ3I81ngIjByhhQ7BwmEd8R5gCIwUPlwoCVQ4dHiYfPgVI48GH+HqJ WTblG6jADnfjdBO5gvGBRsm9FKxiltcCMATno8CPwL974DkrMGDKd+iSuu2GwZZE HYlGgAecKKot7wFcVw6GblA/YbmKulBuMPpsbXbVLuqNwvn+zP5uwpUfrMJyYDcW qGiXBojOE9nLnd48gZHwcBs4cTFiGc8NDP4+SW6WHjOrnmFUeBC++hYGZZjUpJ4J h93MzKRNyL+dEGurmKfh3mJEauHvcmoFV5G2i9vKTuFRRdScKqLxxUwZfgksxQDI Q4c63daFHpfASNZipG4bhE0vXyrxT2EZ4u1x742fE1OEm1+khuOH1oD3stP/BsMN ah0dpehrlpDecQo6A9blMHGEB6yNfJdvK8J8piKr0wkzGWe6beL3Dyzft2VFJpuR UeRSMLRw1DHgigcqB8Gj =iIfR -----END PGP SIGNATURE----- --kg6e2lxjy7lvnzvb--