From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Jarzmik Subject: Re: [PATCH v2] video: fbdev: add Marvell PXA framebuffer binding Date: Thu, 08 Oct 2015 21:15:00 +0200 Message-ID: <87lhbd9npn.fsf@belgarion.home> References: <1443954683-13126-1-git-send-email-robert.jarzmik@free.fr> <87y4ffaj3m.fsf@belgarion.home> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: (Rob Herring's message of "Thu, 8 Oct 2015 08:30:36 -0500") Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring , Philipp Zabel Cc: Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Jean-Christophe Plagniol-Villard , Tomi Valkeinen , "linux-fbdev@vger.kernel.org" List-Id: devicetree@vger.kernel.org Rob Herring writes: >> The pxafb driver acts today on the subset of registers which are the same across >> all pxaXXX variants. This is what made me think only one compatible property was >> required. >> >> If I'm wrong, I could add "marvell,pxa3xx-lcdc", is that what you think I should >> do ? > > I would prefer specific compatibles (e.g. marvell,pxa270-lcdc) in > addition to a generic one. You never know when a specific chip will > have some quirk even though "the IP is the same". Okay. >> And then, when a board maintainer will create a devicetree description, he will >> write something like : >> compatible = "toshiba,ltm0305a776"; >> compatible = "marvell,pxa2xx-panel"; > > Drop this compatible. > >> lcd-type = "color-tft"; >> ... >> >> If that's the case, I wonder how to "enforce" that a panel used with >> marvell,pxa2xx-lcdc (through the of_graph 'port' node) be compatible with >> marvell,pxa2xx-panel ? > > I'm not sure what you mean. Putting the panel into the dts ensures > that. The FB driver may check for toshiba,ltm0305a776 or a list of > panels. However, a DRM driver would probably not check that. > > Rob What I mean is that the LDLC controller _must_ be programmmed with the correct panel type, ie. one register of the LDLC should be set according to this type. The type is a hardware property of the panel, and yet it is absolutely mandatory to have it set in the panel. What I mean is : what is the good way to enforce that this property is set somewhere in the devicetree description ? Philipp adviced for it to be transfered to the ldlc description (ie. marvell,pxa2xx-ldlc), while I was thinking of having it in a panel description. Cheers. -- Robert