From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3700CC6379F for ; Tue, 21 Feb 2023 12:48:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230202AbjBUMso (ORCPT ); Tue, 21 Feb 2023 07:48:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47266 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233489AbjBUMsk (ORCPT ); Tue, 21 Feb 2023 07:48:40 -0500 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C895C3595; Tue, 21 Feb 2023 04:48:22 -0800 (PST) Received: from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi [213.243.189.158]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 140E2519; Tue, 21 Feb 2023 13:48:21 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1676983701; bh=92SGzzXXowAiCNzfDsVMTyZZXu8ho+adWw8J/+Bd3OA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TqtbnfQ96LQYY5FGsxqNrA7Hf75DXhBIEy6+afsrA0UzoPzYNs5oed4CHs1Wx37Nj YeeIbjp6IQkeGW04rIRWPmPoNgVUtAVdDqypaM7rVjYjJWZKsMqwy7qE+vMREylPjP 8XUpHhc7oyZdzjksNMejXvam2iJ9xNAAoG3AZxDM= Date: Tue, 21 Feb 2023 14:48:19 +0200 From: Laurent Pinchart To: Sakari Ailus Cc: linux-media@vger.kernel.org, Jacopo Mondi , Rob Herring , devicetree@vger.kernel.org Subject: Re: [PATCH v2 1/2] media: dt-bindings: media: i2c: Add MT9M114 camera sensor binding Message-ID: References: <20220207012055.15158-1-laurent.pinchart@ideasonboard.com> <20220207012055.15158-2-laurent.pinchart@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi Sakari, On Tue, Feb 21, 2023 at 02:42:31PM +0200, Sakari Ailus wrote: > On Tue, Feb 21, 2023 at 01:52:46AM +0200, Laurent Pinchart wrote: > > > > > > > + properties: > > > > > > > + bus-type: > > > > > > > + enum: [4, 5, 6] > > > > > > > > > > > > With bus-type 5, shouldn't you have the parallel interface sync signal > > > > > > polarity properties? Possibly also others if the hardware supports them. > > > > > > > > > > As far as I can tell, the hardware has fixed polarities for all signals. > > > > > Both hsync and vsync (called LINE_VALID and FRAME_VALID here) are active > > > > > high. > > > > > > > > Right, then you won't need these. > > > > > > > > What about the link-frequencies property? > > > > > > That's something I've meant to ask, should the link-frequencies property > > > be specified for parallel buses too, or only CSI-2 ? > > > > Any feedback on this ? > > Yes. > > It very likely matters there as well but probably less so than on CSI-2. > > link-frequencies isn't specific to CSI-2 either. > > > > We also need to document how a DT writer should select the link > > > frequencies. The process is complicated, saying that the property is > > > required without explaining how the values can be computed (EMC > > > constraints aside, just from a functional point of view) isn't nice. If > > > you explain this to me, I can put it in a patch :-) > > > > Or on this ? :-) > > Generally the hardware people will tell you this when it matters. :-) But > on a development board you can probably have anything the hardware > supports. > > I guess we could add a few words on this to e.g. > Documentation/driver-api/media/camera-sensor.rst . Please :-) When the sensor driver supports multiple link frequencies, and in particular a continuous range of frequencies, I want a document I can point people to precisely answer the "I have no idea about those stuff, what value do I put in my device tree?" question. It should include a clear procedure to calculate a value, not just a generic statement along the lines of "pick a value that is suitable for you". > Most drivers will support a few frequencies only and sometimes the vendor, > due to someone needing it, provides another configuration with a different > frequency. Many sensors also have datasheets that are precise enough to > calculate this yourself. -- Regards, Laurent Pinchart