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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47E56C10F27 for ; Mon, 9 Mar 2020 20:22:27 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1F56624671 for ; Mon, 9 Mar 2020 20:22:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="nBLOCSK1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F56624671 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=collabora.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=8e6seghZUx7ZP1/9qKztAuR7AWIewBPYqHqFuRE6llg=; b=nBLOCSK1bWc/63 rUcg0GQmWNwKOgBQ3VzsUEygOhdCEwettinoS2U8juQblRRPbluevXtAW4MR2WmnzkESKSx4HrMy3 TFD78V9DKqT6EJgYy3yxxho+OlUBeNJh1IF1d2IV2qTarakpqusD5h0VN3f0y1NmGWdyUCWF1Muum ByE8qcRxBB24c6HPasXbDvw9nRcbSYax4s2q4Z/BohCiL3VdwEsk4wtVFxObPmdv/1pYdEZqpzQpv UAu3oOIB+8mwRw5BTK8hqoDGQ8rmX4AH9WuqWsWS1jbV3YHcBTFye/mKe5TgcyUREMYNob+KJT3R4 rslcKmOApO8lIb2SiDzw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jBOuw-0003og-LY; Mon, 09 Mar 2020 20:22:26 +0000 Received: from bhuna.collabora.co.uk ([2a00:1098:0:82:1000:25:2eeb:e3e3]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jBOut-0003nY-Kt for linux-arm-kernel@lists.infradead.org; Mon, 09 Mar 2020 20:22:25 +0000 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id EC5F429417A; Mon, 9 Mar 2020 20:22:21 +0000 (GMT) Date: Mon, 9 Mar 2020 21:22:18 +0100 From: Boris Brezillon To: Laurent Pinchart Subject: Re: [PATCH] drm/imx: parallel-display: Adjust bus_flags and bus_format handling Message-ID: <20200309212218.11ac77ae@collabora.com> In-Reply-To: <20200309195926.GC4916@pendragon.ideasonboard.com> References: <20191114131751.26746-1-marex@denx.de> <10f02dbe4e7b0966d279508b636e718e031e2e61.camel@pengutronix.de> <20200309192306.GA20358@pendragon.ideasonboard.com> <20200309205559.3c860aae@collabora.com> <20200309195926.GC4916@pendragon.ideasonboard.com> Organization: Collabora X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200309_132223_815469_DA97ABEF X-CRM114-Status: GOOD ( 28.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marek Vasut , David Airlie , Sascha Hauer , dri-devel@lists.freedesktop.org, NXP Linux Team , Philipp Zabel , Shawn Guo , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 9 Mar 2020 21:59:26 +0200 Laurent Pinchart wrote: > Hi Boris, > > On Mon, Mar 09, 2020 at 08:55:59PM +0100, Boris Brezillon wrote: > > On Mon, 9 Mar 2020 21:23:06 +0200 Laurent Pinchart wrote: > > > On Mon, Mar 09, 2020 at 11:50:59AM +0100, Philipp Zabel wrote: > > > > On Thu, 2019-11-14 at 14:17 +0100, Marek Vasut wrote: > > > > > The bus_flags and bus_format handling logic does not seem to cover > > > > > all potential usecases. Specifically, this seems to fail with an > > > > > "edt,etm0700g0edh6" display attached to an 24bit display interface, > > > > > with interface-pix-fmt = "rgb24" set in DT. > > > > > > > > interface-pix-fmt is a legacy property that was never intended to be > > > > used as an override for the panel bus format. The bus flags were > > > > supposed to be set from the display-timings node, back when there was no > > > > of-graph connected panel at all. > > > > > > > > That being said, there isn't really a proper alternative that allows to > > > > override the bus format requested by the panel driver in the device tree > > > > to account for weird wiring. We could reuse the bus-width endpoint > > > > property documented in [1], but that wouldn't completely specify how the > > > > RGB components are to be mapped onto the parallel bus. > > > > > > > > [1] Documentation/devicetree/bindings/media/video-interfaces.txt > > > > > > Things are funny sometimes, I've run into the exact same problem with a > > > different display controller today. > > > > > > Shouldn't we use the data-shift property from [1] to specify this ? > > > Combined with Boris' bus format negotiation for bridges, I think we > > > would have all the components in place to solve this problem properly. > > > > I wonder if we shouldn't take more complex pin mappings into account > > now and go directly for a data-mapping property describing those > > mappings using a string. This way we'd have a single property that > > would work for both fully parallel buses (DPI/RGB) and serial (or > > partially parallel) ones (LVDS). > > I'm all for standardization, but I'm not sure data-mapping is the right > property, at least with its current definition. It's really meant to > describe how individual bits are mapped to the LVDS time slots. I'm fine > extending it, but we need to define it clearly. How would you envision > it being used in this case ? > Well, clearly the data-width/data-shift approach does not solve all problems: what do you do if the source R pins are connected to the sink B pins? Well, the first answer would probably be 'have a serious discussion with the HW designer responsible for this insanity' :-), but once you've passed this 'WTF' stage, you'll have to find a way to tell the source component it should use RGBxyx while the sink should use BGRxyx (or vice-versa). This is something you can't extract that from those width/shift props though. My suggestion would be to have one string per MEDIA_BUS_FMT definition, so we can force things at the DT level if we really have to. That's basically what the interface-pix-fmt property was doing, except we would standardize the prop and values and probably provide helpers so bridge elements don't have to parse this prop manually. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel