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 00057C6FD1D for ; Mon, 20 Mar 2023 14:00:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231561AbjCTOAg (ORCPT ); Mon, 20 Mar 2023 10:00:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51822 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231544AbjCTOAP (ORCPT ); Mon, 20 Mar 2023 10:00:15 -0400 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 EC9C21206C; Mon, 20 Mar 2023 07:00:09 -0700 (PDT) Received: from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi [213.243.189.158]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 6EAF4A25; Mon, 20 Mar 2023 15:00:06 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1679320806; bh=IG/Ir90hcp4I1UHRmwtxnVj3+qNUDUJWDkrsBZJN4gg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qyAMbXQ/f0E1sZvnkwuRRhBTGA8pBu+c4i7tF2uQErqLbeASllho8Km8tZG4TfrG9 7hp9ySO1weLJIsJR6WbkP3GXqCP4ZIqlLZclmQxMt1T9Jjpkr8wkVSLT9OnYmsF19f rYjaOJ8Bi4dbaoWwI1pwRBcigUAMBY7b5ITHonOk= Date: Mon, 20 Mar 2023 16:00:12 +0200 From: Laurent Pinchart To: Philipp Zabel Cc: Sakari Ailus , Jacopo Mondi , Francesco Dolcini , Sakari Ailus , Marcel Ziswiler , linux-media@vger.kernel.org, kernel@pengutronix.de, Francesco Dolcini , Aishwarya Kothari , Marcel Ziswiler , Mauro Carvalho Chehab , Steve Longerbeam , linux-kernel@vger.kernel.org, Marco Felsch Subject: Re: [PATCH v2] media: i2c: ov5640: Implement get_mbus_config Message-ID: <20230320140012.GB9535@pendragon.ideasonboard.com> References: <20230320084844.tdjiv6kaxcosiwm2@uno.localdomain> <20230320092602.GE20234@pendragon.ideasonboard.com> <20230320095514.GF20234@pendragon.ideasonboard.com> <727949a9c3d9e639b046bcd86635796452b10300.camel@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <727949a9c3d9e639b046bcd86635796452b10300.camel@pengutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 20, 2023 at 02:32:25PM +0100, Philipp Zabel wrote: > On Mo, 2023-03-20 at 12:15 +0200, Sakari Ailus wrote: > > On Mon, Mar 20, 2023 at 11:55:14AM +0200, Laurent Pinchart wrote: > > > On Mon, Mar 20, 2023 at 11:37:33AM +0200, Sakari Ailus wrote: > > > > On Mon, Mar 20, 2023 at 11:26:02AM +0200, Laurent Pinchart wrote: > > > > > In a (simplified) nutshell, > > > > > > > > > > ---------+ +----------+ +---------+ +-----+ +-----+ > > > > > > Camera | --> | CSI-2 RX | --> | CSI2IPU | --> | Mux | --> | IPU | > > > > > > Sensor | | | | Gasket | | | | | > > > > > ---------+ +----------+ +---------+ +-----+ +-----+ > > > > > > > > Thank you, this is helpful. > > > > > > > > I suppose the mux here at least won't actively do anything to the data. So > > > > presumably its endpoint won't contain the active configuration, but its > > > > superset. > > > > > > > > > > > > > > All those blocks, except for the gasket, have a node in DT. > > > > > > > > > > The IPU driver needs to know the number of CSI-2 data lanes, which is > > > > > encoded in the data-lanes DT property present in both the sensor output > > > > > endpoint and the CSI-2 RX input endpoint, but not the other endpoints in > > > > > the pipeline. > > > > > > > > This doesn't yet explain why the sensor would need to implement > > > > get_mbus_config if its bus configuration remains constant. > > > > > > If I recall correctly, the IPU driver calls .g_mbus_config() on the > > > camera sensor to get the number of lanes, as it can't get it from its > > > own endpoint. That's a hack, and as Jacopo proposed, calling > > > .g_mbus_config() on the CSI-2 RX would be better, as the CSI-2 RX driver > > > can then get the value from its own endpoint, without requiring all > > > sensor drivers to implement .g_mbus_config(). > > > > The g_mbus_config op could be implemented by the CSI2IPU and mux, by simply > > requesting the information from the upstream sub-device. No hacks would be > > needed. > > I think implementing get_mbus_config on the mux might be enough. The > IPU driver already recognizes the CSI-2 RX by its grp_id and could > infer that it has to use MIPI CSI-2 mode from that. > > The video-mux would have to forward get_mbus_config to its active > upstream port and if the upstream sensor does not implement it read bus > width from the active upstream endpoint. I'm fine with implementing it in the mux as well, but I think we can take a shortcut here and call it on the CSI-2 RX from the IPU driver, as the IPU driver knows about the architecture of the whole pipeline. -- Regards, Laurent Pinchart