From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0542D49620; Fri, 1 Nov 2024 14:43:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730472207; cv=none; b=T5m3vmvWPqFytHLQxopfTCsN1mKNyhyS+K79sLGbf1crmEfqlciieTMAgvDW6M7kAFZKoZGgRwYXiRYa5dkr1mCUHH30CIl/+Xjol4+iHG65vo3LZI+TxUW+TPdExPkEXoRlikqgO24BR2grfKgvgtfdBICfmNL/8kIeIVYWC4k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730472207; c=relaxed/simple; bh=DZWLfHW2eJhePPE3Q0nswhlD0ECMPDjCzq0Ko2Z40oY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ijy2d5q+FWkA7CBzXk8k8P6Q0SDBIx1F+7XbKOJZ9aQXS6DeocDqGN6Y4sKW1m/UDZnHteJm3yjVdR02YsPpyKE/6W6W+6YKsMWNLLMRUxJvKcwW/fkGcILtEfBs04/BCK7O1RTJB9DRPj7MCKL8J/nRXLgH5HGu59QsUJq6mo8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=MWSY2wEu; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="MWSY2wEu" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id C7B5A3A2; Fri, 1 Nov 2024 15:43:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1730472198; bh=DZWLfHW2eJhePPE3Q0nswhlD0ECMPDjCzq0Ko2Z40oY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MWSY2wEuc6Qj4FjBO1cBCoPs8MjJsah9QmCwk1mYCY9KoN9I2sQ1ACQPh9nnYAIF4 XZI7POtpBEFYQMIMKaRhw6/NII7D3A0NpY0kmHqscG5E/j11ZbdJhvWZsMTs0qX+Jg U0kWOWPi7wXFI6a3uSYYB8XQ01MXInSjzYigHdP0= Date: Fri, 1 Nov 2024 16:43:15 +0200 From: Laurent Pinchart To: Dmitry Baryshkov Cc: Sui Jingfeng , Johan Hovold , neil.armstrong@linaro.org, Andrzej Hajda , Robert Foss , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Abel Vesa , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] drm/bridge: Fix assignment of the of_node of the parent to aux bridge Message-ID: <20241101144315.GK2473@pendragon.ideasonboard.com> References: <20241018-drm-aux-bridge-mark-of-node-reused-v2-1-aeed1b445c7d@linaro.org> <172951608323.1285208.3162107667310691864.b4-ty@linaro.org> <230b5910-6790-44cb-90ed-222bee89054d@linux.dev> <751a4ab5-acbf-4e57-8cf4-51ab10206cc9@linux.dev> <30fefafc-d19a-40cb-bcb1-3c586ba8e67e@linux.dev> <20241101092049.GJ2473@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Fri, Nov 01, 2024 at 12:27:15PM +0200, Dmitry Baryshkov wrote: > On Fri, 1 Nov 2024 at 11:20, Laurent Pinchart wrote: > > On Fri, Nov 01, 2024 at 11:49:07AM +0800, Sui Jingfeng wrote: > > > On 2024/11/1 00:23, Johan Hovold wrote: > > > > On Thu, Oct 31, 2024 at 11:06:38PM +0800, Sui Jingfeng wrote: > > > > > > > >> But I think Johan do need more times to understand what exactly > > > >> the real problem is. We do need times to investigate new method. > > > > No, I know perfectly well what the (immediate) problem is here (I was > > > > the one adding support for the of_node_reused flag some years back). > > > > > > > > I just wanted to make sure that the commit message was correct and > > > > complete before merging (and also to figure out whether this particular > > > > patch needed to be backported). > > > > > > Well under such a design, having the child device sharing the 'OF' device > > > node with it parent device means that one parent device can *only* > > > create one AUX bridge child device. > > > > > > Since If you create two or more child AUX bridge, *all* of them will > > > call devm_drm_of_get_bridge(&auxdev->dev, auxdev->dev.of_node, 0, 0), > > > then we will *contend* the same next bridge resource. > > > > > > Because of the 'auxdev->dev.of_node' is same for all its instance. > > > While other display bridges seems don't has such limitations. > > > > Brainstorming a bit, I wonder if we could create a swnode for the > > auxiliary device, instead of reusing the parent's OF node. > > This will break bridge lookup which is performed by following the OF > graph links. So the aux bridges should use corresponding of_node or > fwnode. We can also expand the lookup infrastructure and handle more platform integration and driver architecture options. I'm not sure how it would look like, but all these are in-kernel APIs, so they can be extended and modified if needed. > > This would > > require switching the DRM OF-based APIs to fwnode, but that's easy and > > mostly a mechanical change. -- Regards, Laurent Pinchart