From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751280AbdGQE06 (ORCPT ); Mon, 17 Jul 2017 00:26:58 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:46500 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751093AbdGQE05 (ORCPT ); Mon, 17 Jul 2017 00:26:57 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 9679D6121C Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=architt@codeaurora.org Subject: Re: [PATCH 6/8] drm: Allow DSI devices to be registered before the host registers. To: Eric Anholt , dri-devel@lists.freedesktop.org, Andrzej Hajda , Laurent Pinchart , Thierry Reding Cc: linux-kernel@vger.kernel.org, Boris Brezillon References: <20170627195839.3338-1-eric@anholt.net> <20170627195839.3338-7-eric@anholt.net> <6fbaa797-1040-48e8-c361-dad4363cd30d@codeaurora.org> <87vamu7hi4.fsf@eliezer.anholt.net> From: Archit Taneja Message-ID: Date: Mon, 17 Jul 2017 09:56:49 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <87vamu7hi4.fsf@eliezer.anholt.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/15/2017 04:28 AM, Eric Anholt wrote: > Archit Taneja writes: > >> On 06/28/2017 01:28 AM, Eric Anholt wrote: >>> When a mipi_dsi_host is registered, the DT is walked to find any child >>> nodes with compatible strings. Those get registered as DSI devices, >>> and most DSI panel drivers are mipi_dsi_drivers that attach to those nodes. >>> >>> There is one special case currently, the adv7533 bridge, where the >>> bridge probes on I2C, and during the bridge attach step it looks up >>> the mipi_dsi_host and registers the mipi_dsi_device (for its own stub >>> mipi_dsi_driver). >>> >>> For the Raspberry Pi panel, though, we also need to attach on I2C (our >>> control bus), but don't have a bridge driver. The lack of a bridge's >>> attach() step like adv7533 uses means that we aren't able to delay the >>> mipi_dsi_device creation until the mipi_dsi_host is present. >>> >>> To fix this, we extend mipi_dsi_device_register_full() to allow being >>> called with a NULL host, which puts the device on a queue waiting for >>> a host to appear. When a new host is registered, we fill in the host >>> value and finish the device creation process. >> >> This is quite a nice idea. The only bothering thing is the info.of_node usage >> varies between child nodes (mipi_dsi_devs) and non-child nodes (i2c control >> bus). >> >> For DSI children expressed in DT, the of_node in info holds the DT node >> corresponding to the DSI child itself. For non-DT ones, this patch assumes >> that info.of_node stores the DSI host DT node. I think it should be okay as >> long as we mention the usage in a comment somewhere. The other option is to >> have a new info.host_node field to keep a track of the host DT node. > > I think maybe you misread the patch? We're using > of_get_parent(dsi->dev.node), which came from info->node, to compare to > host->dev->of_node(). I think I did misread it. Although, I'm not entirely clear what we should be setting info.node to. In patch #8, info.node is set by: endpoint = of_graph_get_next_endpoint(dev->of_node, NULL); info.node = of_graph_get_remote_port(endpoint); Looking at the dt bindings in patch #7, it looks like info.node is set to the 'port' device node in dsi@7e700000, is that right? I suppose 'port' here seems like a reasonable representation of dsi->dev.node, I wonder how it would work if the dsi host had multiple ports underneath it. I.e: dsi@7e700000 { ... ... ports { port@0 { ... dsi_out_port: endpoint { remote-endpoint = <&panel_dsi_port>; }; }; port@1 { ... ... }; }; }; Here, we would need to set info.node to the 'ports' node, so that of_get_parent(dsi->dev.of_node) equals host->dev->of_node. That doesn't seem correct. Ideally, a dev's 'of_node' should be left to NULL if we don't have a corresponding OF node. We're sort of overriding it here since we don't have any other place to store this information in the mipi_dsi_device struct. Maybe we could add a 'host_node' entry in mipi_dsi_device itself, which is exclusively used cases where the DSI device doesn't have a DT node. Our check in mipi_dsi_host_register() could then be something like: if (dsi->host_node) == host->dev->of_node) { ... ... } Since Thierry also reviews drm_mipi_dsi.c changes, it would nice to get some comments from him too. Thanks, Archit -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project