From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752482AbdGSD32 (ORCPT ); Tue, 18 Jul 2017 23:29:28 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:39000 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751560AbdGSD31 (ORCPT ); Tue, 18 Jul 2017 23:29:27 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org BE9EC605A8 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> <87mv81bj1r.fsf@eliezer.anholt.net> From: Archit Taneja Message-ID: <69974add-2e5c-0ccf-a0af-7650f19012ef@codeaurora.org> Date: Wed, 19 Jul 2017 08:59:21 +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: <87mv81bj1r.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 07/19/2017 01:43 AM, Eric Anholt wrote: > Archit Taneja writes: > >> 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? > > Yeah. > > >> 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: > > I think instead of extending the struct, we can just walk to the parent > similarly to how of_graph_get_remove_port_parent() does. And fix some > node refcounting at the same time: Yeah, I guess this works. The only thing that's a slight irritant is that we're setting an 'of_node' to a device that doesn't have a DT representation. But I don't have any strong feelings against it. Reviewed-by: Archit Taneja > > diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c > index ed3d505dc203..77d439254da6 100644 > --- a/drivers/gpu/drm/drm_mipi_dsi.c > +++ b/drivers/gpu/drm/drm_mipi_dsi.c > @@ -313,7 +313,12 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host) > * connect our host to it and probe them now. > */ > list_for_each_entry_safe(dsi, temp, &unattached_device_list, list) { > - if (of_get_parent(dsi->dev.of_node) == host->dev->of_node) { > + struct device_node *host_node = of_get_parent(dsi->dev.of_node); > + > + if (!of_node_cmp(host_node->name, "ports")) > + host_node = of_get_next_parent(host_node); > + > + if (host_node == host->dev->of_node) { > dsi->host = host; > dsi->dev.parent = host->dev; > device_initialize(&dsi->dev); > @@ -321,6 +326,8 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host) > mipi_dsi_device_add(dsi); > list_del_init(&dsi->list); > } > + > + of_node_put(host_node); > } > mutex_unlock(&host_lock); > > -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project