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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 33337EB8FD5 for ; Wed, 6 Sep 2023 13:38:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241173AbjIFNiW (ORCPT ); Wed, 6 Sep 2023 09:38:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38118 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240979AbjIFNiV (ORCPT ); Wed, 6 Sep 2023 09:38:21 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B2DD10C7; Wed, 6 Sep 2023 06:38:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1694007497; x=1725543497; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=l0yqPyXeMtkEe7eJDRu4uOHmMf5EFulFbVZ32U4Q2G4=; b=C8+FUnuonfrByuLMbAMzOarWDy4/ITFz4K27RaBZUTS56tg/EOxF95Pr O1SoGfJ/8kEjn5PhZ2mRf1i9Zf9CpX86IKBzGLC9mYPCpwGJdHE7xxBAb PUeYYCJ1KNY0n5QEgFL6rKlpit/ZT76+xr1q9csaGLEPlFtWUCvgK4yDf sxD0wy7DHitXV9H/ABJL5db1ATKdwBVJuBGwt8V4CompFkTnSfRiPIJ8+ Dbsh28mMHvODj5yZXSh9qNiU4cQBHxh82U4OoaWm3Ef+gcvO1YFWhkk3D kPZN5OD79sq515kdOzWB9udwj8AptR/uWK7uygDqk/YYSL/ZLY3nqf5dZ g==; X-IronPort-AV: E=McAfee;i="6600,9927,10825"; a="362097849" X-IronPort-AV: E=Sophos;i="6.02,232,1688454000"; d="scan'208";a="362097849" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Sep 2023 06:38:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10825"; a="735049955" X-IronPort-AV: E=Sophos;i="6.02,232,1688454000"; d="scan'208";a="735049955" Received: from kuha.fi.intel.com ([10.237.72.185]) by orsmga007.jf.intel.com with SMTP; 06 Sep 2023 06:38:08 -0700 Received: by kuha.fi.intel.com (sSMTP sendmail emulation); Wed, 06 Sep 2023 16:38:08 +0300 Date: Wed, 6 Sep 2023 16:38:08 +0300 From: Heikki Krogerus To: Dmitry Baryshkov Cc: David Airlie , Daniel Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Bryan O'Donoghue , Guenter Roeck , Janne Grunau , Simon Ser , Andy Gross , Bjorn Andersson , Konrad Dybcio , Greg Kroah-Hartman , dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, freedreno@lists.freedesktop.org, Won Chung Subject: Re: [RFC PATCH v1 01/12] Revert "drm/sysfs: Link DRM connectors to corresponding Type-C connectors" Message-ID: References: <20230903214150.2877023-1-dmitry.baryshkov@linaro.org> <20230903214150.2877023-2-dmitry.baryshkov@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, Sep 06, 2023 at 03:48:35PM +0300, Dmitry Baryshkov wrote: > On Wed, 6 Sept 2023 at 15:44, Heikki Krogerus > wrote: > > > > On Tue, Sep 05, 2023 at 01:56:59PM +0300, Dmitry Baryshkov wrote: > > > Hi Heikki, > > > > > > On Tue, 5 Sept 2023 at 11:50, Heikki Krogerus > > > wrote: > > > > > > > > Hi Dmitry, > > > > > > > > On Mon, Sep 04, 2023 at 12:41:39AM +0300, Dmitry Baryshkov wrote: > > > > > The kdev->fwnode pointer is never set in drm_sysfs_connector_add(), so > > > > > dev_fwnode() checks never succeed, making the respective commit NOP. > > > > > > > > That's not true. The dev->fwnode is assigned when the device is > > > > created on ACPI platforms automatically. If the drm_connector fwnode > > > > member is assigned before the device is registered, then that fwnode > > > > is assigned also to the device - see drm_connector_acpi_find_companion(). > > > > > > > > But please note that even if drm_connector does not have anything in > > > > its fwnode member, the device may still be assigned fwnode, just based > > > > on some other logic (maybe in drivers/acpi/acpi_video.c?). > > > > > > > > > And if drm_sysfs_connector_add() is modified to set kdev->fwnode, it > > > > > breaks drivers already using components (as it was pointed at [1]), > > > > > resulting in a deadlock. Lockdep trace is provided below. > > > > > > > > > > Granted these two issues, it seems impractical to fix this commit in any > > > > > sane way. Revert it instead. > > > > > > > > I think there is already user space stuff that relies on these links, > > > > so I'm not sure you can just remove them like that. If the component > > > > framework is not the correct tool here, then I think you need to > > > > suggest some other way of creating them. > > > > > > The issue (that was pointed out during review) is that having a > > > component code in the framework code can lead to lockups. With the > > > patch #2 in place (which is the only logical way to set kdev->fwnode > > > for non-ACPI systems) probing of drivers which use components and set > > > drm_connector::fwnode breaks immediately. > > > > > > Can we move the component part to the respective drivers? With the > > > patch 2 in place, connector->fwnode will be copied to the created > > > kdev's fwnode pointer. > > > > > > Another option might be to make this drm_sysfs component registration optional. > > > > You don't need to use the component framework at all if there is > > a better way of determining the connection between the DP and its > > Type-C connector (I'm assuming that that's what this series is about). > > You just need the symlinks, not the component. > > The problem is that right now this component registration has become > mandatory. And if I set the kdev->fwnode manually (like in the patch > 2), the kernel hangs inside the component code. > That's why I proposed to move the components to the place where they > are really necessary, e.g. i915 and amd drivers. So why can't we replace the component with the method you are proposing in this series of finding out the Type-C port also with i915, AMD, or whatever driver and platform (that's the only thing that component is used for)? Determining the connection between a DP and its Type-C connector is starting to get really important, so ideally we have a common solution for that. thanks, -- heikki