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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD856C432BE for ; Fri, 6 Aug 2021 11:01:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EF5E61181 for ; Fri, 6 Aug 2021 11:01:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245273AbhHFLCB convert rfc822-to-8bit (ORCPT ); Fri, 6 Aug 2021 07:02:01 -0400 Received: from aposti.net ([89.234.176.197]:45888 "EHLO aposti.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245261AbhHFLCB (ORCPT ); Fri, 6 Aug 2021 07:02:01 -0400 Date: Fri, 06 Aug 2021 13:01:33 +0200 From: Paul Cercueil Subject: Re: [PATCH 2/2] gpu/drm: ingenic: Add workaround for disabled drivers To: Greg Kroah-Hartman Cc: Rob Herring , "Rafael J . Wysocki" , David Airlie , Daniel Vetter , Sam Ravnborg , list@opendingux.net, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, dri-devel@lists.freedesktop.org Message-Id: In-Reply-To: References: <20210805192110.90302-1-paul@crapouillou.net> <20210805192110.90302-3-paul@crapouillou.net> <3HUDXQ.7RBGD4FUHR2F@crapouillou.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Hi Greg, Le ven., août 6 2021 at 12:17:55 +0200, Greg Kroah-Hartman a écrit : > On Thu, Aug 05, 2021 at 10:05:27PM +0200, Paul Cercueil wrote: >> Hi Greg, >> >> Le jeu., août 5 2021 at 21:35:34 +0200, Greg Kroah-Hartman >> a écrit : >> > On Thu, Aug 05, 2021 at 09:21:09PM +0200, Paul Cercueil wrote: >> > > When the drivers of remote devices (e.g. HDMI chip) are >> disabled in >> > > the >> > > config, we want the ingenic-drm driver to be able to probe >> > > nonetheless >> > > with the other devices (e.g. internal LCD panel) that are >> enabled. >> > > >> > > Signed-off-by: Paul Cercueil >> > > --- >> > > drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 12 ++++++++++++ >> > > 1 file changed, 12 insertions(+) >> > > >> > > diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> > > b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> > > index d261f7a03b18..5e1fdbb0ba6b 100644 >> > > --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> > > +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c >> > > @@ -1058,6 +1058,18 @@ static int ingenic_drm_bind(struct >> device >> > > *dev, bool has_components) >> > > for (i = 0; ; i++) { >> > > ret = drm_of_find_panel_or_bridge(dev->of_node, 0, i, >> &panel, >> > > &bridge); >> > > if (ret) { >> > > + /* >> > > + * Workaround for the case where the drivers for the >> > > + * remote devices are not enabled. When that happens, >> > > + * drm_of_find_panel_or_bridge() returns -EPROBE_DEFER >> > > + * endlessly, which prevents the ingenic-drm driver from >> > > + * working at all. >> > > + */ >> > > + if (ret == -EPROBE_DEFER) { >> > > + ret = driver_deferred_probe_check_state(dev); >> > > + if (ret == -ENODEV || ret == -ETIMEDOUT) >> > > + continue; >> > > + } >> > >> > So you are mucking around with devices on other busses within this >> > driver? What could go wrong? :( >> >> I'm doing the same thing as everybody else. This is the DRM driver, >> and >> there is a driver for the external HDMI chip which gives us a DRM >> bridge >> that we can obtain from the device tree. > > But then why do you need to call this function that is there for a > bus, > not for a driver. The documentation disagrees with you :) And, if that has any weight, this solution was proposed by Rob. >> > Please use the existing driver core functionality for this type of >> > thing, it is not unique, no need for this function to be called. >> >> I'm not sure you understand what I'm doing here. This driver calls >> drm_of_find_panel_or_bridge(), without guarantee that the driver >> for the >> remote device (connected via DT graph) has been enabled in the >> kernel >> config. In that case it will always return -EPROBE_DEFER and the >> ingenic-drm >> driver will never probe. >> >> This patch makes sure that the driver can probe if the HDMI driver >> has been >> disabled in the kernel config, nothing more. > > That should not be an issue as you do not care if the config is > enabled, > you just want to do something in the future if the driver shows up, > right? Well, the DRM subsystem doesn't really seem to handle hotplug of hardware. Right now all the drivers for the connected hardware need to probe before the main DRM driver. So I need to know that a remote device (connected via DT graph) will never probe. Give me a of_graph_remote_device_driver_will_never_probe() and I'll use that. > Much like the device link code, have you looked at that? I don't see how that would help in any way. The device link code would allow me to set a dependency between the remote hardware (HDMI chip, provider) and the LCD controller (consumer), but I already have that dependency though the DT graph. What I need is a way for the consumer to continue probing if the provider is not going to probe. Cheers, -Paul