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 00397C4338F for ; Fri, 6 Aug 2021 11:01:45 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B86CE61181 for ; Fri, 6 Aug 2021 11:01:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B86CE61181 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=crapouillou.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E82496E8BD; Fri, 6 Aug 2021 11:01:44 +0000 (UTC) Received: from aposti.net (aposti.net [89.234.176.197]) by gabe.freedesktop.org (Postfix) with ESMTPS id 89EA36E8BD for ; Fri, 6 Aug 2021 11:01:43 +0000 (UTC) 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: quoted-printable X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Greg, Le ven., ao=FBt 6 2021 at 12:17:55 +0200, Greg Kroah-Hartman=20 a =E9crit : > On Thu, Aug 05, 2021 at 10:05:27PM +0200, Paul Cercueil wrote: >> Hi Greg, >>=20 >> Le jeu., ao=FBt 5 2021 at 21:35:34 +0200, Greg Kroah-Hartman >> a =E9crit : >> > On Thu, Aug 05, 2021 at 09:21:09PM +0200, Paul Cercueil wrote: >> > > When the drivers of remote devices (e.g. HDMI chip) are=20 >> 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=20 >> 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=20 >> device >> > > *dev, bool has_components) >> > > for (i =3D 0; ; i++) { >> > > ret =3D drm_of_find_panel_or_bridge(dev->of_node, 0, i,=20 >> &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 =3D=3D -EPROBE_DEFER) { >> > > + ret =3D driver_deferred_probe_check_state(dev); >> > > + if (ret =3D=3D -ENODEV || ret =3D=3D -ETIMEDOUT) >> > > + continue; >> > > + } >> > >> > So you are mucking around with devices on other busses within this >> > driver? What could go wrong? :( >>=20 >> I'm doing the same thing as everybody else. This is the DRM driver,=20 >> and >> there is a driver for the external HDMI chip which gives us a DRM=20 >> bridge >> that we can obtain from the device tree. >=20 > But then why do you need to call this function that is there for a=20 > 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. >>=20 >> 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=20 >> for the >> remote device (connected via DT graph) has been enabled in the=20 >> kernel >> config. In that case it will always return -EPROBE_DEFER and the=20 >> ingenic-drm >> driver will never probe. >>=20 >> This patch makes sure that the driver can probe if the HDMI driver=20 >> has been >> disabled in the kernel config, nothing more. >=20 > That should not be an issue as you do not care if the config is=20 > 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=20 hardware. Right now all the drivers for the connected hardware need to=20 probe before the main DRM driver. So I need to know that a remote=20 device (connected via DT graph) will never probe. Give me a of_graph_remote_device_driver_will_never_probe() and I'll use=20 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=20 allow me to set a dependency between the remote hardware (HDMI chip,=20 provider) and the LCD controller (consumer), but I already have that=20 dependency though the DT graph. What I need is a way for the consumer=20 to continue probing if the provider is not going to probe. Cheers, -Paul