From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759015AbcIWNN1 (ORCPT ); Fri, 23 Sep 2016 09:13:27 -0400 Received: from mail-lf0-f68.google.com ([209.85.215.68]:36812 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757419AbcIWNNZ (ORCPT ); Fri, 23 Sep 2016 09:13:25 -0400 Date: Fri, 23 Sep 2016 15:13:15 +0200 From: Daniel Vetter To: Brian Starkey Cc: Daniel Vetter , Liviu Dudau , Sean Paul , Russell King - ARM Linux , Linux Kernel Mailing List , dri-devel Subject: Re: [PATCH] drm/i2c: tda998x: don't register the connector Message-ID: <20160923131315.GI3988@dvetter-linux.ger.corp.intel.com> Mail-Followup-To: Brian Starkey , Liviu Dudau , Sean Paul , Russell King - ARM Linux , Linux Kernel Mailing List , dri-devel References: <20160921085738.GA27277@e106950-lin.cambridge.arm.com> <20160921162803.GS1041@n2100.armlinux.org.uk> <20160922103917.GA5632@e106950-lin.cambridge.arm.com> <20160922105155.GT1041@n2100.armlinux.org.uk> <20160922141404.GA5222@e106950-lin.cambridge.arm.com> <20160923093416.GU8917@e106497-lin.cambridge.arm.com> <20160923125248.GA23321@e106950-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160923125248.GA23321@e106950-lin.cambridge.arm.com> X-Operating-System: Linux dvetter-linux.ger.corp.intel.com 4.6.7-300.fc24.x86_64 User-Agent: Mutt/1.7.0 (2016-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 23, 2016 at 01:52:49PM +0100, Brian Starkey wrote: > On Fri, Sep 23, 2016 at 12:58:46PM +0200, Daniel Vetter wrote: > > On Fri, Sep 23, 2016 at 11:34 AM, Liviu Dudau wrote: > > > rmmod-ing the hdlcd module generates a WARN() splat as the vsync is still > > > enabled, but we never got the call to turn off the CRTC. Brian is still > > > tracking through the fbdev emulation to figure out the cause for that. > > > > fbdev emulation doesn't do that for you. If you need/want to shut down > > all the crtcs on driver unload, you need to do that yourself. There's > > atomic helpers to do that for you that for you. > > The problem is a sort-of circular dependency between ->lastclose (at > least the common implementation of it), unregister and disabling > fbdev. > > I want to move drm_dev_unregister() to be the first thing we do at > rmmod-time. However we need to disable fbdev first, otherwise > ->lastclose restores the fbdev mode, guaranteeing that vsync is turned > on for drm_vsync_cleanup() to then WARN on. > > There's a slightly different (perceived) problem - the one that Liviu > mentions - that drm_fbdev_cma_fini() doesn't disable the CRTC anyway. > You say it's not the fbdev helpers' responsibility to teardown their > modeset, but regardless I have nowhere to disable the CRTC if I want > to do drm_dev_unregister() first; and if the CRTC isn't disabled > there's always a chance of hitting the same vsync WARN even without > fbdev. Just disable all crtc in a suitable place (after drm_dev_unregister, before you tear down fbdev). > > We *could* add an ->unload and disable everything there, but as that's > deprecated I'm guessing there should be another way. > Perhaps we should track ->firstopen/->lastclose pairs so we can detect > that ->lastclose is being called from unregister and use it to > disable everything in that case. Hm, maybe we should simply not call ->lastclose for kms drivers. That is kinda only a hack for ums/dri1 drivers. But even with that gone you might still unload while fbdev is enabled, so this won't fix it all. > drm_vblank_cleanup() seems to have been carried over to unregister > from drm_put_dev(), but drm_dev_register() doesn't call > drm_vblank_init() so it seems a little strange to have it there. > I can see other drivers I'd expect to hit the same WARN but I don't > have HW to test it on. Oops. That call to drm_vblank_cleanup() really shouldn't be in there. We should push it into all callers instead I think. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch