From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752375AbeEGNxu (ORCPT ); Mon, 7 May 2018 09:53:50 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:36044 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752098AbeEGNxp (ORCPT ); Mon, 7 May 2018 09:53:45 -0400 X-Google-Smtp-Source: AB8JxZqkMBJpMbFwiuy6zDzUUVFGpLp9UM4HiAE+aCjImauixGlhafxW9JKfatcV6UF2WexrCxc4Ow== Date: Mon, 7 May 2018 15:53:41 +0200 From: Daniel Vetter To: Andrzej Hajda Cc: Peter Rosin , linux-kernel@vger.kernel.org, Archit Taneja , Laurent Pinchart , David Airlie , Peter Senna Tschudin , Martin Donnelly , Martyn Welch , Gustavo Padovan , Maarten Lankhorst , Sean Paul , Inki Dae , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Kukjin Kim , Krzysztof Kozlowski , CK Hu , Philipp Zabel , Matthias Brugger , Rob Clark , Sandy Huang , Heiko =?iso-8859-1?Q?St=FCbner?= , Benjamin Gaignard , Vincent Abriou , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org, linux-rockchip@lists.infradead.org, Jyri Sarha , Daniel Vetter Subject: Re: [PATCH v2 26/26] drm/bridge: establish a link between the bridge supplier and consumer Message-ID: <20180507135341.GI12521@phenom.ffwll.local> Mail-Followup-To: Andrzej Hajda , Peter Rosin , linux-kernel@vger.kernel.org, Archit Taneja , Laurent Pinchart , David Airlie , Peter Senna Tschudin , Martin Donnelly , Martyn Welch , Gustavo Padovan , Maarten Lankhorst , Sean Paul , Inki Dae , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Kukjin Kim , Krzysztof Kozlowski , CK Hu , Philipp Zabel , Matthias Brugger , Rob Clark , Sandy Huang , Heiko =?iso-8859-1?Q?St=FCbner?= , Benjamin Gaignard , Vincent Abriou , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org, linux-rockchip@lists.infradead.org, Jyri Sarha References: <20180504135212.26977-1-peda@axentia.se> <20180504135212.26977-27-peda@axentia.se> <4cdcd215-8caf-e045-a478-f438f128c9f2@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4cdcd215-8caf-e045-a478-f438f128c9f2@samsung.com> X-Operating-System: Linux phenom 4.15.0-3-amd64 User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 07, 2018 at 02:59:45PM +0200, Andrzej Hajda wrote: > On 04.05.2018 15:52, Peter Rosin wrote: > > If the bridge supplier is unbound, this will bring the bridge consumer > > down along with the bridge. Thus, there will no longer linger any > > dangling pointers from the bridge consumer (the drm_device) to some > > non-existent bridge supplier. > > I understand rationales behind this patch, but it is another step into > making drm_dev one big driver with subcomponents, where drm will work > only if every subcomponent is working/loaded. Do we need to go this way? > In case of many platforms such approach results in display turned on > very late on boot for example due to late initialization of some > regulator exposed by some i2c device, which is used by hdmi bridge. And > this hdmi bridge is just to provide alternative(rarely used) display > path, the main display path would work anyway. > > So the main question to drm maintainers is about evolution of bridges, > if drm_bridges should become mandatory components of drm device or they > could be added/removed dynamically? This is already the case. You currently cannot hotplug a drm_bridge, everything must be present. I don't think it makes sense to change that until we have physically hotpluggable drm_bridges in real hardware. I definitely don't want to refcount stuff to work around driver load bonghits on DT platforms, because refcounting is way too hard to get right :-) Afaik there's out-of-tree patches to solve 99% of the driver load fun on DT platforms, but because it's not a 100% solution it's blocked since forever. -Daniel > > Regards > Andrzej > > > > > > Signed-off-by: Peter Rosin > > --- > > drivers/gpu/drm/drm_bridge.c | 18 ++++++++++++++++++ > > include/drm/drm_bridge.h | 2 ++ > > 2 files changed, 20 insertions(+) > > > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c > > index 78d186b6831b..0259f0a3ff27 100644 > > --- a/drivers/gpu/drm/drm_bridge.c > > +++ b/drivers/gpu/drm/drm_bridge.c > > @@ -26,6 +26,7 @@ > > #include > > > > #include > > +#include > > #include > > > > #include "drm_crtc_internal.h" > > @@ -127,12 +128,25 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge, > > if (bridge->dev) > > return -EBUSY; > > > > + if (encoder->dev->dev != bridge->odev) { > > + bridge->link = device_link_add(encoder->dev->dev, > > + bridge->odev, 0); > > + if (!bridge->link) { > > + dev_err(bridge->odev, "failed to link bridge to %s\n", > > + dev_name(encoder->dev->dev)); > > + return -EINVAL; > > + } > > + } > > + > > bridge->dev = encoder->dev; > > bridge->encoder = encoder; > > > > if (bridge->funcs->attach) { > > ret = bridge->funcs->attach(bridge); > > if (ret < 0) { > > + if (bridge->link) > > + device_link_del(bridge->link); > > + bridge->link = NULL; > > bridge->dev = NULL; > > bridge->encoder = NULL; > > return ret; > > @@ -159,6 +173,10 @@ void drm_bridge_detach(struct drm_bridge *bridge) > > if (bridge->funcs->detach) > > bridge->funcs->detach(bridge); > > > > + if (bridge->link) > > + device_link_del(bridge->link); > > + bridge->link = NULL; > > + > > bridge->dev = NULL; > > } > > > > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h > > index b656e505d11e..804189c63a4c 100644 > > --- a/include/drm/drm_bridge.h > > +++ b/include/drm/drm_bridge.h > > @@ -261,6 +261,7 @@ struct drm_bridge_timings { > > * @list: to keep track of all added bridges > > * @timings: the timing specification for the bridge, if any (may > > * be NULL) > > + * @link: drm consumer <-> bridge supplier > > * @funcs: control functions > > * @driver_private: pointer to the bridge driver's internal context > > */ > > @@ -271,6 +272,7 @@ struct drm_bridge { > > struct drm_bridge *next; > > struct list_head list; > > const struct drm_bridge_timings *timings; > > + struct device_link *link; > > > > const struct drm_bridge_funcs *funcs; > > void *driver_private; > > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch