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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=unavailable 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 F1AD3C3F68F for ; Fri, 27 Dec 2019 12:00:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D2774208C4 for ; Fri, 27 Dec 2019 12:00:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726607AbfL0MAL (ORCPT ); Fri, 27 Dec 2019 07:00:11 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:43678 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726354AbfL0MAK (ORCPT ); Fri, 27 Dec 2019 07:00:10 -0500 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 6A14E28A693; Fri, 27 Dec 2019 12:00:07 +0000 (GMT) Date: Fri, 27 Dec 2019 13:00:04 +0100 From: Boris Brezillon To: Marek Szyprowski Cc: dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Inki Dae , Seung-Woo Kim , Andrzej Hajda , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , Laurent Pinchart , Neil Armstrong , Sam Ravnborg , Thierry Reding Subject: Re: [PATCH] drm/bridge: Fix Exynos DSI after making bridge chain a double-linked list Message-ID: <20191227130004.69d7dcad@collabora.com> In-Reply-To: <20191227110135.4961-1-m.szyprowski@samsung.com> References: <20191227110135.4961-1-m.szyprowski@samsung.com> Organization: Collabora X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Dec 2019 12:01:35 +0100 Marek Szyprowski wrote: > Exynos DSI DRM driver uses private calls to out bridge to force certain > order of operations during init/exit sequences. This no longer works after > conversion of bridge chain to a double-linked list. To fix the regression > call bridge related operations manually instead of the generic > drm_bridge_chain_*() operations. I think it'd be worth explaining what the problem is (infinite loop caused by list_for_each_entry() use when the bridge is no longer part of the chain attached to the encoder). > > Signed-off-by: Marek Szyprowski > Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list") We also need to fix that in VC4. > --- > This patch is a result of the following discussion: > https://www.spinics.net/lists/dri-devel/msg239256.html > --- > drivers/gpu/drm/exynos/exynos_drm_dsi.c | 21 ++++++++++++--------- > 1 file changed, 12 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c > index 3955f84dc893..f5905c239a86 100644 > --- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c > +++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c > @@ -255,7 +255,6 @@ struct exynos_dsi { > struct mipi_dsi_host dsi_host; > struct drm_connector connector; > struct drm_panel *panel; > - struct list_head bridge_chain; > struct drm_bridge *out_bridge; > struct device *dev; > > @@ -1391,7 +1390,8 @@ static void exynos_dsi_enable(struct drm_encoder *encoder) > if (ret < 0) > goto err_put_sync; > } else { > - drm_bridge_chain_pre_enable(dsi->out_bridge); > + if (dsi->out_bridge->funcs->pre_enable) > + dsi->out_bridge->funcs->pre_enable(dsi->out_bridge); Okay, so you're calling ->{pre_enable,enable,disable,post_disable}() on the first bridge element which only works if the chain contains one bridge (see below). Maybe you should keep exynos_dsi.bridge_chain and create custom helpers to iterate over chain elements instead of calling those hooks only on out_bridge. > } > > exynos_dsi_set_display_mode(dsi); > @@ -1402,7 +1402,8 @@ static void exynos_dsi_enable(struct drm_encoder *encoder) > if (ret < 0) > goto err_display_disable; > } else { > - drm_bridge_chain_enable(dsi->out_bridge); > + if (dsi->out_bridge->funcs->enable) > + dsi->out_bridge->funcs->enable(dsi->out_bridge); > } > > dsi->state |= DSIM_STATE_VIDOUT_AVAILABLE; > @@ -1427,10 +1428,12 @@ static void exynos_dsi_disable(struct drm_encoder *encoder) > dsi->state &= ~DSIM_STATE_VIDOUT_AVAILABLE; > > drm_panel_disable(dsi->panel); > - drm_bridge_chain_disable(dsi->out_bridge); > + if (dsi->out_bridge->funcs->disable) > + dsi->out_bridge->funcs->disable(dsi->out_bridge); > exynos_dsi_set_display_enable(dsi, false); > drm_panel_unprepare(dsi->panel); > - drm_bridge_chain_post_disable(dsi->out_bridge); > + if (dsi->out_bridge->funcs->post_disable) > + dsi->out_bridge->funcs->post_disable(dsi->out_bridge); > dsi->state &= ~DSIM_STATE_ENABLED; > pm_runtime_put_sync(dsi->dev); > } > @@ -1521,9 +1524,11 @@ static int exynos_dsi_host_attach(struct mipi_dsi_host *host, > > out_bridge = of_drm_find_bridge(device->dev.of_node); > if (out_bridge) { > - drm_bridge_attach(encoder, out_bridge, NULL); > + out_bridge->dev = drm; > + out_bridge->encoder = encoder; > + if (out_bridge->funcs->attach) > + out_bridge->funcs->attach(out_bridge); If you don't want to keep the dsi_exynos.bridge_chain field, you should probably still use drm_bridge_attach() here and manually reset encoder->bridge_chain after checking it only contains a single element. Something like: drm_bridge_attach(encoder, out_bridge, NULL); /* * FIXME: we need to control the enable/disable * sequence to make sure the DSI host controller is * ready to send DSI commands before the * bridge->pre_enable()/panel->prepare() hooks are * called (those hooks are allowed to send DSI * commands). The only way to do that right now is to * reset the bridge chain so that the core thinks it's * empty and turns drm_bridge_chain_xxx() calls into * NOPs. This only works if the chain contains only one * bridge, otherwise we'd be skipping bridge->xxx() * calls on other bridges which is wrong. */ WARN_ON(!list_is_singular(&encoder->bridge_chain)); INIT_LIST_HEAD(&encoder->bridge_chain); Calling ->attach() directly might lead to an invalid pointer dereference if out_bridge tries to attach to another bridge (out_bridge->bridge_node is uninitialized if you don't call drm_bridge_attach()). > dsi->out_bridge = out_bridge; > - list_splice(&encoder->bridge_chain, &dsi->bridge_chain); > } else { > int ret = exynos_dsi_create_connector(encoder); > > @@ -1589,7 +1594,6 @@ static int exynos_dsi_host_detach(struct mipi_dsi_host *host, > if (dsi->out_bridge->funcs->detach) > dsi->out_bridge->funcs->detach(dsi->out_bridge); > dsi->out_bridge = NULL; > - INIT_LIST_HEAD(&dsi->bridge_chain); > } > > if (drm->mode_config.poll_enabled) > @@ -1737,7 +1741,6 @@ static int exynos_dsi_probe(struct platform_device *pdev) > init_completion(&dsi->completed); > spin_lock_init(&dsi->transfer_lock); > INIT_LIST_HEAD(&dsi->transfer_list); > - INIT_LIST_HEAD(&dsi->bridge_chain); > > dsi->dsi_host.ops = &exynos_dsi_ops; > dsi->dsi_host.dev = dev;