From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20EBA606A33D for ; Thu, 22 Oct 2026 13:42:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=fot5chN1 Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 83B751125DC; Thu, 22 Oct 2026 13:42:00 +0000 (UTC) Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id E70331125DC for ; Thu, 22 Oct 2026 13:41:53 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 9C3EA416EE; Thu, 22 Oct 2026 13:41:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2E34E1F000C1; Thu, 22 Oct 2026 13:41:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792676513; bh=rhL1r81qt/J+n11F3Lr+ZU1b0+/pO8cTtjyKspANkt0=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=fot5chN1OHuyeOb8+EAbp2FFPFK77tyv6CPzPAMFGzk9xfYAEP6M5I1+N8EdW0iUq uoH/uGAGJbCqycLhHNxDI0/Ee4Ssw/zyznwRBDaZyb4kzDf0KgHQ0s7IbSUaVHxJvx Io2xwABjdA2tC7w3WfKR3MykKeMZJRYWV4ZofsI7IVmJVGzku9JBRzw9o6SJEs1UvY bO+v0xR7TRyCm20Syy2dNxRTAkHK9eomu0HxqFHfq9lToswEdHDfb/NZ1f7CVSAvNo uHvejaimOj9G1tUfFy4a8dbLUIBSToM6YUF0+rY33m6QonuanFLgtd3CQd7nZ1HdTT 8Z5i0eYNLB3/A== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v4 5/7] drm/tegra: rgb: Parameterize configuration based on bus flags To: "Svyatoslav Ryhel" Cc: dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, robh@kernel.org, conor+dt@kernel.org In-Reply-To: <20261022132259.240717-6-clamor95@gmail.com> References: <20261022132259.240717-1-clamor95@gmail.com> <20261022132259.240717-6-clamor95@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 22 Oct 2026 13:41:52 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "dri-devel" X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] drm/tegra: unlocked bridge state access in tegra_rgb_encoder_enabl= e() -- commit 743a0ce150c28976e990ee80b4eaf7239b83fcc3 Author: Svyatoslav Ryhel drm/tegra: rgb: Parameterize configuration based on bus flags This commit updates tegra_rgb_encoder_enable() to configure pixel clock polarity, display enable polarity, and data alignment in the Tegra display controller registers using bus flags retrieved from the attached bridge sta= te. > diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c > index b6d09a8d8e5ea..da9e37fe36689 100644 > --- a/drivers/gpu/drm/tegra/rgb.c > +++ b/drivers/gpu/drm/tegra/rgb.c [ ... ] > @@ -104,14 +105,24 @@ static void tegra_rgb_encoder_enable(struct drm_enc= oder *encoder) > struct drm_display_mode *mode =3D &encoder->crtc->state->adjusted_mode; > struct tegra_output *output =3D encoder_to_output(encoder); > struct tegra_rgb *rgb =3D to_rgb(output); > - u32 value; > + struct drm_bridge_state *bridge_state; > + u32 bus_flags, value; > + > + /* Get but flags from the bridge state. */ > + bridge_state =3D drm_bridge_get_current_state(output->bridge); > + if (bridge_state) > + bus_flags =3D bridge_state->input_bus_cfg.flags; > + else > + bus_flags =3D DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE | > + DRM_BUS_FLAG_DE_HIGH | > + DRM_BUS_FLAG_DATA_MSB_TO_LSB; [Severity: High] Does calling drm_bridge_get_current_state(output->bridge) from tegra_rgb_encoder_enable() in drivers/gpu/drm/tegra/rgb.c access the bridge state without holding output->bridge->base.lock? Looking at drm_bridge_get_current_state(), it asserts that bridge->base.lock is held before reading bridge->base.state: include/drm/drm_bridge.h:drm_bridge_get_current_state() { if (!bridge) return NULL; drm_modeset_lock_assert_held(&bridge->base.lock); if (!bridge->base.state) return NULL; return drm_priv_to_bridge_state(bridge->base.state); } There appear to be two paths where output->bridge->base.lock is not held wh= en tegra_rgb_encoder_enable() runs: 1. Non-blocking atomic modeset commits (DRM_IOCTL_MODE_ATOMIC with DRM_MODE_ATOMIC_NONBLOCK | DRM_MODE_ATOMIC_ALLOW_MODESET): tegra_drm_mode_config_funcs.atomic_commit uses drm_atomic_helper_commit() in drivers/gpu/drm/drm_atomic_helper.c, which swaps state via drm_atomic_helper_swap_state() and schedules state->commit_work onto system_dfl_wq, after which drm_mode_atomic_ioctl() in drivers/gpu/drm/drm_atomic_uapi.c immediately drops all acquired modeset locks: drivers/gpu/drm/drm_atomic_helper.c:drm_atomic_helper_commit() { ... drm_atomic_commit_get(state); if (nonblock) queue_work(system_dfl_wq, &state->commit_work); else commit_tail(state, false); ... } drivers/gpu/drm/drm_atomic_uapi.c:drm_mode_atomic_ioctl() { ... drm_modeset_drop_locks(&ctx); drm_modeset_acquire_fini(&ctx); ... } When the system_dfl_wq worker executes commit_tail() -> tegra_atomic_commit_tail() -> drm_atomic_helper_commit_modeset_enables() -> drm_atomic_helper_commit_encoder_bridge_enable() -> tegra_rgb_encoder_enable(), no drm_modeset_lock is held by the worker threa= d. 2. Bridges without .atomic_duplicate_state during synchronous modeset commi= ts: drm_bridge_attach() always initializes bridge->base.lock via drm_atomic_private_obj_init(), but drm_atomic_add_encoder_bridges() skips acquiring bridge->base.lock when the bridge does not implement .atomic_duplicate_state: drivers/gpu/drm/drm_atomic.c:drm_atomic_add_encoder_bridges() { ... drm_for_each_bridge_in_chain(encoder, bridge) { /* Skip bridges that don't implement the atomic state hooks. */ if (!bridge->funcs->atomic_duplicate_state) continue; bridge_state =3D drm_atomic_get_bridge_state(state, bridge); ... } In both cases, calling drm_bridge_get_current_state(output->bridge) trigger= s a lockdep warning on drm_modeset_lock_assert_held(&bridge->base.lock) under CONFIG_PROVE_LOCKING and reads output->bridge->base.state without holding bridge->base.lock. Should tegra_rgb_encoder_helper_funcs implement .atomic_enable() instead of .enable() and look up the bridge state from the atomic state via drm_atomic_get_new_bridge_state(state, output->bridge)? [ ... ] --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261022132259.2407= 17-1-clamor95@gmail.com?part=3D5