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_enable() --
commit 743a0ce150c28976e990ee80b4eaf7239b83fcc3 Author: Svyatoslav Ryhel <[email protected]> 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 state. > 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_encoder > *encoder) > struct drm_display_mode *mode = &encoder->crtc->state->adjusted_mode; > struct tegra_output *output = encoder_to_output(encoder); > struct tegra_rgb *rgb = to_rgb(output); > - u32 value; > + struct drm_bridge_state *bridge_state; > + u32 bus_flags, value; > + > + /* Get but flags from the bridge state. */ > + bridge_state = drm_bridge_get_current_state(output->bridge); > + if (bridge_state) > + bus_flags = bridge_state->input_bus_cfg.flags; > + else > + bus_flags = 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 when 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 thread. 2. Bridges without .atomic_duplicate_state during synchronous modeset commits: 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 = drm_atomic_get_bridge_state(state, bridge); ... } In both cases, calling drm_bridge_get_current_state(output->bridge) triggers 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)? [ ... ] -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=5
