Hi, On Mon, Apr 25, 2022 at 10:56 PM Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> wrote: > > Current DP driver implementation has adding safe mode done at > dp_hpd_plug_handle() which is expected to be executed under event > thread context. > > However there is possible circular locking happen (see blow stack trace) > after edp driver call dp_hpd_plug_handle() from dp_bridge_enable() which > is executed under drm_thread context. > > After review all possibilities methods and as discussed on > https://patchwork.freedesktop.org/patch/483155/, supporting EDID > compliance tests in the driver is quite hacky. As seen with other > vendor drivers, supporting these will be much easier with IGT. Hence > removing all the related fail safe code for it so that no possibility > of circular lock will happen. > > ====================================================== > WARNING: possible circular locking dependency detected > 5.15.35-lockdep #6 Tainted: G W > ------------------------------------------------------ > frecon/429 is trying to acquire lock: > ffffff808dc3c4e8 (&dev->mode_config.mutex){+.+.}-{3:3}, at: > dp_panel_add_fail_safe_mode+0x4c/0xa0 > > but task is already holding lock: > ffffff808dc441e0 (&kms->commit_lock[i]){+.+.}-{3:3}, at: lock_crtcs+0xb4/0x124 > > which lock already depends on the new lock. > > the existing dependency chain (in reverse order) is: > > -> #3 (&kms->commit_lock[i]){+.+.}-{3:3}: > __mutex_lock_common+0x174/0x1a64 > mutex_lock_nested+0x98/0xac > lock_crtcs+0xb4/0x124 > msm_atomic_commit_tail+0x330/0x748 > commit_tail+0x19c/0x278 > drm_atomic_helper_commit+0x1dc/0x1f0 > drm_atomic_commit+0xc0/0xd8 > drm_atomic_helper_set_config+0xb4/0x134 > drm_mode_setcrtc+0x688/0x1248 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > -> #2 (crtc_ww_class_mutex){+.+.}-{3:3}: > __mutex_lock_common+0x174/0x1a64 > ww_mutex_lock+0xb8/0x278 > modeset_lock+0x304/0x4ac > drm_modeset_lock+0x4c/0x7c > drmm_mode_config_init+0x4a8/0xc50 > msm_drm_init+0x274/0xac0 > msm_drm_bind+0x20/0x2c > try_to_bring_up_master+0x3dc/0x470 > __component_add+0x18c/0x3c0 > component_add+0x1c/0x28 > dp_display_probe+0x954/0xa98 > platform_probe+0x124/0x15c > really_probe+0x1b0/0x5f8 > __driver_probe_device+0x174/0x20c > driver_probe_device+0x70/0x134 > __device_attach_driver+0x130/0x1d0 > bus_for_each_drv+0xfc/0x14c > __device_attach+0x1bc/0x2bc > device_initial_probe+0x1c/0x28 > bus_probe_device+0x94/0x178 > deferred_probe_work_func+0x1a4/0x1f0 > process_one_work+0x5d4/0x9dc > worker_thread+0x898/0xccc > kthread+0x2d4/0x3d4 > ret_from_fork+0x10/0x20 > > -> #1 (crtc_ww_class_acquire){+.+.}-{0:0}: > ww_acquire_init+0x1c4/0x2c8 > drm_modeset_acquire_init+0x44/0xc8 > drm_helper_probe_single_connector_modes+0xb0/0x12dc > drm_mode_getconnector+0x5dc/0xfe8 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > -> #0 (&dev->mode_config.mutex){+.+.}-{3:3}: > __lock_acquire+0x2650/0x672c > lock_acquire+0x1b4/0x4ac > __mutex_lock_common+0x174/0x1a64 > mutex_lock_nested+0x98/0xac > dp_panel_add_fail_safe_mode+0x4c/0xa0 > dp_hpd_plug_handle+0x1f0/0x280 > dp_bridge_enable+0x94/0x2b8 > drm_atomic_bridge_chain_enable+0x11c/0x168 > drm_atomic_helper_commit_modeset_enables+0x500/0x740 > msm_atomic_commit_tail+0x3e4/0x748 > commit_tail+0x19c/0x278 > drm_atomic_helper_commit+0x1dc/0x1f0 > drm_atomic_commit+0xc0/0xd8 > drm_atomic_helper_set_config+0xb4/0x134 > drm_mode_setcrtc+0x688/0x1248 > drm_ioctl_kernel+0x1e4/0x338 > drm_ioctl+0x3a4/0x684 > __arm64_sys_ioctl+0x118/0x154 > invoke_syscall+0x78/0x224 > el0_svc_common+0x178/0x200 > do_el0_svc+0x94/0x13c > el0_svc+0x5c/0xec > el0t_64_sync_handler+0x78/0x108 > el0t_64_sync+0x1a4/0x1a8 > > Changes in v2: > -- re text commit title > -- remove all fail safe mode > > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx> Reported-by: Douglas Anderson <dianders@xxxxxxxxxxxx> Fixes: f1b47e6a8df8 ("drm/msm/dp: remove fail safe mode related code") > @@ -151,15 +151,6 @@ static int dp_panel_update_modes(struct drm_connector *connector, > return rc; > } > > -void dp_panel_add_fail_safe_mode(struct drm_connector *connector) > -{ > - /* fail safe edid */ > - mutex_lock(&connector->dev->mode_config.mutex); > - if (drm_add_modes_noedid(connector, 640, 480)) > - drm_set_preferred_mode(connector, 640, 480); > - mutex_unlock(&connector->dev->mode_config.mutex); > -} You removed this function but you forgot to remove it from the header in "drivers/gpu/drm/msm/dp/dp_panel.h" -Doug
