Re: [PATCH v2] drm/msm: properly add and remove internal bridges

[Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>]

On 4/11/2022 4:49 PM, Dmitry Baryshkov wrote:
> Add calls to drm_bridge_add()/drm_bridge_remove() DRM bridges created by
> the driver. This fixes the following warning.
>
> WARNING: CPU: 0 PID: 1 at kernel/locking/mutex.c:579 __mutex_lock+0x840/0x9f4
> DEBUG_LOCKS_WARN_ON(lock->magic != lock)
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.18.0-rc1-00002-g3054695a0d27-dirty #55
> Hardware name: Generic DT based system
>   unwind_backtrace from show_stack+0x10/0x14
>   show_stack from dump_stack_lvl+0x58/0x70
>   dump_stack_lvl from __warn+0xc8/0x1e8
>   __warn from warn_slowpath_fmt+0x78/0xa8
>   warn_slowpath_fmt from __mutex_lock+0x840/0x9f4
>   __mutex_lock from mutex_lock_nested+0x1c/0x24
>   mutex_lock_nested from drm_bridge_hpd_enable+0x2c/0x84
>   drm_bridge_hpd_enable from msm_hdmi_modeset_init+0xc0/0x21c
>   msm_hdmi_modeset_init from mdp4_kms_init+0x53c/0x90c
>   mdp4_kms_init from msm_drm_bind+0x514/0x698
>   msm_drm_bind from try_to_bring_up_aggregate_device+0x160/0x1bc
>   try_to_bring_up_aggregate_device from component_master_add_with_match+0xc4/0xf8
>   component_master_add_with_match from msm_pdev_probe+0x274/0x350
>   msm_pdev_probe from platform_probe+0x5c/0xbc
>   platform_probe from really_probe.part.0+0x9c/0x290
>   really_probe.part.0 from __driver_probe_device+0xa8/0x13c
>   __driver_probe_device from driver_probe_device+0x34/0x10c
>   driver_probe_device from __driver_attach+0xbc/0x178
>   __driver_attach from bus_for_each_dev+0x74/0xc0
>   bus_for_each_dev from bus_add_driver+0x160/0x1e4
>   bus_add_driver from driver_register+0x88/0x118
>   driver_register from do_one_initcall+0x6c/0x334
>   do_one_initcall from kernel_init_freeable+0x1bc/0x220
>   kernel_init_freeable from kernel_init+0x18/0x12c
>   kernel_init from ret_from_fork+0x14/0x2c
>
> Fixes: 3d3f8b1f8b62 ("drm/bridge: make bridge registration independent of drm flow")
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Reviewed-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> ---
> Changes since v1:
>   - Dropped drm_bridge_detach() call, it is not necessary, also it breaks
>     compilation if MSM DRM is built as module.
> ---
>   drivers/gpu/drm/msm/dp/dp_drm.c        | 4 ++++
>   drivers/gpu/drm/msm/dsi/dsi_manager.c  | 3 +++
>   drivers/gpu/drm/msm/hdmi/hdmi_bridge.c | 3 +++
>   drivers/gpu/drm/msm/msm_drv.c          | 3 +++
>   4 files changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_drm.c b/drivers/gpu/drm/msm/dp/dp_drm.c
> index 80f59cf99089..262744914f97 100644
> --- a/drivers/gpu/drm/msm/dp/dp_drm.c
> +++ b/drivers/gpu/drm/msm/dp/dp_drm.c
> @@ -230,9 +230,13 @@ struct drm_bridge *msm_dp_bridge_init(struct msm_dp *dp_display, struct drm_devi
>   	bridge->funcs = &dp_bridge_ops;
>   	bridge->encoder = encoder;
>   
> +	drm_bridge_add(bridge);
> +
>   	rc = drm_bridge_attach(encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>   	if (rc) {
>   		DRM_ERROR("failed to attach bridge, rc=%d\n", rc);
> +		drm_bridge_remove(bridge);
> +
>   		return ERR_PTR(rc);
>   	}
>   
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> index 9f6af0f0fe00..1db93e562fe6 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
> @@ -665,6 +665,8 @@ struct drm_bridge *msm_dsi_manager_bridge_init(u8 id)
>   	bridge = &dsi_bridge->base;
>   	bridge->funcs = &dsi_mgr_bridge_funcs;
>   
> +	drm_bridge_add(bridge);
> +
>   	ret = drm_bridge_attach(encoder, bridge, NULL, 0);
>   	if (ret)
>   		goto fail;
> @@ -735,6 +737,7 @@ struct drm_connector *msm_dsi_manager_ext_bridge_init(u8 id)
>   
>   void msm_dsi_manager_bridge_destroy(struct drm_bridge *bridge)
>   {
> +	drm_bridge_remove(bridge);
>   }
>   
>   int msm_dsi_manager_cmd_xfer(int id, const struct mipi_dsi_msg *msg)
> diff --git a/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c b/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c
> index 10ebe2089cb6..97c24010c4d1 100644
> --- a/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c
> +++ b/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c
> @@ -15,6 +15,7 @@ void msm_hdmi_bridge_destroy(struct drm_bridge *bridge)
>   	struct hdmi_bridge *hdmi_bridge = to_hdmi_bridge(bridge);
>   
>   	msm_hdmi_hpd_disable(hdmi_bridge);
> +	drm_bridge_remove(bridge);
>   }
>   
>   static void msm_hdmi_power_on(struct drm_bridge *bridge)
> @@ -349,6 +350,8 @@ struct drm_bridge *msm_hdmi_bridge_init(struct hdmi *hdmi)
>   		DRM_BRIDGE_OP_DETECT |
>   		DRM_BRIDGE_OP_EDID;
>   
> +	drm_bridge_add(bridge);
> +
>   	ret = drm_bridge_attach(hdmi->encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>   	if (ret)
>   		goto fail;
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 2905b82a9de3..d8f2c8838a7f 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -232,6 +232,9 @@ static int msm_drm_uninit(struct device *dev)
>   
>   	drm_mode_config_cleanup(ddev);
>   
> +	for (i = 0; i < priv->num_bridges; i++)
> +		drm_bridge_remove(priv->bridges[i]);
> +
>   	pm_runtime_get_sync(dev);
>   	msm_irq_uninstall(ddev);
>   	pm_runtime_put_sync(dev);