[PATCH v6 2/6] drm: bridge: panel: Reset the connector state pointer

[Marek Szyprowski]

On 03.03.2022 17:36, Jagan Teki wrote:
> Trigger hotplug event with drm_kms_helper_hotplug_event might fail if the
> connector state pointer is NULL.
>
> BUG observed in exynos dsi driver where drm_bridge_attach is trying to register
> a connector in panel_bridge before the hotplug event is triggered,
>
> WARNING: CPU: 1 PID: 1 at drivers/gpu/drm/drm_atomic_state_helper.c:494 drm_atomic_helper_connector_duplicate_state+0x94/0x9c
> Modules linked in:
> CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W 5.16.0-rc1-00009-g704b1dbfa4c2 #11058
> Hardware name: Samsung Exynos (Flattened Device Tree)
> [<c0110b30>] (unwind_backtrace) from [<c010c618>] (show_stack+0x10/0x14)
> [<c010c618>] (show_stack) from [<c0b657d4>] (dump_stack_lvl+0x58/0x70)
> [<c0b657d4>] (dump_stack_lvl) from [<c01261dc>] (__warn+0xd0/0x134)
> [<c01261dc>] (__warn) from [<c0b5f628>] (warn_slowpath_fmt+0x5c/0xb4)
> [<c0b5f628>] (warn_slowpath_fmt) from [<c064bce4>] (drm_atomic_helper_connector_duplicate_state+0x94/0x9c)
> [<c064bce4>] (drm_atomic_helper_connector_duplicate_state) from [<c0666b64>] (drm_atomic_get_connector_state+0xd4/0x190)
> [<c0666b64>] (drm_atomic_get_connector_state) from [<c0667928>] (__drm_atomic_helper_set_config+0x314/0x368)
> [<c0667928>] (__drm_atomic_helper_set_config) from [<c067e628>] (drm_client_modeset_commit_atomic+0x170/0x278)
> [<c067e628>] (drm_client_modeset_commit_atomic) from [<c067e800>] (drm_client_modeset_commit_locked+0x60/0x1c8)
> [<c067e800>] (drm_client_modeset_commit_locked) from [<c067e98c>] (drm_client_modeset_commit+0x24/0x40)
> [<c067e98c>] (drm_client_modeset_commit) from [<c06509c0>] (drm_fb_helper_set_par+0xb8/0xf8)
> [<c06509c0>] (drm_fb_helper_set_par) from [<c05b86d0>] (fbcon_init+0x2c0/0x518)
> [<c05b86d0>] (fbcon_init) from [<c060636c>] (visual_init+0xc0/0x108)
> [<c060636c>] (visual_init) from [<c06085e4>] (do_bind_con_driver+0x1b8/0x3a4)
> [<c06085e4>] (do_bind_con_driver) from [<c0608b40>] (do_take_over_console+0x13c/0x1e8)
> [<c0608b40>] (do_take_over_console) from [<c05b6854>] (do_fbcon_takeover+0x78/0xd8)
> [<c05b6854>] (do_fbcon_takeover) from [<c05b1154>] (register_framebuffer+0x208/0x2e0)
> [<c05b1154>] (register_framebuffer) from [<c064ead0>] (__drm_fb_helper_initial_config_and_unlock+0x400/0x63c)
> [<c064ead0>] (__drm_fb_helper_initial_config_and_unlock) from [<c063a718>] (drm_kms_helper_hotplug_event+0x24/0x30)
> [<c063a718>] (drm_kms_helper_hotplug_event) from [<c068f668>] (exynos_dsi_host_attach+0x174/0x1fc)
> [<c068f668>] (exynos_dsi_host_attach) from [<c0699354>] (s6e8aa0_probe+0x1b4/0x218)
>
> So reset the atomic state for a given connector by freeing the state pointer
> and allocate a new empty state object. This can be done using connector
> funcs->reset helper and has to be done before the hotplug even calls.
>
> This patch calls the connector->funcs->reset in panel_bridge_attach.
>
> Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>

Acked-by: Marek Szyprowski <m.szyprowski at samsung.com>

Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>

> ---
> Changes for v6, v5:
> - none
> Changes for v4:
> - new patch
>
>   drivers/gpu/drm/bridge/panel.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
> index b32295abd9e7..f6eea194482a 100644
> --- a/drivers/gpu/drm/bridge/panel.c
> +++ b/drivers/gpu/drm/bridge/panel.c
> @@ -83,6 +83,9 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
>   	drm_connector_attach_encoder(&panel_bridge->connector,
>   					  bridge->encoder);
>   
> +	if (connector->funcs->reset)
> +		connector->funcs->reset(connector);
> +
>   	return 0;
>   }
>   

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland