Il 11/03/22 10:34, Ricardo Cañuelo ha scritto:
When unbinding a DRM master driver there's a race condition that sometimes results in an invalid vm access when userspace (gnome-shell) issues a DRM_IOCTL_MODE_GETCONNECTOR ioctl right after a bridge has been removed from an encoder's bridge chain.
This means that once a bridge has been disabled and gone through ps8640_post_disable(), if ps8640_bridge_get_edid() runs afterwards as a result of that ioctl call it will call drm_bridge_chain_pre_enable() and drm_bridge_chain_post_disable() again in a bridge that has been already detached.
Setting `ps_bridge->pre_enabled = false` at a later stage of the bringdown path and calling drm_bridge_chain_pre_enable() inside ps8640_bridge_get_edid() only if needed avoid this, although a proper subsystem-wide fix would be the proper solution, since the same type of race conditions might happen somewhere else.
Tested on an Acer Chromebook R13 (Elm, MT8173) with Debian Sid.
Signed-off-by: Ricardo Cañuelo ricardo.canuelo@collabora.com
Reviewed-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com
drivers/gpu/drm/bridge/parade-ps8640.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)