Both locking and especially sequencing of nonblocking commits have
evolved a lot. The details are all there, but I noticed that the big
picture and connections have fallen behind a bit. Apply polish.

Motivated by some review discussions with Thierry.

v2: Review from Thierry
Reviewed-by: Thierry Reding <treding@nvidia.com>
Cc: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191204100011.859468-1-daniel.vetter@ffwll.ch