drm/omap: dsi: allow DSI commands to be sent early

Panel drivers can send DSI commands in panel's prepare(), which happens
before the bridge's enable() is called. The OMAP DSI driver currently
only sets up the DSI interface at bridge's enable(), so prepare() cannot
be used to send DSI commands.

This patch fixes the issue by making it possible to enable the DSI
interface any time a command is about to be sent. Disabling the
interface is be done via delayed work.

Clarifications for the delayed disable work and the panel doing DSI
transactions:

bridge_enable: If the disable callback is called just before
bridge_enable takes the dsi_bus_lock, no problem, bridge_enable just
enables the interface again. If the callback is ran just after
bridge_enable's dsi_bus_unlock, no problem, dsi->video_enabled == true
so the callback does nothing.

bridge_disable: similar to bridge-enable, the callback won't do anything
if video_enabled == true, and after bridge-disable has turned the video
and the interface off, there's nothing to do for the callback.

omap_dsi_host_detach: this is called when the panel does
mipi_dsi_detach(), and we expect the panel to _not_ do any DSI
transactions after (or during) mipi_dsi_detatch(), so there are no
race conditions.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215104657.802264-85-tomi.valkeinen@ti.com

drm/omap: dsi: remove ulps support

ULPS is a niche power-saving feature which only really affects command
mode panels showing a static picture. I know the ULPS code used to work
very long time ago, but I could not get it working with the current
driver. As the ULPS code is not trivial and includes delayed work (so
lots of chances for race issues), and just keeping DSI video and command
mode panels working has been challenging enough even without ULPS, lets
remove ULPS support.

When the DSI driver works reliably for command and video mode displays,
someone interested can work on ULPS and add it back if the power saving
is substantial enough.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215104657.802264-83-tomi.valkeinen@ti.com

drm/omap: dsi: fix and cleanup ddr_clk_always_on

The driver ignores MIPI_DSI_CLOCK_NON_CONTINUOUS, and always uses
non-continuous clock.

Fix this by using MIPI_DSI_CLOCK_NON_CONTINUOUS and at the same time,
drop ddr_clk_always_on field which seems pretty useless.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215104657.802264-82-tomi.valkeinen@ti.com

drm/omap: dsi: move structs & defines to dsi.h

Move structs and defines to a private dsi.h header file to make dsi.c a
bit easier to navigate. Also move the (now) private structs and defines
from omapdss.h to dsi.h.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215104657.802264-75-tomi.valkeinen@ti.com