drm/bridge: Add Cadence DSI driver

Add a driver for Cadence DPI -> DSI bridge.

This driver only support a subset of Cadence DSI bridge capabilities.

This driver has been tested/debugged in a simulated environment which
explains why some of the features are missing.  Here is a
non-exhaustive list of missing features:
 * burst mode
 * DPHY init/configuration steps
 * support for additional input interfaces (SDI input)

DSI commands and non-burst video mode have been tested.
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Acked-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180421070846.10330-1-boris.brezillon@bootlin.com

drivers/gpu/drm/bridge/Kconfig

@@ -25,6 +25,16 @@ config DRM_ANALOGIX_ANX78XX
 	  the HDMI output of an application processor to MyDP
 	  or DisplayPort.
 
+config DRM_CDNS_DSI
+	tristate "Cadence DPI/DSI bridge"
+	select DRM_KMS_HELPER
+	select DRM_MIPI_DSI
+	select DRM_PANEL_BRIDGE
+	depends on OF
+	help
+	  Support Cadence DPI to DSI bridge. This is an internal
+	  bridge and is meant to be directly embedded in a SoC.
+
 config DRM_DUMB_VGA_DAC
 	tristate "Dumb VGA DAC Bridge support"
 	depends on OF

drivers/gpu/drm/bridge/Makefile

 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
+obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
 obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o
 obj-$(CONFIG_DRM_LVDS_ENCODER) += lvds-encoder.o
 obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o