Partially revert "video: fbdev: amba-clcd: Retire elder CLCD driver"

Also partially revert the follow-up change "drm: pl111: Absorb the
external register header".

This reverts the parts of commits
7e4e589 and
0fb8125 that touch paths outside
of drivers/gpu/drm/pl111.

The fbdev driver is used by Android's FVP configuration. Using the
DRM driver together with DRM's fbdev emulation results in a failure
to boot Android. The root cause is that Android's generic fbdev
userspace driver relies on the ability to set the pixel format via
FBIOPUT_VSCREENINFO, which is not supported by fbdev emulation.

There have been other less critical behavioral differences identified
between the fbdev driver and the DRM driver with fbdev emulation. The
DRM driver exposes different values for the panel's width, height and
refresh rate, and the DRM driver fails a FBIOPUT_VSCREENINFO syscall
with yres_virtual greater than the maximum supported value instead
of letting the syscall succeed and setting yres_virtual based on yres.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200929195344.2219796-1-pcc@google.com

Author: pcc

MAINTAINERS

@@ -1460,6 +1460,11 @@ S:	Odd Fixes
 F:	drivers/amba/
 F:	include/linux/amba/bus.h
 
+ARM PRIMECELL CLCD PL110 DRIVER
+M:	Russell King <linux@armlinux.org.uk>
+S:	Odd Fixes
+F:	drivers/video/fbdev/amba-clcd.*
+
 ARM PRIMECELL KMI PL050 DRIVER
 M:	Russell King <linux@armlinux.org.uk>
 S:	Odd Fixes

drivers/video/fbdev/Kconfig

@@ -272,6 +272,26 @@ config FB_PM2_FIFO_DISCONNECT
 	help
 	  Support the Permedia2 FIFO disconnect feature.
 
+config FB_ARMCLCD
+	tristate "ARM PrimeCell PL110 support"
+	depends on ARM || ARM64 || COMPILE_TEST
+	depends on FB && ARM_AMBA && HAS_IOMEM
+	select FB_CFB_FILLRECT
+	select FB_CFB_COPYAREA
+	select FB_CFB_IMAGEBLIT
+	select FB_MODE_HELPERS if OF
+	select VIDEOMODE_HELPERS if OF
+	select BACKLIGHT_CLASS_DEVICE if OF
+	help
+	  This framebuffer device driver is for the ARM PrimeCell PL110
+	  Colour LCD controller.  ARM PrimeCells provide the building
+	  blocks for System on a Chip devices.
+
+	  If you want to compile this as a module (=code which can be
+	  inserted into and removed from the running kernel), say M
+	  here and read <file:Documentation/kbuild/modules.rst>.  The module
+	  will be called amba-clcd.
+
 config FB_ACORN
 	bool "Acorn VIDC support"
 	depends on (FB = y) && ARM && ARCH_ACORN

drivers/video/fbdev/Makefile

@@ -75,6 +75,7 @@ obj-$(CONFIG_FB_HIT)              += hitfb.o
 obj-$(CONFIG_FB_ATMEL)		  += atmel_lcdfb.o
 obj-$(CONFIG_FB_PVR2)             += pvr2fb.o
 obj-$(CONFIG_FB_VOODOO1)          += sstfb.o
+obj-$(CONFIG_FB_ARMCLCD)	  += amba-clcd.o
 obj-$(CONFIG_FB_GOLDFISH)         += goldfishfb.o
 obj-$(CONFIG_FB_68328)            += 68328fb.o
 obj-$(CONFIG_FB_GBE)              += gbefb.o