dm: core: Add an option to support SPL in read-only memory

Some systems (e.g. x86 APL) run SPL from read-only memory. The device
instances created by dtoc are therefore not writeable. To make things work
we would need to copy the devices to read/write memory.

To avoid this, add an option to use a separate runtime struct for devices,
just as is done for drivers. This can be used to hold information that
changes at runtime, avoiding the need for a copy.

Also add a Kconfig option for read-only SPL, which selects this feature.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

dts/Kconfig

@@ -380,6 +380,17 @@ config SPL_OF_PLATDATA_NO_BIND
 	  some code space in U-Boot. This can be disabled if binding is needed,
 	  at the code of some code size increase.
 
+config SPL_OF_PLATDATA_RT
+	bool "Use a separate struct for device runtime data"
+	depends on SPL_OF_PLATDATA_INST
+	default y
+	help
+	  For systems running SPL from read-only memory it is convenient to
+	  separate out the runtime information, so that the devices don't need
+	  to be copied before being used. This moves the read-write parts of
+	  struct udevice (at present just the flags) into a separate struct,
+	  which is allocated at runtime.
+
 endif
 
 config TPL_OF_PLATDATA
@@ -429,6 +440,17 @@ config TPL_OF_PLATDATA_NO_BIND
 	  some code space in U-Boot. This can be disabled if binding is needed,
 	  at the code of some code size increase.
 
+config TPL_OF_PLATDATA_RT
+	bool "Use a separate struct for device runtime data"
+	depends on TPL_OF_PLATDATA_INST
+	default y
+	help
+	  For systems running TPL from read-only memory it is convenient to
+	  separate out the runtime information, so that the devices don't need
+	  to be copied before being used. This moves the read-write parts of
+	  struct udevice (at present just the flags) into a separate struct,
+	  which is allocated at runtime.
+
 endif
 
 endmenu