dm: syscon: Add support for of-platdata

Provide a new function which can cope with obtaining information from
of-platdata instead of the device tree.

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

drivers/core/syscon-uclass.c

@@ -29,7 +29,20 @@ static int syscon_pre_probe(struct udevice *dev)
 {
 	struct syscon_uc_info *priv = dev_get_uclass_priv(dev);
 
+	/*
+	 * With OF_PLATDATA we really have no way of knowing the format of
+	 * the device-specific platform data. So we assume that it starts with
+	 * a 'reg' member, and this holds a single address and size. Drivers
+	 * using OF_PLATDATA will need to ensure that this is true.
+	 */
+#if CONFIG_IS_ENABLED(OF_PLATDATA)
+	struct syscon_base_platdata *plat = dev_get_platdata(dev);
+
+	return regmap_init_mem_platdata(dev, plat->reg, ARRAY_SIZE(plat->reg),
+					&priv->regmap);
+#else
 	return regmap_init_mem(dev, &priv->regmap);
+#endif
 }
 
 int syscon_get_by_driver_data(ulong driver_data, struct udevice **devp)

include/syscon.h

@@ -23,6 +23,17 @@ struct syscon_ops {
 
 #define syscon_get_ops(dev)        ((struct syscon_ops *)(dev)->driver->ops)
 
+#if CONFIG_IS_ENABLED(OF_PLATDATA)
+/*
+ * We don't support 64-bit machines. If they are so resource-contrained that
+ * they need to use OF_PLATDATA, something is horribly wrong with the
+ * education of our hardware engineers.
+ */
+struct syscon_base_platdata {
+	u32 reg[2];
+};
+#endif
+
 /**
  * syscon_get_regmap() - Get access to a register map
  *