fbdev/simplefb: Support memory-region property

The simple-framebuffer bindings specify that the "memory-region"
property can be used as an alternative to the "reg" property to define
the framebuffer memory used by the display hardware. Implement support
for this in the simplefb driver.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231101172017.3872242-2-thierry.reding@gmail.com

drivers/video/fbdev/simplefb.c

@@ -21,6 +21,7 @@
 #include <linux/platform_device.h>
 #include <linux/clk.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_clk.h>
 #include <linux/of_platform.h>
 #include <linux/parser.h>
@@ -121,12 +122,13 @@ struct simplefb_params {
 	u32 height;
 	u32 stride;
 	struct simplefb_format *format;
+	struct resource memory;
 };
 
 static int simplefb_parse_dt(struct platform_device *pdev,
 			   struct simplefb_params *params)
 {
-	struct device_node *np = pdev->dev.of_node;
+	struct device_node *np = pdev->dev.of_node, *mem;
 	int ret;
 	const char *format;
 	int i;
@@ -166,6 +168,23 @@ static int simplefb_parse_dt(struct platform_device *pdev,
 		return -EINVAL;
 	}
 
+	mem = of_parse_phandle(np, "memory-region", 0);
+	if (mem) {
+		ret = of_address_to_resource(mem, 0, &params->memory);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "failed to parse memory-region\n");
+			of_node_put(mem);
+			return ret;
+		}
+
+		if (of_property_present(np, "reg"))
+			dev_warn(&pdev->dev, "preferring \"memory-region\" over \"reg\" property\n");
+
+		of_node_put(mem);
+	} else {
+		memset(&params->memory, 0, sizeof(params->memory));
+	}
+
 	return 0;
 }
 
@@ -193,6 +212,8 @@ static int simplefb_parse_pd(struct platform_device *pdev,
 		return -EINVAL;
 	}
 
+	memset(&params->memory, 0, sizeof(params->memory));
+
 	return 0;
 }
 
@@ -431,10 +452,14 @@ static int simplefb_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	if (!res) {
-		dev_err(&pdev->dev, "No memory resource\n");
-		return -EINVAL;
+	if (params.memory.start == 0 && params.memory.end == 0) {
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		if (!res) {
+			dev_err(&pdev->dev, "No memory resource\n");
+			return -EINVAL;
+		}
+	} else {
+		res = &params.memory;
 	}
 
 	mem = request_mem_region(res->start, resource_size(res), "simplefb");