of: Create platform devices for OF framebuffers

Create a platform device for each OF-declared framebuffer and have
offb bind to these devices. Allows for real hot-unplugging and other
drivers besides offb.

Originally, offb created framebuffer devices while initializing its
module by parsing the OF device tree. No actual Linux device was set
up. This tied OF framebuffers to offb and makes writing other drivers
for the OF framebuffers complicated. The absence of a Linux device
further prevented real hot-unplugging. Adding a distinct platform
device for each OF framebuffer solves both problems. Specifically, a
DRM driver can now provide graphics output for modern userspace.

Some of the offb init code is now located in the OF initialization.
There's now also an implementation of of_platform_default_populate_init(),
which was missing before. The OF side creates different devices for
either OF display nodes or BootX displays as they require different
handling by the driver. The offb drivers picks up each type of device
and runs the appropriate fbdev initialization.

Tested with OF display nodes on qemu's ppc64le target.

v3:
	* declare variable 'node' with function scope (Rob)
v2:
	* run PPC code as part of existing initialization (Rob)
	* add a few more error warnings (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220419100405.12600-2-tzimmermann@suse.de

1 files changed, 64 insertions, 19 deletions

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index a16b74f32aa9..176ed71d20c0 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -507,7 +507,6 @@ int of_platform_default_populate(struct device_node *root,
 }
 EXPORT_SYMBOL_GPL(of_platform_default_populate);
 
-#ifndef CONFIG_PPC
 static const struct of_device_id reserved_mem_matches[] = {
 	{ .compatible = "qcom,rmtfs-mem" },
 	{ .compatible = "qcom,cmd-db" },
@@ -527,26 +526,73 @@ static int __init of_platform_default_populate_init(void)
 	if (!of_have_populated_dt())
 		return -ENODEV;
 
-	/*
-	 * Handle certain compatibles explicitly, since we don't want to create
-	 * platform_devices for every node in /reserved-memory with a
-	 * "compatible",
-	 */
-	for_each_matching_node(node, reserved_mem_matches)
-		of_platform_device_create(node, NULL, NULL);
+	if (IS_ENABLED(CONFIG_PPC)) {
+		struct device_node *boot_display = NULL;
+		struct platform_device *dev;
+		int ret;
+
+		/* Check if we have a MacOS display without a node spec */
+		if (of_get_property(of_chosen, "linux,bootx-noscreen", NULL)) {
+			/*
+			 * The old code tried to work out which node was the MacOS
+			 * display based on the address. I'm dropping that since the
+			 * lack of a node spec only happens with old BootX versions
+			 * (users can update) and with this code, they'll still get
+			 * a display (just not the palette hacks).
+			 */
+			dev = platform_device_alloc("bootx-noscreen", 0);
+			if (WARN_ON(!dev))
+				return -ENOMEM;
+			ret = platform_device_add(dev);
+			if (WARN_ON(ret)) {
+				platform_device_put(dev);
+				return ret;
+			}
+		}
 
-	node = of_find_node_by_path("/firmware");
-	if (node) {
-		of_platform_populate(node, NULL, NULL, NULL);
-		of_node_put(node);
-	}
+		/*
+		 * For OF framebuffers, first create the device for the boot display,
+		 * then for the other framebuffers. Only fail for the boot display;
+		 * ignore errors for the rest.
+		 */
+		for_each_node_by_type(node, "display") {
+			if (!of_get_property(node, "linux,opened", NULL) ||
+			    !of_get_property(node, "linux,boot-display", NULL))
+				continue;
+			dev = of_platform_device_create(node, "of-display", NULL);
+			if (WARN_ON(!dev))
+				return -ENOMEM;
+			boot_display = node;
+			break;
+		}
+		for_each_node_by_type(node, "display") {
+			if (!of_get_property(node, "linux,opened", NULL) || node == boot_display)
+				continue;
+			of_platform_device_create(node, "of-display", NULL);
+		}
 
-	node = of_get_compatible_child(of_chosen, "simple-framebuffer");
-	of_platform_device_create(node, NULL, NULL);
-	of_node_put(node);
+	} else {
+		/*
+		 * Handle certain compatibles explicitly, since we don't want to create
+		 * platform_devices for every node in /reserved-memory with a
+		 * "compatible",
+		 */
+		for_each_matching_node(node, reserved_mem_matches)
+			of_platform_device_create(node, NULL, NULL);
+
+		node = of_find_node_by_path("/firmware");
+		if (node) {
+			of_platform_populate(node, NULL, NULL, NULL);
+			of_node_put(node);
+		}
 
-	/* Populate everything else. */
-	of_platform_default_populate(NULL, NULL, NULL);
+		node = of_get_compatible_child(of_chosen, "simple-framebuffer");
+		of_platform_device_create(node, NULL, NULL);
+		of_node_put(node);
+
+		/* Populate everything else. */
+		of_platform_default_populate(NULL, NULL, NULL);
+	}
 
 	return 0;
 }
@@ -558,7 +604,6 @@ static int __init of_platform_sync_state_init(void)
 	return 0;
 }
 late_initcall_sync(of_platform_sync_state_init);
-#endif
 
 int of_platform_device_destroy(struct device *dev, void *data)
 {