of/platform: Disable sysfb if a simple-framebuffer node is found

Some DT platforms use EFI to boot and in this case the EFI Boot Services
may register a EFI_GRAPHICS_OUTPUT_PROTOCOL handle, that will later be
queried by the Linux EFI stub to fill the global struct screen_info data.

The data is used by the Generic System Framebuffers (sysfb) framework to
add a platform device with platform data about the system framebuffer.

But if there is a "simple-framebuffer" node in the DT, the OF core will
also do the same and add another device for the system framebuffer.

This could lead for example, to two platform devices ("simple-framebuffer"
and "efi-framebuffer") to be added and matched with their corresponding
drivers. So both efifb and simpledrm will be probed, leading to following:

[ 0.055752] efifb: framebuffer at 0xbd58dc000, using 16000k, total 16000k
[ 0.055755] efifb: mode is 2560x1600x32, linelength=10240, pages=1
[ 0.055758] efifb: scrolling: redraw
[ 0.055759] efifb: Truecolor: size=2:10:10:10, shift=30:20:10:0
...
[ 3.295896] simple-framebuffer bd58dc000.framebuffer: [drm] *ERROR*
could not acquire memory range [??? 0xffff79f30a29ee40-0x2a5000001a7
flags 0x0]: -16
[ 3.298018] simple-framebuffer: probe of bd58dc000.framebuffer
failed with error -16

To prevent the issue, make the OF core to disable sysfb if there is a node
with a "simple-framebuffer" compatible. That way only this device will be
registered and sysfb would not attempt to register another one using the
screen_info data even if this has been filled.

This seems the correct thing to do in this case because:

a) On a DT platform, the DTB is the single source of truth since is what
describes the hardware topology. Even if EFI Boot Services are used to
boot the machine.

b) The of_platform_default_populate_init() function is called in the
arch_initcall_sync() initcall level while the sysfb_init() function
is called later in the subsys_initcall() initcall level.

Reported-by: Andrew Worsley <[e-mail]>
Closes: https://lore.kernel.org/all/[e-mail]
Signed-off-by: Javier Martinez Canillas <[e-mail]>
Reviewed-by: Thomas Zimmermann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

drivers/of/platform.c

···
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/sysfb.h>
 
 #include "of_private.h"
 
···
 		}
 
 		node = of_get_compatible_child(of_chosen, "simple-framebuffer");
-		of_platform_device_create(node, NULL, NULL);
-		of_node_put(node);
+		if (node) {
+			/*
+			 * Since a "simple-framebuffer" device is already added
+			 * here, disable the Generic System Framebuffers (sysfb)
+			 * to prevent it from registering another device for the
+			 * system framebuffer later (e.g: using the screen_info
+			 * data that may had been filled as well).
+			 *
+			 * This can happen for example on DT systems that do EFI
+			 * booting and may provide a GOP handle to the EFI stub.
+			 */
+			sysfb_disable();
+			of_platform_device_create(node, NULL, NULL);
+			of_node_put(node);
+		}
 
 		/* Populate everything else. */
 		of_platform_default_populate(NULL, NULL, NULL);