drm/mediatek: Remove all conflicting aperture devices during probe

If a device has a framebuffer available it might be already used as
display by simple-framebuffer or simpledrm when mediatek-drm is probed.
This is actually helpful when porting to a new device as
framebuffers are simple to setup in device trees and fbcon can be
used to monitor the kernel boot process.

When drm-mediatek loads a new fb device is initialized, however
fbcon remains attached to the initial framebuffer which is no longer
connected to the actual display - the early fb is never removed.

We can gracefully transition from framebuffer handling to drm-managed
display by calling aperture_remove_all_conflicting_devices before
registering mediatek-drm. This takes care of unloading other fb
devices/drivers and disconnects fbcon which then automatically
reconnects to mediatekdrmfb as soon as it's available.

The function is invoked just before drm_dev_register() to kick out
the existing framebuffer as late as possible to reduce the time the
screen is unresponsive.

Signed-off-by: Luca Leonardo Scorcia <l.scorcia@gmail.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20260212192605.263160-1-l.scorcia@gmail.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_drm_drv.c

@@ -4,6 +4,7 @@
  * Author: YT SHEN <yt.shen@mediatek.com>
  */
 
+#include <linux/aperture.h>
 #include <linux/component.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -670,6 +671,10 @@ static int mtk_drm_bind(struct device *dev)
 	if (ret < 0)
 		goto err_free;
 
+	ret = aperture_remove_all_conflicting_devices(DRIVER_NAME);
+	if (ret < 0)
+		dev_err(dev, "Error %d while removing conflicting aperture devices", ret);
+
 	ret = drm_dev_register(drm, 0);
 	if (ret < 0)
 		goto err_deinit;