[v2] drm/mediatek: Remove all conflicting aperture devices during probe

[PATCH v2] drm/mediatek: Remove all conflicting aperture devices during probe

Posted by Luca Leonardo Scorcia 2 months ago

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>
---
v2: Moved the call to aperture_remove_all_conflicting_devices to 
    right before drm_dev_register()

 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index a94c51a83261..02effd9fc698 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/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;
-- 
2.43.0

Re: [PATCH v2] drm/mediatek: Remove all conflicting aperture devices during probe

Posted by Chun-Kuang Hu 3 weeks, 5 days ago

Hi, Luca:

Luca Leonardo Scorcia <l.scorcia@gmail.com> 於 2026年2月12日週四 下午7:26寫道：
>
> 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.

Applied to mediatek-drm-next [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-next

Regards,
Chun-Kuang.

>
> Signed-off-by: Luca Leonardo Scorcia <l.scorcia@gmail.com>
> ---
> v2: Moved the call to aperture_remove_all_conflicting_devices to
>     right before drm_dev_register()
>
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index a94c51a83261..02effd9fc698 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/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;
> --
> 2.43.0
>

Re: [PATCH v2] drm/mediatek: Remove all conflicting aperture devices during probe

Posted by CK Hu (胡俊光) 1 month, 3 weeks ago

On Thu, 2026-02-12 at 19:22 +0000, Luca Leonardo Scorcia wrote:
> External email : Please do not click links or open attachments until you have verified the sender or the content.
> 
> 
> 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.

Reviewed-by: CK Hu <ck.hu@mediatek.com>

> 
> Signed-off-by: Luca Leonardo Scorcia <l.scorcia@gmail.com>
> ---
> v2: Moved the call to aperture_remove_all_conflicting_devices to
>     right before drm_dev_register()
> 
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index a94c51a83261..02effd9fc698 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/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;
> --
> 2.43.0
> 
>