[PATCH V3] drm/loongson: Create blend mode property for cursor plane

[PATCH V3] drm/loongson: Create blend mode property for cursor plane

[Huacai Chen]

After commit 860e748bddcc929 ("drm: ensure blend mode supported if pixel
format with alpha exposed") we get warnings at boot:

loongson 0000:00:06.1: [drm] [PLANE:41:ls-cursor-plane-0] pixel format with alpha exposed but blend mode not setup. Please fix.
loongson 0000:00:06.1: [drm] [PLANE:46:ls-cursor-plane-1] pixel format with alpha exposed but blend mode not setup. Please fix.

The reason is the cursor plane supports color formats with alpha but the
driver doesn't create blend mode property, which triggers the warning in
validate_blend_mode_for_alpha_formats().

The loongson DC HW doesn't support DRM_MODE_BLEND_PREMULTI, so create
blend mode property with DRM_MODE_BLEND_COVERAGE for cursor planes since
it is the only one implemented in the driver.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/gpu/drm/loongson/lsdc_plane.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c b/drivers/gpu/drm/loongson/lsdc_plane.c
index bea42215796d..bcc0ffa17bdf 100644
--- a/drivers/gpu/drm/loongson/lsdc_plane.c
+++ b/drivers/gpu/drm/loongson/lsdc_plane.c
@@ -7,6 +7,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_blend.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_atomic_helper.h>
 #include <drm/drm_print.h>
@@ -765,7 +766,7 @@ int ls7a1000_cursor_plane_init(struct drm_device *ddev,
 
 	drm_plane_helper_add(plane, &ls7a1000_cursor_plane_helper_funcs);
 
-	return 0;
+	return drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_COVERAGE));
 }
 
 int ls7a2000_cursor_plane_init(struct drm_device *ddev,
@@ -790,5 +791,5 @@ int ls7a2000_cursor_plane_init(struct drm_device *ddev,
 
 	drm_plane_helper_add(plane, &ls7a2000_cursor_plane_helper_funcs);
 
-	return 0;
+	return drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_COVERAGE));
 }
-- 
2.52.0

Re: [PATCH V3] drm/loongson: Create blend mode property for cursor plane

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] State mismatch between blend mode property and atomic state initialization rejects atomic commits.
--

commit e4c1ccbb76c983c05930b35bbb7291c8273016d7
Author: Huacai Chen <chenhuacai@kernel.org>

drm/loongson: Create blend mode property for cursor plane

This commit adds a blend mode property for cursor planes, exposing only
the DRM_MODE_BLEND_COVERAGE mode since the hardware does not support
DRM_MODE_BLEND_PREMULTI.

> diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c b/drivers/gpu/drm/loongson/lsdc_plane.c
> index bea42215796d4..bcc0ffa17bdf2 100644
> --- a/drivers/gpu/drm/loongson/lsdc_plane.c
> +++ b/drivers/gpu/drm/loongson/lsdc_plane.c
[ ... ]
> @@ -765,7 +766,7 @@ int ls7a1000_cursor_plane_init(struct drm_device *ddev,
>  
>  	drm_plane_helper_add(plane, &ls7a1000_cursor_plane_helper_funcs);
>  
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_COVERAGE));
>  }

[Severity: High]
Will this cause atomic commits to fail during modesetting?

This adds a blend mode property supporting only COVERAGE, but the driver's
plane functions use the default reset hook:

drivers/gpu/drm/loongson/lsdc_plane.c:lsdc_plane_funcs {
        ...
        .reset = drm_atomic_helper_plane_reset,
        ...
}

The default drm_atomic_helper_plane_reset() unconditionally initializes
the plane state to PREMULTI.

Because PREMULTI is not registered as a supported enum value in the plane's
blend mode property mask, when compositors query the current properties and
submit them back, validation fails in drm_property_change_valid_get()
returning -EINVAL.

Should the driver provide a custom reset hook that initializes the state to
DRM_MODE_BLEND_COVERAGE instead?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260903084212.3621540-1-chenhuacai@loongson.cn?part=1

Re: [PATCH V3] drm/loongson: Create blend mode property for cursor plane

[Icenowy Zheng]

在 2026-09-03四的 16:42 +0800，Huacai Chen写道：
> After commit 860e748bddcc929 ("drm: ensure blend mode supported if
> pixel
> format with alpha exposed") we get warnings at boot:
> 
> loongson 0000:00:06.1: [drm] [PLANE:41:ls-cursor-plane-0] pixel
> format with alpha exposed but blend mode not setup. Please fix.
> loongson 0000:00:06.1: [drm] [PLANE:46:ls-cursor-plane-1] pixel
> format with alpha exposed but blend mode not setup. Please fix.
> 
> The reason is the cursor plane supports color formats with alpha but
> the
> driver doesn't create blend mode property, which triggers the warning
> in
> validate_blend_mode_for_alpha_formats().
> 
> The loongson DC HW doesn't support DRM_MODE_BLEND_PREMULTI, so create
> blend mode property with DRM_MODE_BLEND_COVERAGE for cursor planes
> since
> it is the only one implemented in the driver.
> 
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Reviewed-by: Icenowy Zheng <zhengxingda@iscas.ac.cn>

Thanks,
Icenowy

> ---
>  drivers/gpu/drm/loongson/lsdc_plane.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c
> b/drivers/gpu/drm/loongson/lsdc_plane.c
> index bea42215796d..bcc0ffa17bdf 100644
> --- a/drivers/gpu/drm/loongson/lsdc_plane.c
> +++ b/drivers/gpu/drm/loongson/lsdc_plane.c
> @@ -7,6 +7,7 @@
>  
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_blend.h>
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_gem_atomic_helper.h>
>  #include <drm/drm_print.h>
> @@ -765,7 +766,7 @@ int ls7a1000_cursor_plane_init(struct drm_device
> *ddev,
>  
>  	drm_plane_helper_add(plane,
> &ls7a1000_cursor_plane_helper_funcs);
>  
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane,
> BIT(DRM_MODE_BLEND_COVERAGE));
>  }
>  
>  int ls7a2000_cursor_plane_init(struct drm_device *ddev,
> @@ -790,5 +791,5 @@ int ls7a2000_cursor_plane_init(struct drm_device
> *ddev,
>  
>  	drm_plane_helper_add(plane,
> &ls7a2000_cursor_plane_helper_funcs);
>  
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane,
> BIT(DRM_MODE_BLEND_COVERAGE));
>  }

Re: [PATCH V3] drm/loongson: Create blend mode property for cursor plane

[Jianmin Lv]

On 2026/9/3 下午4:42, Huacai Chen wrote:
> After commit 860e748bddcc929 ("drm: ensure blend mode supported if pixel
> format with alpha exposed") we get warnings at boot:
> 
> loongson 0000:00:06.1: [drm] [PLANE:41:ls-cursor-plane-0] pixel format with alpha exposed but blend mode not setup. Please fix.
> loongson 0000:00:06.1: [drm] [PLANE:46:ls-cursor-plane-1] pixel format with alpha exposed but blend mode not setup. Please fix.
> 
> The reason is the cursor plane supports color formats with alpha but the
> driver doesn't create blend mode property, which triggers the warning in
> validate_blend_mode_for_alpha_formats().
> 
> The loongson DC HW doesn't support DRM_MODE_BLEND_PREMULTI, so create
> blend mode property with DRM_MODE_BLEND_COVERAGE for cursor planes since
> it is the only one implemented in the driver.
> 
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
Reviewed-by: Jianmin Lv <lvjianmin@loongson.cn>

>   drivers/gpu/drm/loongson/lsdc_plane.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c b/drivers/gpu/drm/loongson/lsdc_plane.c
> index bea42215796d..bcc0ffa17bdf 100644
> --- a/drivers/gpu/drm/loongson/lsdc_plane.c
> +++ b/drivers/gpu/drm/loongson/lsdc_plane.c
> @@ -7,6 +7,7 @@
>   
>   #include <drm/drm_atomic.h>
>   #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_blend.h>
>   #include <drm/drm_framebuffer.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_print.h>
> @@ -765,7 +766,7 @@ int ls7a1000_cursor_plane_init(struct drm_device *ddev,
>   
>   	drm_plane_helper_add(plane, &ls7a1000_cursor_plane_helper_funcs);
>   
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_COVERAGE));
>   }
>   
>   int ls7a2000_cursor_plane_init(struct drm_device *ddev,
> @@ -790,5 +791,5 @@ int ls7a2000_cursor_plane_init(struct drm_device *ddev,
>   
>   	drm_plane_helper_add(plane, &ls7a2000_cursor_plane_helper_funcs);
>   
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_COVERAGE));
>   }
> 

Re: [PATCH V3] drm/loongson: Create blend mode property for cursor plane

[Icenowy Zheng]

在 2026-09-03四的 16:42 +0800，Huacai Chen写道：
> After commit 860e748bddcc929 ("drm: ensure blend mode supported if
> pixel
> format with alpha exposed") we get warnings at boot:
> 
> loongson 0000:00:06.1: [drm] [PLANE:41:ls-cursor-plane-0] pixel
> format with alpha exposed but blend mode not setup. Please fix.
> loongson 0000:00:06.1: [drm] [PLANE:46:ls-cursor-plane-1] pixel
> format with alpha exposed but blend mode not setup. Please fix.
> 
> The reason is the cursor plane supports color formats with alpha but
> the
> driver doesn't create blend mode property, which triggers the warning
> in
> validate_blend_mode_for_alpha_formats().
> 
> The loongson DC HW doesn't support DRM_MODE_BLEND_PREMULTI, so create
> blend mode property with DRM_MODE_BLEND_COVERAGE for cursor planes
> since
> it is the only one implemented in the driver.

It looks like this patch is hanging here for weeks. Should I apply it
to drm-misc-fixes?

Thanks,
Icenowy

> 
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
>  drivers/gpu/drm/loongson/lsdc_plane.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c
> b/drivers/gpu/drm/loongson/lsdc_plane.c
> index bea42215796d..bcc0ffa17bdf 100644
> --- a/drivers/gpu/drm/loongson/lsdc_plane.c
> +++ b/drivers/gpu/drm/loongson/lsdc_plane.c
> @@ -7,6 +7,7 @@
>  
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_blend.h>
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_gem_atomic_helper.h>
>  #include <drm/drm_print.h>
> @@ -765,7 +766,7 @@ int ls7a1000_cursor_plane_init(struct drm_device
> *ddev,
>  
>  	drm_plane_helper_add(plane,
> &ls7a1000_cursor_plane_helper_funcs);
>  
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane,
> BIT(DRM_MODE_BLEND_COVERAGE));
>  }
>  
>  int ls7a2000_cursor_plane_init(struct drm_device *ddev,
> @@ -790,5 +791,5 @@ int ls7a2000_cursor_plane_init(struct drm_device
> *ddev,
>  
>  	drm_plane_helper_add(plane,
> &ls7a2000_cursor_plane_helper_funcs);
>  
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane,
> BIT(DRM_MODE_BLEND_COVERAGE));
>  }

Re: [PATCH V3] drm/loongson: Create blend mode property for cursor plane

[Thomas Zimmermann]

Am 17.09.26 um 07:08 schrieb Icenowy Zheng:
> 在 2026-09-03四的 16:42 +0800，Huacai Chen写道：
>> After commit 860e748bddcc929 ("drm: ensure blend mode supported if
>> pixel
>> format with alpha exposed") we get warnings at boot:
>>
>> loongson 0000:00:06.1: [drm] [PLANE:41:ls-cursor-plane-0] pixel
>> format with alpha exposed but blend mode not setup. Please fix.
>> loongson 0000:00:06.1: [drm] [PLANE:46:ls-cursor-plane-1] pixel
>> format with alpha exposed but blend mode not setup. Please fix.
>>
>> The reason is the cursor plane supports color formats with alpha but
>> the
>> driver doesn't create blend mode property, which triggers the warning
>> in
>> validate_blend_mode_for_alpha_formats().
>>
>> The loongson DC HW doesn't support DRM_MODE_BLEND_PREMULTI, so create
>> blend mode property with DRM_MODE_BLEND_COVERAGE for cursor planes
>> since
>> it is the only one implemented in the driver.
> It looks like this patch is hanging here for weeks. Should I apply it
> to drm-misc-fixes?

Go ahead

>
> Thanks,
> Icenowy
>
>> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
>> ---
>>   drivers/gpu/drm/loongson/lsdc_plane.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c
>> b/drivers/gpu/drm/loongson/lsdc_plane.c
>> index bea42215796d..bcc0ffa17bdf 100644
>> --- a/drivers/gpu/drm/loongson/lsdc_plane.c
>> +++ b/drivers/gpu/drm/loongson/lsdc_plane.c
>> @@ -7,6 +7,7 @@
>>   
>>   #include <drm/drm_atomic.h>
>>   #include <drm/drm_atomic_helper.h>
>> +#include <drm/drm_blend.h>
>>   #include <drm/drm_framebuffer.h>
>>   #include <drm/drm_gem_atomic_helper.h>
>>   #include <drm/drm_print.h>
>> @@ -765,7 +766,7 @@ int ls7a1000_cursor_plane_init(struct drm_device
>> *ddev,
>>   
>>   	drm_plane_helper_add(plane,
>> &ls7a1000_cursor_plane_helper_funcs);
>>   
>> -	return 0;
>> +	return drm_plane_create_blend_mode_property(plane,
>> BIT(DRM_MODE_BLEND_COVERAGE));
>>   }
>>   
>>   int ls7a2000_cursor_plane_init(struct drm_device *ddev,
>> @@ -790,5 +791,5 @@ int ls7a2000_cursor_plane_init(struct drm_device
>> *ddev,
>>   
>>   	drm_plane_helper_add(plane,
>> &ls7a2000_cursor_plane_helper_funcs);
>>   
>> -	return 0;
>> +	return drm_plane_create_blend_mode_property(plane,
>> BIT(DRM_MODE_BLEND_COVERAGE));
>>   }

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)

Re: [PATCH V3] drm/loongson: Create blend mode property for cursor plane

[Icenowy Zheng]

在 2026-09-03四的 16:42 +0800，Huacai Chen写道：
> After commit 860e748bddcc929 ("drm: ensure blend mode supported if
> pixel
> format with alpha exposed") we get warnings at boot:
> 
> loongson 0000:00:06.1: [drm] [PLANE:41:ls-cursor-plane-0] pixel
> format with alpha exposed but blend mode not setup. Please fix.
> loongson 0000:00:06.1: [drm] [PLANE:46:ls-cursor-plane-1] pixel
> format with alpha exposed but blend mode not setup. Please fix.
> 
> The reason is the cursor plane supports color formats with alpha but
> the
> driver doesn't create blend mode property, which triggers the warning
> in
> validate_blend_mode_for_alpha_formats().
> 
> The loongson DC HW doesn't support DRM_MODE_BLEND_PREMULTI, so create
> blend mode property with DRM_MODE_BLEND_COVERAGE for cursor planes
> since
> it is the only one implemented in the driver.
> 
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Applied to drm-misc-fixes.

Thanks,
Icenowy

> ---
>  drivers/gpu/drm/loongson/lsdc_plane.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/loongson/lsdc_plane.c
> b/drivers/gpu/drm/loongson/lsdc_plane.c
> index bea42215796d..bcc0ffa17bdf 100644
> --- a/drivers/gpu/drm/loongson/lsdc_plane.c
> +++ b/drivers/gpu/drm/loongson/lsdc_plane.c
> @@ -7,6 +7,7 @@
>  
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_blend.h>
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_gem_atomic_helper.h>
>  #include <drm/drm_print.h>
> @@ -765,7 +766,7 @@ int ls7a1000_cursor_plane_init(struct drm_device
> *ddev,
>  
>  	drm_plane_helper_add(plane,
> &ls7a1000_cursor_plane_helper_funcs);
>  
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane,
> BIT(DRM_MODE_BLEND_COVERAGE));
>  }
>  
>  int ls7a2000_cursor_plane_init(struct drm_device *ddev,
> @@ -790,5 +791,5 @@ int ls7a2000_cursor_plane_init(struct drm_device
> *ddev,
>  
>  	drm_plane_helper_add(plane,
> &ls7a2000_cursor_plane_helper_funcs);
>  
> -	return 0;
> +	return drm_plane_create_blend_mode_property(plane,
> BIT(DRM_MODE_BLEND_COVERAGE));
>  }