[RFC PATCH v1] drm: rockchip: add drm_plane_create_blend_mode_property

[Andy Yan]

Helllo，

At 2026-08-24 05:06:45, "Johan Jonker" <jbx6244 at gmail.com> wrote:
>
>
>On 8/23/26 21:19, Heiko Stübner wrote:
>> Hi Johan,
>> 
>> Am Sonntag, 23. August 2026, 14:29:09 Mitteleuropäische Sommerzeit schrieb Johan Jonker:
>>> A validate_blend_mode_for_alpha_formats() function was added that
>>> fills the kernel log with warnings for Rockchip VOP version 1 SoCs.
>>> Add a drm_plane_create_blend_mode_property() function as fix.
>> 
>
>> This is missing explanation on why PIXEL_NONE is the correct value.
>> 
>> VOP2 seems to support all 3 blend modes? So a sentece explaining
>> the pixel_none value would be helpful.
>> 
>> 
>
>Hi,
>
>In the vop_plane_atomic_update() function there's a comment with win0 blend broken:
>
>	/*
>	 * Blending win0 with the background color doesn't seem to work
>	 * correctly. We only get the background color, no matter the contents
>	 * of the win0 framebuffer.  However, blending pre-multiplied color
>	 * with the default opaque black default background color is a no-op,
>	 * so we can just disable blending to get the correct result.
>	 */
>

     All VOP 1 do not support alpha blending with background.
    Also, some VOPs do not support alpha when scaling is enabled, except those marked with VOP_FEATURE_ALPHA_SCALE， see[0]

[0]https://github.com/rockchip-linux/kernel/blob/develop-6.12/drivers/gpu/drm/rockchip/rockchip_vop_reg.c

>In the function vop2_plane_init() there are these blends: 
>
>	unsigned int blend_caps = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
>				  BIT(DRM_MODE_BLEND_PREMULTI) |
>				  BIT(DRM_MODE_BLEND_COVERAGE);
>
>My question:
>Could someone with more know-how tell us what VOP version 1 is capable of?
>Is there anything that needs to be set like in other drivers?
>
>For example:
>		switch (pixel_blend_mode) {
>		case DRM_MODE_BLEND_PREMULTI:
>			break;
>		case DRM_MODE_BLEND_COVERAGE:
>			break;
>		case DRM_MODE_BLEND_PIXEL_NONE:
>		default:
>			break;
>		}
>
>If someone comes up with another solution/patch that's also fine, as long the kernel warnings are gone.
>
>Thanks!
>
>Johan
>
>
>
>> Heiko
>> 
>>> Signed-off-by: Johan Jonker <jbx6244 at gmail.com>
>>> ---
>>>
>>> https://lore.kernel.org/all/20260526181700.25310-3-leandro.ribeiro@collabora.com/
>>> ---
>>>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>> index 0090d8ff0c79..0bc5b606f021 100644
>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>>> @@ -1850,6 +1850,8 @@ static void vop_plane_add_properties(struct drm_plane *plane,
>>>  	if (flags)
>>>  		drm_plane_create_rotation_property(plane, DRM_MODE_ROTATE_0,
>>>  						   DRM_MODE_ROTATE_0 | flags);
>>> +	drm_plane_create_blend_mode_property(plane,
>>> +					     BIT(DRM_MODE_BLEND_PIXEL_NONE));
>>>  }
>>>  
>>>  static int vop_create_crtc(struct vop *vop)
>>>
>> 
>> 
>> 
>> 
>