Re: [RFC PATCH v1] drm: rockchip: add drm_plane_create_blend_mode_property

[Johan Jonker <jbx6244@gmail.com>]

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.
	 */

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@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)
>>
> 
> 
> 
>