[PATCH 03/13] drm/sun4i: vi scaler: Restore opaque alpha in video modes

[Chen-Yu Tsai]

On Tue, Aug 4, 2026 at 12:11 AM Jernej Skrabec <jernej.skrabec at gmail.com> wrote:
>
> The DE3 mixer initialization clears the entire mixer register space. This
> also clears VSU_GLOBAL_ALPHA, despite its hardware reset value being 0xff.
>
> The VI scaler uses Video Normal mode for subsampled YUV formats. In this
> mode, VSU_GLOBAL_ALPHA provides the scaler output alpha. Leaving the
> register at zero causes the scaler to produce fully transparent output.
>
> Set VSU_GLOBAL_ALPHA to 0xff whenever configuring a DE3 or newer VI
> scaler. The register is ignored in UI scaling mode.
>
> Fixes: c50519e6db4d ("drm/sun4i: Add basic support for DE3")
> Signed-off-by: Jernej Skrabec <jernej.skrabec at gmail.com>

Acked-by: Chen-Yu Tsai <wens at kernel.org>

> ---
>  drivers/gpu/drm/sun4i/sun8i_vi_scaler.c | 2 ++
>  drivers/gpu/drm/sun4i/sun8i_vi_scaler.h | 1 +
>  2 files changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c b/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c
> index d4412a62c2f0..a5cc99981006 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c
> +++ b/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c
> @@ -975,6 +975,8 @@ void sun8i_vi_scaler_setup(struct sun8i_layer *layer,
>
>                 regmap_write(layer->regs,
>                              SUN50I_SCALER_VSU_SCALE_MODE(base), val);
> +               regmap_write(layer->regs,
> +                            SUN50I_SCALER_VSU_GLB_ALPHA(base), 0xff);
>         }
>
>         regmap_write(layer->regs,
> diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_scaler.h b/drivers/gpu/drm/sun4i/sun8i_vi_scaler.h
> index 245fe2f431c3..d89c0cbe188d 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_vi_scaler.h
> +++ b/drivers/gpu/drm/sun4i/sun8i_vi_scaler.h
> @@ -36,6 +36,7 @@
>  #define SUN50I_SCALER_VSU_EDSCL_CTRL(base)             ((base) + 0x28)
>  #define SUN50I_SCALER_VSU_ANGLE_THR(base)              ((base) + 0x2c)
>  #define SUN8I_SCALER_VSU_OUTSIZE(base)         ((base) + 0x40)
> +#define SUN50I_SCALER_VSU_GLB_ALPHA(base)      ((base) + 0x44)
>  #define SUN8I_SCALER_VSU_YINSIZE(base)         ((base) + 0x80)
>  #define SUN8I_SCALER_VSU_YHSTEP(base)          ((base) + 0x88)
>  #define SUN8I_SCALER_VSU_YVSTEP(base)          ((base) + 0x8c)
> --
> 2.43.0
>