Re: [PATCH 02/13] drm/sun4i: vi scaler: Fix coefficient selection

[Chen-Yu Tsai]

On Tue, Aug 4, 2026 at 12:11 AM Jernej Skrabec <jernej.skrabec@xxxxxxxxx> wrote:
>
> Currently, vertical coefficients are selected based on horizontal
> scaling, which is wrong. Additionally, chroma coefficients should be
> selected based on format subsampling.
>
> Fix all that.
>
> Fixes: b862a648de3b ("drm/sun4i: Add support for HW scaling to DE2")
> Signed-off-by: Jernej Skrabec <jernej.skrabec@xxxxxxxxx>

Reviewed-by: Chen-Yu Tsai <wens@xxxxxxxxxx>


Somehow having the two fixes together made the diff much harder for me
to understand.

> ---
>  drivers/gpu/drm/sun4i/sun8i_vi_scaler.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c b/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c
> index 3dec4eeb1ba2..d4412a62c2f0 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c
> +++ b/drivers/gpu/drm/sun4i/sun8i_vi_scaler.c
> @@ -894,20 +894,26 @@ static void sun8i_vi_scaler_set_coeff(struct regmap *map, u32 base,
>                              lan3coefftab32_left[offset + i]);
>                 regmap_write(map, SUN8I_SCALER_VSU_YHCOEFF1(base, i),
>                              lan3coefftab32_right[offset + i]);
> +       }
> +       offset = sun8i_vi_scaler_coef_index(vstep) *
> +                       SUN8I_VI_SCALER_COEFF_COUNT;
> +       for (i = 0; i < SUN8I_VI_SCALER_COEFF_COUNT; i++)
> +               regmap_write(map, SUN8I_SCALER_VSU_YVCOEFF(base, i),
> +                            lan2coefftab32[offset + i]);
> +
> +       offset = sun8i_vi_scaler_coef_index(hstep / format->hsub) *
> +                       SUN8I_VI_SCALER_COEFF_COUNT;
> +       for (i = 0; i < SUN8I_VI_SCALER_COEFF_COUNT; i++) {
>                 regmap_write(map, SUN8I_SCALER_VSU_CHCOEFF0(base, i),
>                              ch_left[offset + i]);
>                 regmap_write(map, SUN8I_SCALER_VSU_CHCOEFF1(base, i),
>                              ch_right[offset + i]);
>         }
> -
> -       offset = sun8i_vi_scaler_coef_index(hstep) *
> +       offset = sun8i_vi_scaler_coef_index(vstep / format->vsub) *
>                         SUN8I_VI_SCALER_COEFF_COUNT;
> -       for (i = 0; i < SUN8I_VI_SCALER_COEFF_COUNT; i++) {
> -               regmap_write(map, SUN8I_SCALER_VSU_YVCOEFF(base, i),
> -                            lan2coefftab32[offset + i]);
> +       for (i = 0; i < SUN8I_VI_SCALER_COEFF_COUNT; i++)
>                 regmap_write(map, SUN8I_SCALER_VSU_CVCOEFF(base, i),
>                              cy[offset + i]);
> -       }
>  }
>
>  void sun8i_vi_scaler_enable(struct sun8i_layer *layer, bool enable)
> --
> 2.43.0
>