[PATCH] gpu: color: eliminate implicit conversion about enum type

[Alex Deucher]

On Mon, Sep 19, 2022 at 3:19 AM Zeng Heng <zengheng4 at huawei.com> wrote:
>
> Fix below compile warning when open enum-conversion
> option check:
>
> drivers/gpu/drm/amd/amdgpu/../display/modules/color/color_gamma.c:
> In function ‘apply_degamma_for_user_regamma’:
> drivers/gpu/drm/amd/amdgpu/../display/modules/color/color_gamma.c:1695:29:
> error: implicit conversion from ‘enum <anonymous>’ to ‘enum dc_transfer_func_predefined’ [-Werror=enum-conversion]
>  1695 |  build_coefficients(&coeff, true);
>       |                             ^~~~
>
> As 'build_coefficients' definition, it needs enum
> 'dc_transfer_func_predefined' type acts as the
> second argument, instead of bool-type one.
>
> The numerical values of TRANSFER_FUNCTION_BT709 & true
> happen to be the same, so there is no change in
> behavior.

This looks like a regression from:

commit 9b3d76527f6ea50270f7f7ac749493b41783e8bd
Author: Jaehyun Chung <jaehyun.chung at amd.com>
Date:   Mon Aug 30 16:46:42 2021 -0400

    drm/amd/display: Revert adding degamma coefficients

    [Why]
    Degamma coefficients are calculated in our degamma formula using
    the regamma coefficients. We do not need to add separate degamma
    coefficients.

    [How]
    Remove the change to add separate degamma coefficients.

    Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac at amd.com>
    Acked-by: Mikita Lipski <mikita.lipski at amd.com>
    Signed-off-by: Jaehyun Chung <jaehyun.chung at amd.com>
    Tested-by: Daniel Wheeler <daniel.wheeler at amd.com>
    Signed-off-by: Alex Deucher <alexander.deucher at amd.com>

Which seems to improperly revert:
commit d020970959169627d59a711769f8c4b87bf5f90c
Author: Jaehyun Chung <jaehyun.chung at amd.com>
Date:   Tue Aug 24 14:05:48 2021 -0400

    drm/amd/display: Add regamma/degamma coefficients and set sRGB
when TF is BT709

    [Why]
    In YUV case, need to set the input TF to sRGB instead of BT709,
    even though the input TF type is distributed. SRGB was not
    being used because pixel format was not being set in the
    surface update sequence.
    Also, we were using the same coefficients for degamma and
    regamma formula, causing the cutoff point of the linear
    section of the curve to be incorrect.

    [How]
    Set pixel format in the surface update sequence. Add separate
    coefficient arrays for regamma and degamma.

    Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac at amd.com>
    Acked-by: Mikita Lipski <mikita.lipski at amd.com>
    Signed-off-by: Jaehyun Chung <jaehyun.chung at amd.com>
    Tested-by: Daniel Wheeler <daniel.wheeler at amd.com>
    Signed-off-by: Alex Deucher <alexander.deucher at amd.com>

I think the proper fix is to set it to:
build_coefficients(&coeff, TRANSFER_FUNCTION_SRGB);

Alex

>
> Signed-off-by: Zeng Heng <zengheng4 at huawei.com>
> ---
>  drivers/gpu/drm/amd/display/modules/color/color_gamma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/display/modules/color/color_gamma.c b/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
> index 04f7656906ca..2f807d787c77 100644
> --- a/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
> +++ b/drivers/gpu/drm/amd/display/modules/color/color_gamma.c
> @@ -1692,7 +1692,7 @@ static void apply_degamma_for_user_regamma(struct pwl_float_data_ex *rgb_regamma
>         struct pwl_float_data_ex *rgb = rgb_regamma;
>         const struct hw_x_point *coord_x = coordinates_x;
>
> -       build_coefficients(&coeff, true);
> +       build_coefficients(&coeff, TRANSFER_FUNCTION_BT709);
>
>         i = 0;
>         while (i != hw_points_num + 1) {
> --
> 2.25.1
>