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Subject: Re: [PATCH 2/3] drm/komeda: Add drm_ctm_to_coeffs()
Thread-Topic: [PATCH 2/3] drm/komeda: Add drm_ctm_to_coeffs()
Thread-Index: AQHVd0syoKU25huCdkWmRqYuLiJjnqdEDx0A
Date:   Mon, 30 Sep 2019 11:04:39 +0000
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Hi James,

On Mon, Sep 30, 2019 at 04:54:41AM +0000, james qian wang (Arm Technology C=
hina) wrote:
> This function is used to convert drm_color_ctm S31.32 sign-magnitude
> value to komeda required Q2.12 2's complement
>=20
> Signed-off-by: james qian wang (Arm Technology China) <james.qian.wang@ar=
m.com>
> ---
>  .../arm/display/komeda/komeda_color_mgmt.c    | 27 +++++++++++++++++++
>  .../arm/display/komeda/komeda_color_mgmt.h    |  1 +
>  2 files changed, 28 insertions(+)
>=20
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c b/dri=
vers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c
> index c180ce70c26c..c92c82eebddb 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.c
> @@ -117,3 +117,30 @@ void drm_lut_to_fgamma_coeffs(struct drm_property_bl=
ob *lut_blob, u32 *coeffs)
>  {
>  	drm_lut_to_coeffs(lut_blob, coeffs, sector_tbl, ARRAY_SIZE(sector_tbl))=
;
>  }
> +
> +/* Convert from S31.32 sign-magnitude to HW Q2.12 2's complement */
> +static s32 drm_ctm_s31_32_to_q2_12(u64 input)
> +{
> +	u64 mag =3D (input & ~BIT_ULL(63)) >> 20;
> +	bool negative =3D !!(input & BIT_ULL(63));
> +	u32 val;
> +
> +	/* the range of signed 2s complement is [-2^n, 2^n - 1] */
> +	val =3D clamp_val(mag, 0, negative ? BIT(14) : BIT(14) - 1);
> +
> +	return negative ? 0 - val : val;
> +}

This function looks generally useful. Should it be in DRM core
(assuming there isn't already one there)?

You can use a parameter to determine the number of bits desired in the
output.

Thanks,
-Brian

> +
> +void drm_ctm_to_coeffs(struct drm_property_blob *ctm_blob, u32 *coeffs)
> +{
> +	struct drm_color_ctm *ctm;
> +	u32 i;
> +
> +	if (!ctm_blob)
> +		return;
> +
> +	ctm =3D ctm_blob->data;
> +
> +	for (i =3D 0; i < KOMEDA_N_CTM_COEFFS; i++)
> +		coeffs[i] =3D drm_ctm_s31_32_to_q2_12(ctm->matrix[i]);
> +}
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h b/dri=
vers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h
> index 08ab69281648..2f4668466112 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_color_mgmt.h
> @@ -18,6 +18,7 @@
>  #define KOMEDA_N_CTM_COEFFS		9
> =20
>  void drm_lut_to_fgamma_coeffs(struct drm_property_blob *lut_blob, u32 *c=
oeffs);
> +void drm_ctm_to_coeffs(struct drm_property_blob *ctm_blob, u32 *coeffs);
> =20
>  const s32 *komeda_select_yuv2rgb_coeffs(u32 color_encoding, u32 color_ra=
nge);
> =20
> --=20
> 2.20.1
>=20