On Mon, 20 Jun 2022, Jouni Högander <jouni.hogander@xxxxxxxxx> wrote:
> Split luminance min/max calculation using static hdr metadata from
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c:update_connector_ext_caps
> into drm/drm_edid.c and use it during edid parsing. Calculated range is
> stored into connector->display_info->luminance_range.
>
> v2: Calculate range during edid parsing
>
> Cc: Roman Li <roman.li@xxxxxxx>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx>
> Cc: Harry Wentland <harry.wentland@xxxxxxx>
> Cc: Lyude Paul <lyude@xxxxxxxxxx>
> Cc: Mika Kahola <mika.kahola@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> Signed-off-by: Jouni Högander <jouni.hogander@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_edid.c | 50 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 2bdaf1e34a9d..3b367100290f 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -5014,6 +5014,49 @@ static void fixup_detailed_cea_mode_clock(struct drm_display_mode *mode)
> mode->clock = clock;
> }
>
> +static void drm_calculate_luminance_range(struct drm_connector *connector)
> +{
> + struct hdr_static_metadata *hdr_metadata = &connector->hdr_sink_metadata.hdmi_type1;
> + struct drm_luminance_range_info *luminance_range =
> + &connector->display_info.luminance_range;
> + static const u8 pre_computed_values[] = {
> + 50, 51, 52, 53, 55, 56, 57, 58, 59, 61, 62, 63, 65, 66, 68, 69,
> + 71, 72, 74, 75, 77, 79, 81, 82, 84, 86, 88, 90, 92, 94, 96, 98};
Nitpick, newline before };
> + u32 max_avg, min_cll, max, min, q, r;
> +
> + if (!(hdr_metadata->metadata_type & BIT(HDMI_STATIC_METADATA_TYPE1)))
> + return;
> +
> + max_avg = hdr_metadata->max_fall;
> + min_cll = hdr_metadata->min_cll;
> +
> + /* From the specification (CTA-861-G), for calculating the maximum
Nitpick, newline after /*.
> + * luminance we need to use:
> + * Luminance = 50*2**(CV/32)
> + * Where CV is a one-byte value.
> + * For calculating this expression we may need float point precision;
> + * to avoid this complexity level, we take advantage that CV is divided
> + * by a constant. From the Euclids division algorithm, we know that CV
> + * can be written as: CV = 32*q + r. Next, we replace CV in the
> + * Luminance expression and get 50*(2**q)*(2**(r/32)), hence we just
> + * need to pre-compute the value of r/32. For pre-computing the values
> + * We just used the following Ruby line:
> + * (0...32).each {|cv| puts (50*2**(cv/32.0)).round}
> + * The results of the above expressions can be verified at
> + * pre_computed_values.
> + */
> + q = max_avg >> 5;
> + r = max_avg % 32;
> + max = (1 << q) * pre_computed_values[r];
> +
> + /* min luminance: maxLum * (CV/255)^2 / 100 */
> + q = DIV_ROUND_CLOSEST(min_cll, 255);
> + min = max * DIV_ROUND_CLOSEST((q * q), 100);
> +
> + luminance_range->min_luminance = min;
> + luminance_range->max_luminance = max;
I'll just trust this; not going to start verifying.
Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> +}
> +
> static uint8_t eotf_supported(const u8 *edid_ext)
> {
> return edid_ext[2] &
> @@ -5045,8 +5088,12 @@ drm_parse_hdr_metadata_block(struct drm_connector *connector, const u8 *db)
> connector->hdr_sink_metadata.hdmi_type1.max_cll = db[4];
> if (len >= 5)
> connector->hdr_sink_metadata.hdmi_type1.max_fall = db[5];
> - if (len >= 6)
> + if (len >= 6) {
> connector->hdr_sink_metadata.hdmi_type1.min_cll = db[6];
> +
> + /* Calculate only when all values are available */
> + drm_calculate_luminance_range(connector);
> + }
> }
>
> static void
> @@ -5951,6 +5998,7 @@ drm_reset_display_info(struct drm_connector *connector)
>
> info->non_desktop = 0;
> memset(&info->monitor_range, 0, sizeof(info->monitor_range));
> + memset(&info->luminance_range, 0, sizeof(info->luminance_range));
>
> info->mso_stream_count = 0;
> info->mso_pixel_overlap = 0;
--
Jani Nikula, Intel Open Source Graphics Center
