drm: New function to get luminance range based on static hdr metadata

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.

Add new data structure (drm_luminance_range_inf) to store luminance range
calculated using data from EDID's static hdr metadata block. Add this new
struct as a part of drm_display_info struct.

v3: Squashed adding drm_luminance_range_info patch here
v2: Calculate range during edid parsing

Cc: Roman Li <roman.li@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220719095700.14923-2-jouni.hogander@intel.com

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index bbc25e3b7220a2ffe68b8288d2af56279b1ae208..90a5e26eafa837ca05c0d084fc845b1d077a0d3e 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -5165,6 +5165,51 @@ 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
+       };
+       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
+        * 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;
+}
+
 static uint8_t eotf_supported(const u8 *edid_ext)
 {
        return edid_ext[2] &
@@ -5196,8 +5241,12 @@ 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
@@ -6101,6 +6150,7 @@ static void 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;

diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 2c6fa746efac23452879ce41081fdecd28f04803..248206bbd975ed8dc0fd217f868b88131e5659b0 100644 (file)
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -323,6 +323,22 @@ struct drm_monitor_range_info {
        u8 max_vfreq;
 };
 
+/**
+ * struct drm_luminance_range_info - Panel's luminance range for
+ * &drm_display_info. Calculated using data in EDID
+ *
+ * This struct is used to store a luminance range supported by panel
+ * as calculated using data from EDID's static hdr metadata.
+ *
+ * @min_luminance: This is the min supported luminance value
+ *
+ * @max_luminance: This is the max supported luminance value
+ */
+struct drm_luminance_range_info {
+       u32 min_luminance;
+       u32 max_luminance;
+};
+
 /**
  * enum drm_privacy_screen_status - privacy screen status
  *
@@ -624,6 +640,11 @@ struct drm_display_info {
         */
        struct drm_monitor_range_info monitor_range;
 
+       /**
+        * @luminance_range: Luminance range supported by panel
+        */
+       struct drm_luminance_range_info luminance_range;
+
        /**
         * @mso_stream_count: eDP Multi-SST Operation (MSO) stream count from
         * the DisplayID VESA vendor block. 0 for conventional Single-Stream