drm: support routines for HDMI/DP ELD

ELD (EDID-Like Data) describes to the HDMI/DP audio driver the audio
capabilities of the plugged monitor.

This adds drm_edid_to_eld() for converting EDID to ELD. The converted
ELD will be saved in a new drm_connector.eld[128] data field. This is
necessary because the graphics driver will need to fixup some of the
data fields (eg. HDMI/DP connection type, AV sync delay) before writing
to the hardware ELD buffer. drm_av_sync_delay() will help the graphics
drivers dynamically compute the AV sync delay for fixing-up the ELD.

ELD selection policy: it's possible for one encoder to be associated
with multiple connectors (ie. monitors), in which case the first found
ELD will be returned by drm_select_eld(). This policy may not be
suitable for all users, but let's start it simple first.

The impact of ELD selection policy: assume there are two monitors, one
supports stereo playback and the other has 8-channel output; cloned
display mode is used, so that the two monitors are associated with the
same internal encoder. If only the stereo playback capability is reported,
the user won't be able to start 8-channel playback; if the 8-channel ELD
is reported, then user space applications may send 8-channel samples
down, however the user may actually be listening to the 2-channel
monitor and not connecting speakers to the 8-channel monitor.

According to James, many TVs will either refuse the display anything or
pop-up an OSD warning whenever they receive hdmi audio which they cannot
handle. Eventually we will require configurability and/or per-monitor
audio control even when the video is cloned.

CC: Zhao Yakui <yakui.zhao@intel.com>
CC: Wang Zhenyu <zhenyu.z.wang@intel.com>
CC: Jeremy Bush <contractfrombelow@gmail.com>
CC: Christopher White <c.white@pulseforce.com>
CC: Pierre-Louis Bossart <pierre-louis.bossart@intel.com>
CC: Paul Menzel <paulepanter@users.sourceforge.net>
CC: James Cloos <cloos@jhcloos.com>
CC: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

3 files changed, 189 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 7425e5c9bd75..fe39c3570538 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1319,6 +1319,7 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
 #define HDMI_IDENTIFIER 0x000C03
 #define AUDIO_BLOCK     0x01
 #define VENDOR_BLOCK    0x03
+#define SPEAKER_BLOCK   0x04
 #define EDID_BASIC_AUDIO        (1 << 6)
 
 /**
@@ -1347,6 +1348,176 @@ u8 *drm_find_cea_extension(struct edid *edid)
 }
 EXPORT_SYMBOL(drm_find_cea_extension);
 
+static void
+parse_hdmi_vsdb(struct drm_connector *connector, uint8_t *db)
+{
+        connector->eld[5] |= (db[6] >> 7) << 1;  /* Supports_AI */
+
+        connector->dvi_dual = db[6] & 1;
+        connector->max_tmds_clock = db[7] * 5;
+
+        connector->latency_present[0] = db[8] >> 7;
+        connector->latency_present[1] = (db[8] >> 6) & 1;
+        connector->video_latency[0] = db[9];
+        connector->audio_latency[0] = db[10];
+        connector->video_latency[1] = db[11];
+        connector->audio_latency[1] = db[12];
+
+        DRM_LOG_KMS("HDMI: DVI dual %d, "
+                    "max TMDS clock %d, "
+                    "latency present %d %d, "
+                    "video latency %d %d, "
+                    "audio latency %d %d\n",
+                    connector->dvi_dual,
+                    connector->max_tmds_clock,
+              (int) connector->latency_present[0],
+              (int) connector->latency_present[1],
+                    connector->video_latency[0],
+                    connector->video_latency[1],
+                    connector->audio_latency[0],
+                    connector->audio_latency[1]);
+}
+
+static void
+monitor_name(struct detailed_timing *t, void *data)
+{
+        if (t->data.other_data.type == EDID_DETAIL_MONITOR_NAME)
+                *(u8 **)data = t->data.other_data.data.str.str;
+}
+
+/**
+ * drm_edid_to_eld - build ELD from EDID
+ * @connector: connector corresponding to the HDMI/DP sink
+ * @edid: EDID to parse
+ *
+ * Fill the ELD (EDID-Like Data) buffer for passing to the audio driver.
+ * Some ELD fields are left to the graphics driver caller:
+ * - Conn_Type
+ * - HDCP
+ * - Port_ID
+ */
+void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
+{
+        uint8_t *eld = connector->eld;
+        u8 *cea;
+        u8 *name;
+        u8 *db;
+        int sad_count = 0;
+        int mnl;
+        int dbl;
+
+        memset(eld, 0, sizeof(connector->eld));
+
+        cea = drm_find_cea_extension(edid);
+        if (!cea) {
+                DRM_DEBUG_KMS("ELD: no CEA Extension found\n");
+                return;
+        }
+
+        name = NULL;
+        drm_for_each_detailed_block((u8 *)edid, monitor_name, &name);
+        for (mnl = 0; name && mnl < 13; mnl++) {
+                if (name[mnl] == 0x0a)
+                        break;
+                eld[20 + mnl] = name[mnl];
+        }
+        eld[4] = (cea[1] << 5) | mnl;
+        DRM_DEBUG_KMS("ELD monitor %s\n", eld + 20);
+
+        eld[0] = 2 << 3;                /* ELD version: 2 */
+
+        eld[16] = edid->mfg_id[0];
+        eld[17] = edid->mfg_id[1];
+        eld[18] = edid->prod_code[0];
+        eld[19] = edid->prod_code[1];
+
+        for (db = cea + 4; db < cea + cea[2]; db += dbl + 1) {
+                dbl = db[0] & 0x1f;
+
+                switch ((db[0] & 0xe0) >> 5) {
+                case AUDIO_BLOCK:       /* Audio Data Block, contains SADs */
+                        sad_count = dbl / 3;
+                        memcpy(eld + 20 + mnl, &db[1], dbl);
+                        break;
+                case SPEAKER_BLOCK:     /* Speaker Allocation Data Block */
+                        eld[7] = db[1];
+                        break;
+                case VENDOR_BLOCK:
+                        /* HDMI Vendor-Specific Data Block */
+                        if (db[1] == 0x03 && db[2] == 0x0c && db[3] == 0)
+                                parse_hdmi_vsdb(connector, db);
+                        break;
+                default:
+                        break;
+                }
+        }
+        eld[5] |= sad_count << 4;
+        eld[2] = (20 + mnl + sad_count * 3 + 3) / 4;
+
+        DRM_DEBUG_KMS("ELD size %d, SAD count %d\n", (int)eld[2], sad_count);
+}
+EXPORT_SYMBOL(drm_edid_to_eld);
+
+/**
+ * drm_av_sync_delay - HDMI/DP sink audio-video sync delay in millisecond
+ * @connector: connector associated with the HDMI/DP sink
+ * @mode: the display mode
+ */
+int drm_av_sync_delay(struct drm_connector *connector,
+                      struct drm_display_mode *mode)
+{
+        int i = !!(mode->flags & DRM_MODE_FLAG_INTERLACE);
+        int a, v;
+
+        if (!connector->latency_present[0])
+                return 0;
+        if (!connector->latency_present[1])
+                i = 0;
+
+        a = connector->audio_latency[i];
+        v = connector->video_latency[i];
+
+        /*
+         * HDMI/DP sink doesn't support audio or video?
+         */
+        if (a == 255 || v == 255)
+                return 0;
+
+        /*
+         * Convert raw EDID values to millisecond.
+         * Treat unknown latency as 0ms.
+         */
+        if (a)
+                a = min(2 * (a - 1), 500);
+        if (v)
+                v = min(2 * (v - 1), 500);
+
+        return max(v - a, 0);
+}
+EXPORT_SYMBOL(drm_av_sync_delay);
+
+/**
+ * drm_select_eld - select one ELD from multiple HDMI/DP sinks
+ * @encoder: the encoder just changed display mode
+ * @mode: the adjusted display mode
+ *
+ * It's possible for one encoder to be associated with multiple HDMI/DP sinks.
+ * The policy is now hard coded to simply use the first HDMI/DP sink's ELD.
+ */
+struct drm_connector *drm_select_eld(struct drm_encoder *encoder,
+                                     struct drm_display_mode *mode)
+{
+        struct drm_connector *connector;
+        struct drm_device *dev = encoder->dev;
+
+        list_for_each_entry(connector, &dev->mode_config.connector_list, head)
+                if (connector->encoder == encoder && connector->eld[0])
+                        return connector;
+
+        return NULL;
+}
+EXPORT_SYMBOL(drm_select_eld);
+
 /**
  * drm_detect_hdmi_monitor - detect whether monitor is hdmi.
  * @edid: monitor EDID information
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 44335e57eaaa..802079809282 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -466,6 +466,8 @@ enum drm_connector_force {
 /* DACs should rarely do this without a lot of testing */
 #define DRM_CONNECTOR_POLL_DISCONNECT (1 << 2)
 
+#define MAX_ELD_BYTES   128
+
 /**
  * drm_connector - central DRM connector control structure
  * @crtc: CRTC this connector is currently connected to, NULL if none
@@ -523,6 +525,13 @@ struct drm_connector {
         uint32_t force_encoder_id;
         struct drm_encoder *encoder; /* currently active encoder */
 
+        /* EDID bits */
+        uint8_t eld[MAX_ELD_BYTES];
+        bool dvi_dual;
+        int max_tmds_clock;     /* in MHz */
+        bool latency_present[2];
+        int video_latency[2];   /* [0]: progressive, [1]: interlaced */
+        int audio_latency[2];
         int null_edid_counter; /* needed to workaround some HW bugs where we get all 0s */
 };
 
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index eacb415b309a..74ce91684629 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -230,4 +230,13 @@ struct edid {
 
 #define EDID_PRODUCT_ID(e) ((e)->prod_code[0] | ((e)->prod_code[1] << 8))
 
+struct drm_encoder;
+struct drm_connector;
+struct drm_display_mode;
+void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid);
+int drm_av_sync_delay(struct drm_connector *connector,
+                      struct drm_display_mode *mode);
+struct drm_connector *drm_select_eld(struct drm_encoder *encoder,
+                                     struct drm_display_mode *mode);
+
 #endif /* __DRM_EDID_H__ */