drm/amd/display: Add freesync video modes based on preferred modes

[Why]
While possible for userspace to create and add custom mode based off the
optimized mode for the connected display which differs only in front porch
timing, this patch set adds a list of common video modes in advance.

The list of common video refresh rates is small, well known and the optimized
mode has specific requirements to be able to enable HW frame doubling and
tripling so it makes most sense to create the modes that video players will need
in advance. The optimized mode matches the preferred mode resolution but has the
highest refresh rate available to enable the largest front porch extension.

[How]
Find the optimized mode and store it on the connector so we can check it
later during our optimized modeset.

Prepopulate the mode list with a list of common video mades based on the
optimized mode (but with a longer front porch) if the panel doesn't support a
variant of the mode natively.

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -5172,6 +5172,59 @@ static void dm_enable_per_frame_crtc_master_sync(struct dc_state *context)
 	set_master_stream(context->streams, context->stream_count);
 }
 
+static struct drm_display_mode *
+get_highest_refresh_rate_mode(struct amdgpu_dm_connector *aconnector,
+			  bool use_probed_modes)
+{
+	struct drm_display_mode *m, *m_pref = NULL;
+	u16 current_refresh, highest_refresh;
+	struct list_head *list_head = use_probed_modes ?
+						    &aconnector->base.probed_modes :
+						    &aconnector->base.modes;
+
+	if (aconnector->freesync_vid_base.clock != 0)
+		return &aconnector->freesync_vid_base;
+
+	/* Find the preferred mode */
+	list_for_each_entry (m, list_head, head) {
+		if (m->type & DRM_MODE_TYPE_PREFERRED) {
+			m_pref = m;
+			break;
+		}
+	}
+
+	if (!m_pref) {
+		/* Probably an EDID with no preferred mode. Fallback to first entry */
+		m_pref = list_first_entry_or_null(
+			&aconnector->base.modes, struct drm_display_mode, head);
+		if (!m_pref) {
+			DRM_DEBUG_DRIVER("No preferred mode found in EDID\n");
+			return NULL;
+		}
+	}
+
+	highest_refresh = drm_mode_vrefresh(m_pref);
+
+	/*
+	 * Find the mode with highest refresh rate with same resolution.
+	 * For some monitors, preferred mode is not the mode with highest
+	 * supported refresh rate.
+	 */
+	list_for_each_entry (m, list_head, head) {
+		current_refresh  = drm_mode_vrefresh(m);
+
+		if (m->hdisplay == m_pref->hdisplay &&
+		    m->vdisplay == m_pref->vdisplay &&
+		    highest_refresh < current_refresh) {
+			highest_refresh = current_refresh;
+			m_pref = m;
+		}
+	}
+
+	aconnector->freesync_vid_base = *m_pref;
+	return m_pref;
+}
+
 static struct dc_stream_state *
 create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
 		       const struct drm_display_mode *drm_mode,
@@ -6973,6 +7026,107 @@ static void amdgpu_dm_connector_ddc_get_modes(struct drm_connector *connector,
 	}
 }
 
+static bool is_duplicate_mode(struct amdgpu_dm_connector *aconnector,
+			      struct drm_display_mode *mode)
+{
+	struct drm_display_mode *m;
+
+	list_for_each_entry (m, &aconnector->base.probed_modes, head) {
+		if (drm_mode_equal(m, mode))
+			return true;
+	}
+
+	return false;
+}
+
+static uint add_fs_modes(struct amdgpu_dm_connector *aconnector)
+{
+	const struct drm_display_mode *m;
+	struct drm_display_mode *new_mode;
+	uint i;
+	uint32_t new_modes_count = 0;
+
+	/* Standard FPS values
+	 *
+	 * 23.976   - TV/NTSC
+	 * 24 	    - Cinema
+	 * 25 	    - TV/PAL
+	 * 29.97    - TV/NTSC
+	 * 30 	    - TV/NTSC
+	 * 48 	    - Cinema HFR
+	 * 50 	    - TV/PAL
+	 * 60 	    - Commonly used
+	 * 48,72,96 - Multiples of 24
+	 */
+	const uint32_t common_rates[] = { 23976, 24000, 25000, 29970, 30000,
+					 48000, 50000, 60000, 72000, 96000 };
+
+	/*
+	 * Find mode with highest refresh rate with the same resolution
+	 * as the preferred mode. Some monitors report a preferred mode
+	 * with lower resolution than the highest refresh rate supported.
+	 */
+
+	m = get_highest_refresh_rate_mode(aconnector, true);
+	if (!m)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(common_rates); i++) {
+		uint64_t target_vtotal, target_vtotal_diff;
+		uint64_t num, den;
+
+		if (drm_mode_vrefresh(m) * 1000 < common_rates[i])
+			continue;
+
+		if (common_rates[i] < aconnector->min_vfreq * 1000 ||
+		    common_rates[i] > aconnector->max_vfreq * 1000)
+			continue;
+
+		num = (unsigned long long)m->clock * 1000 * 1000;
+		den = common_rates[i] * (unsigned long long)m->htotal;
+		target_vtotal = div_u64(num, den);
+		target_vtotal_diff = target_vtotal - m->vtotal;
+
+		/* Check for illegal modes */
+		if (m->vsync_start + target_vtotal_diff < m->vdisplay ||
+		    m->vsync_end + target_vtotal_diff < m->vsync_start ||
+		    m->vtotal + target_vtotal_diff < m->vsync_end)
+			continue;
+
+		new_mode = drm_mode_duplicate(aconnector->base.dev, m);
+		if (!new_mode)
+			goto out;
+
+		new_mode->vtotal += (u16)target_vtotal_diff;
+		new_mode->vsync_start += (u16)target_vtotal_diff;
+		new_mode->vsync_end += (u16)target_vtotal_diff;
+		new_mode->type &= ~DRM_MODE_TYPE_PREFERRED;
+		new_mode->type |= DRM_MODE_TYPE_DRIVER;
+
+		if (!is_duplicate_mode(aconnector, new_mode)) {
+			drm_mode_probed_add(&aconnector->base, new_mode);
+			new_modes_count += 1;
+		} else
+			drm_mode_destroy(aconnector->base.dev, new_mode);
+	}
+ out:
+	return new_modes_count;
+}
+
+static void amdgpu_dm_connector_add_freesync_modes(struct drm_connector *connector,
+						   struct edid *edid)
+{
+	struct amdgpu_dm_connector *amdgpu_dm_connector =
+		to_amdgpu_dm_connector(connector);
+
+	if (!(amdgpu_freesync_vid_mode && edid))
+		return;
+	
+	if (amdgpu_dm_connector->max_vfreq - amdgpu_dm_connector->min_vfreq > 10)
+		amdgpu_dm_connector->num_modes +=
+			add_fs_modes(amdgpu_dm_connector);
+}
+
 static int amdgpu_dm_connector_get_modes(struct drm_connector *connector)
 {
 	struct amdgpu_dm_connector *amdgpu_dm_connector =
@@ -6988,6 +7142,7 @@ static int amdgpu_dm_connector_get_modes(struct drm_connector *connector)
 	} else {
 		amdgpu_dm_connector_ddc_get_modes(connector, edid);
 		amdgpu_dm_connector_add_common_modes(encoder, connector);
+		amdgpu_dm_connector_add_freesync_modes(connector, edid);
 	}
 	amdgpu_dm_fbc_init(connector);
 

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -440,6 +440,8 @@ struct amdgpu_dm_connector {
 #endif
 	bool force_yuv420_output;
 	struct dsc_preferred_settings dsc_settings;
+	/* Cached display modes */
+	struct drm_display_mode freesync_vid_base;
 };
 
 #define to_amdgpu_dm_connector(x) container_of(x, struct amdgpu_dm_connector, base)