[PATCH RFC v2 08/37] drm/connector: hdmi: Calculate TMDS character rate

[Maxime Ripard]

Most HDMI drivers have some code to calculate the TMDS character rate,
usually to adjust an internal clock to match what the mode requires.

Since the TMDS character rates mostly depends on the resolution, whether
we need to repeat pixels or not, the bpc count and the format, we can
now derive it from the HDMI connector state that stores all those infos
and remove the duplication from drivers.

Signed-off-by: Maxime Ripard <mripard at kernel.org>
---
 drivers/gpu/drm/drm_atomic.c              |  1 +
 drivers/gpu/drm/drm_atomic_state_helper.c | 39 +++++++++++++++++++++++++++++++
 include/drm/drm_connector.h               |  5 ++++
 3 files changed, 45 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index a50589b88a79..4cdbd8979d8d 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1149,6 +1149,7 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
 		drm_printf(p, "\toutput_bpc=%u\n", state->hdmi.output_bpc);
 		drm_printf(p, "\toutput_format=%s\n",
 			   drm_hdmi_connector_get_output_format_name(state->hdmi.output_format));
+		drm_printf(p, "\ttmds_char_rate=%llu\n", state->hdmi.tmds_char_rate);
 	}
 
 	if (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
index 3e0c10f2c456..0417d964a590 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -635,6 +635,36 @@ connector_state_get_adjusted_mode(const struct drm_connector_state *state)
 	return &crtc_state->adjusted_mode;
 }
 
+static enum drm_mode_status
+hdmi_clock_valid(const struct drm_connector *connector,
+		 const struct drm_display_mode *mode,
+		 unsigned long long clock)
+{
+	const struct drm_display_info *info = &connector->display_info;
+
+	if (info->max_tmds_clock && clock > info->max_tmds_clock * 1000)
+		return MODE_CLOCK_HIGH;
+
+	return MODE_OK;
+}
+
+static int
+hdmi_compute_clock(const struct drm_connector *connector,
+		   struct drm_connector_state *state,
+		   const struct drm_display_mode *mode,
+		   unsigned int bpc, enum hdmi_colorspace fmt)
+{
+	unsigned long long clock;
+
+	clock = drm_connector_hdmi_compute_mode_clock(mode, bpc, fmt);
+	if (!hdmi_clock_valid(connector, mode, clock) != MODE_OK)
+		return -EINVAL;
+
+	state->hdmi.tmds_char_rate = clock;
+
+	return 0;
+}
+
 /**
  * drm_atomic_helper_connector_hdmi_check() - Helper to check HDMI connector atomic state
  * @connector: DRM Connector
@@ -654,6 +684,15 @@ int drm_atomic_helper_connector_hdmi_check(struct drm_connector *connector,
 		drm_atomic_get_old_connector_state(state, connector);
 	struct drm_connector_state *new_state =
 		drm_atomic_get_new_connector_state(state, connector);
+	const struct drm_display_mode *mode =
+		connector_state_get_adjusted_mode(new_state);
+	int ret;
+
+	ret = hdmi_compute_clock(connector, new_state, mode,
+				 new_state->hdmi.output_bpc,
+				 new_state->hdmi.output_format);
+	if (!ret)
+		return ret;
 
 	if (old_state->hdmi.broadcast_rgb != new_state->hdmi.broadcast_rgb ||
 	    old_state->hdmi.output_bpc != new_state->hdmi.output_bpc ||
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index d74e9c64ee88..025380ebd128 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1069,6 +1069,11 @@ struct drm_connector_state {
 		 * @output_format: Pixel format to output in.
 		 */
 		enum hdmi_colorspace output_format;
+
+		/**
+		 * @tmds_char_rate: TMDS Character Rate, in Hz.
+		 */
+		unsigned long long tmds_char_rate;
 	} hdmi;
 };
 

-- 
2.41.0