[PATCH v6 19/36] 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.

Reviewed-by: Dave Stevenson <dave.stevenson at raspberrypi.com>
Signed-off-by: Maxime Ripard <mripard at kernel.org>
---
 drivers/gpu/drm/drm_atomic.c                       |  1 +
 drivers/gpu/drm/drm_atomic_state_helper.c          | 44 ++++++++++++++++++++++
 .../gpu/drm/tests/drm_atomic_state_helper_test.c   |  3 ++
 include/drm/drm_connector.h                        |  5 +++
 4 files changed, 53 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 47fd2a7ca9e1..ec6c6beda5c9 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1151,6 +1151,7 @@ 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 34aee5232974..ac77d47a0ce3 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -683,6 +683,41 @@ static bool hdmi_is_full_range(const struct drm_connector *connector,
 	return drm_default_rgb_quant_range(mode) == HDMI_QUANTIZATION_RANGE_FULL ? true : false;
 }
 
+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)
+{
+	enum drm_mode_status status;
+	unsigned long long clock;
+
+	clock = drm_connector_hdmi_compute_mode_clock(mode, bpc, fmt);
+	if (!clock)
+		return -EINVAL;
+
+	status = hdmi_clock_valid(connector, mode, clock);
+	if (status != 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
@@ -702,9 +737,18 @@ 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_mode(new_state);
+	int ret;
 
 	new_state->hdmi.is_full_range = hdmi_is_full_range(connector, new_state);
 
+	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 ||
 	    old_state->hdmi.output_format != new_state->hdmi.output_format) {
diff --git a/drivers/gpu/drm/tests/drm_atomic_state_helper_test.c b/drivers/gpu/drm/tests/drm_atomic_state_helper_test.c
index 4e2ec436987b..d3f35600a9f9 100644
--- a/drivers/gpu/drm/tests/drm_atomic_state_helper_test.c
+++ b/drivers/gpu/drm/tests/drm_atomic_state_helper_test.c
@@ -70,6 +70,9 @@ static int light_up_connector(struct kunit *test,
 	conn_state = drm_atomic_get_connector_state(state, connector);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, conn_state);
 
+	conn_state->hdmi.output_bpc = connector->max_bpc;
+	conn_state->hdmi.output_format = HDMI_COLORSPACE_RGB;
+
 	ret = drm_atomic_set_crtc_for_connector(conn_state, crtc);
 	KUNIT_EXPECT_EQ(test, ret, 0);
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 0cc5a8732664..59016d9c17f5 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1085,6 +1085,11 @@ 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;
 };
 

-- 
2.43.0