[PATCH RFC 07/13] 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@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_hdmi_connector.c | 77 ++++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h          | 11 ++++++
 2 files changed, 88 insertions(+)

diff --git a/drivers/gpu/drm/drm_hdmi_connector.c b/drivers/gpu/drm/drm_hdmi_connector.c
index 55f685c0095b..e49782a284a5 100644
--- a/drivers/gpu/drm/drm_hdmi_connector.c
+++ b/drivers/gpu/drm/drm_hdmi_connector.c
@@ -82,6 +82,7 @@ __drm_atomic_helper_hdmi_connector_duplicate_state(struct drm_hdmi_connector *hd
 	struct drm_hdmi_connector_state *old_hdmi_state =
 		connector_state_to_hdmi_connector_state(old_state);
 
+	new_hdmi_state->tmds_char_rate = old_hdmi_state->tmds_char_rate;
 	new_hdmi_state->output_bpc = old_hdmi_state->output_bpc;
 	new_hdmi_state->output_format = old_hdmi_state->output_format;
 	new_hdmi_state->broadcast_rgb = old_hdmi_state->broadcast_rgb;
@@ -257,6 +258,69 @@ connector_state_get_adjusted_mode(const struct drm_connector_state *state)
 	return &crtc_state->adjusted_mode;
 }
 
+static enum drm_mode_status
+drm_hdmi_connector_clock_valid(const struct drm_hdmi_connector *hdmi_connector,
+			       const struct drm_display_mode *mode,
+			       unsigned long long clock)
+{
+	const struct drm_connector *connector = &hdmi_connector->base;
+	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;
+}
+
+/**
+ * drm_hdmi_connector_compute_mode_clock() - Computes the TMDS Character Rate
+ * @mode: Display mode to compute the clock for
+ * @bpc: Bits per character
+ * @fmt: Output Pixel Format used
+ *
+ * Returns the TMDS Character Rate for a given mode, bpc count and output format.
+ *
+ * RETURNS:
+ * The TMDS Character Rate, in Hertz
+ */
+unsigned long long
+drm_hdmi_connector_compute_mode_clock(const struct drm_display_mode *mode,
+				      unsigned int bpc,
+				      enum hdmi_colorspace fmt)
+{
+	unsigned long long clock = mode->clock * 1000ULL;
+
+	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
+		clock = clock * 2;
+
+	if (fmt == HDMI_COLORSPACE_YUV422)
+		bpc = 8;
+
+	clock = clock * bpc;
+	do_div(clock, 8);
+
+	return clock;
+}
+EXPORT_SYMBOL(drm_hdmi_connector_compute_mode_clock);
+
+static int
+drm_hdmi_connector_compute_clock(const struct drm_hdmi_connector *hdmi_connector,
+				 struct drm_hdmi_connector_state *hdmi_state,
+				 const struct drm_display_mode *mode,
+				 unsigned int bpc,
+				 enum hdmi_colorspace fmt)
+{
+	unsigned long long clock;
+
+	clock = drm_hdmi_connector_compute_mode_clock(mode, bpc, fmt);
+	if (!drm_hdmi_connector_clock_valid(hdmi_connector, mode, clock) != MODE_OK)
+		return -EINVAL;
+
+	hdmi_state->tmds_char_rate = clock;
+
+	return 0;
+}
+
 /**
  * drm_atomic_helper_hdmi_connector_atomic_check() - Helper to check HDMI connector atomic state
  * @connector: the parent connector this state refers to
@@ -275,6 +339,8 @@ connector_state_get_adjusted_mode(const struct drm_connector_state *state)
 int drm_atomic_helper_hdmi_connector_atomic_check(struct drm_connector *connector,
 						  struct drm_atomic_state *state)
 {
+	struct drm_hdmi_connector *hdmi_connector =
+		connector_to_hdmi_connector(connector);
 	struct drm_connector_state *old_state =
 		drm_atomic_get_old_connector_state(state, connector);
 	struct drm_hdmi_connector_state *old_hdmi_state =
@@ -283,6 +349,16 @@ int drm_atomic_helper_hdmi_connector_atomic_check(struct drm_connector *connecto
 		drm_atomic_get_new_connector_state(state, connector);
 	struct drm_hdmi_connector_state *new_hdmi_state =
 		connector_state_to_hdmi_connector_state(new_state);
+	const struct drm_display_mode *mode =
+		connector_state_get_adjusted_mode(new_state);
+	int ret;
+
+	ret = drm_hdmi_connector_compute_clock(hdmi_connector, new_hdmi_state,
+					       mode,
+					       new_hdmi_state->output_bpc,
+					       new_hdmi_state->output_format);
+	if (!ret)
+		return ret;
 
 	if (old_hdmi_state->broadcast_rgb != new_hdmi_state->broadcast_rgb ||
 	    old_hdmi_state->output_format != new_hdmi_state->output_format ||
@@ -374,6 +450,7 @@ void drm_atomic_helper_hdmi_connector_print_state(struct drm_printer *p,
 	drm_printf(p, "\toutput_bpc=%u\n", hdmi_state->output_bpc);
 	drm_printf(p, "\toutput_format=%s\n",
 		   drm_hdmi_connector_get_output_format_name(hdmi_state->output_format));
+	drm_printf(p, "\ttmds_char_rate=%llu\n", hdmi_state->tmds_char_rate);
 }
 EXPORT_SYMBOL(drm_atomic_helper_hdmi_connector_print_state);
 
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 995700110a16..03c5af34323d 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -38,6 +38,7 @@ struct drm_connector_helper_funcs;
 struct drm_modeset_acquire_ctx;
 struct drm_device;
 struct drm_crtc;
+struct drm_display_mode;
 struct drm_encoder;
 struct drm_panel;
 struct drm_property;
@@ -2085,6 +2086,11 @@ struct drm_hdmi_connector_state {
 	 */
 	enum hdmi_colorspace output_format;
 
+	/**
+	 * @tmds_char_rate: TMDS Character Rate, in Hz.
+	 */
+	unsigned long long tmds_char_rate;
+
 	/**
 	 * @broadcast_rgb: Connector property to pass the Broadcast RGB
 	 * selection value.
@@ -2146,6 +2152,11 @@ struct drm_hdmi_connector {
 #define connector_to_hdmi_connector(connector) \
 	container_of_const(connector, struct drm_hdmi_connector, base)
 
+unsigned long long
+drm_hdmi_connector_compute_mode_clock(const struct drm_display_mode *mode,
+				      unsigned int bpc,
+				      enum hdmi_colorspace fmt);
+
 int drmm_hdmi_connector_init(struct drm_device *dev,
 			     struct drm_hdmi_connector *hdmi_connector,
 			     const struct drm_connector_funcs *funcs,

-- 
2.41.0