linux-kernel - [PATCH RFC v3 08/37] drm/connector: hdmi: Calculate TMDS character rate

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Message-Id: <20231031-kms-hdmi-connector-state-v3-8-328b0fae43a7@kernel.org>
Date:   Tue, 31 Oct 2023 17:48:21 +0100
From:   Maxime Ripard <mripard@...nel.org>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>,
        Jonathan Corbet <corbet@....net>,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>
Cc:     Hans Verkuil <hverkuil@...all.nl>, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        Maxime Ripard <mripard@...nel.org>
Subject: [PATCH RFC v3 08/37] drm/connector: hdmi: Calculate TMDS character
 rate

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@...nel.org>
---
 drivers/gpu/drm/drm_atomic.c              |  1 +
 drivers/gpu/drm/drm_atomic_state_helper.c | 44 +++++++++++++++++++++++++++++++
 include/drm/drm_connector.h               |  5 ++++
 3 files changed, 50 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 0ebe1142dcfe..fed9d437a4a6 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1150,6 +1150,7 @@ 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 37262dd002c8..480fa3445f40 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -670,6 +670,41 @@ static bool hdmi_is_full_range(const struct drm_connector *connector,
 	return drm_default_rgb_quant_range(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)
+{
+	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
@@ -689,9 +724,18 @@ 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/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 781a5726a26a..93613c57c6de 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1072,6 +1072,11 @@ 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