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From:   Maxime Ripard <mripard@kernel.org>
Date:   Wed, 20 Sep 2023 16:35:22 +0200
Subject: [PATCH RFC v2 07/37] drm/connector: hdmi: Add HDMI compute clock
 helper
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Message-Id: <20230920-kms-hdmi-connector-state-v2-7-17932daddd7d@kernel.org>
References: <20230920-kms-hdmi-connector-state-v2-0-17932daddd7d@kernel.org>
In-Reply-To: <20230920-kms-hdmi-connector-state-v2-0-17932daddd7d@kernel.org>
To:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>, Emma Anholt <emma@anholt.net>,
        Jonathan Corbet <corbet@lwn.net>,
        Sandy Huang <hjc@rock-chips.com>,
        =?utf-8?q?Heiko_St=C3=BCbner?= <heiko@sntech.de>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>
Cc:     Hans Verkuil <hverkuil@xs4all.nl>, dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        linux-rockchip@lists.infradead.org, linux-sunxi@lists.linux.dev,
        Maxime Ripard <mripard@kernel.org>
Precedence: bulk

A lot of HDMI drivers have some variation of the formula to calculate
the TMDS character rate from a mode, but few of them actually take all
parameters into account.

Let's create a helper to provide that rate taking all parameters into
account.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 drivers/gpu/drm/drm_connector.c | 31 +++++++++++++++++++++++++++++++
 include/drm/drm_connector.h     |  5 +++++
 2 files changed, 36 insertions(+)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index b01cb4783ea6..4c1af97971bb 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -2944,6 +2944,37 @@ void drm_connector_update_privacy_screen(const struct drm_connector_state *conne
 }
 EXPORT_SYMBOL(drm_connector_update_privacy_screen);
 
+/**
+ * drm_connector_hdmi_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_connector_hdmi_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_connector_hdmi_compute_mode_clock);
+
 int drm_connector_set_obj_prop(struct drm_mode_object *obj,
 				    struct drm_property *property,
 				    uint64_t value)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index a66cb4e35d7b..d74e9c64ee88 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;
@@ -2115,6 +2116,10 @@ void drm_connector_attach_privacy_screen_properties(struct drm_connector *conn);
 void drm_connector_attach_privacy_screen_provider(
 	struct drm_connector *connector, struct drm_privacy_screen *priv);
 void drm_connector_update_privacy_screen(const struct drm_connector_state *connector_state);
+unsigned long long
+drm_connector_hdmi_compute_mode_clock(const struct drm_display_mode *mode,
+				      unsigned int bpc,
+				      enum hdmi_colorspace fmt);
 
 /**
  * struct drm_tile_group - Tile group metadata

-- 
2.41.0