[PATCHv3 5/5] drm: exynos: hdmi: add support for pixel clock limitation

[Tomasz Stanislawski]

Adds support for limitation of maximal pixel clock of HDMI
signal. This feature is needed on boards that contains
lines or bridges with frequency limitations.

Signed-off-by: Tomasz Stanislawski <t.stanislaws at samsung.com>
---
 .../devicetree/bindings/video/exynos_hdmi.txt      |    4 ++++
 drivers/gpu/drm/exynos/exynos_hdmi.c               |   11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/Documentation/devicetree/bindings/video/exynos_hdmi.txt b/Documentation/devicetree/bindings/video/exynos_hdmi.txt
index f9187a2..8718f8d 100644
--- a/Documentation/devicetree/bindings/video/exynos_hdmi.txt
+++ b/Documentation/devicetree/bindings/video/exynos_hdmi.txt
@@ -28,6 +28,10 @@ Required properties:
 - ddc: phandle to the hdmi ddc node
 - phy: phandle to the hdmi phy node
 
+Optional properties:
+- max-pixel-clock: used to limit the maximal pixel clock if a board has lines,
+	connectors or bridges not capable of carring higher frequencies
+
 Example:
 
 	hdmi {
diff --git a/drivers/gpu/drm/exynos/exynos_hdmi.c b/drivers/gpu/drm/exynos/exynos_hdmi.c
index 9adbd34..e012ba9 100644
--- a/drivers/gpu/drm/exynos/exynos_hdmi.c
+++ b/drivers/gpu/drm/exynos/exynos_hdmi.c
@@ -194,6 +194,7 @@ struct hdmi_context {
 	struct hdmi_resources		res;
 
 	int				hpd_gpio;
+	u32				max_pixel_clock;
 
 	enum hdmi_type			type;
 };
@@ -886,6 +887,9 @@ static int hdmi_mode_valid(struct drm_connector *connector,
 	if (ret)
 		return MODE_BAD;
 
+	if (mode->clock * 1000 > hdata->max_pixel_clock)
+		return MODE_CLOCK_HIGH;
+
 	ret = hdmi_find_phy_conf(hdata, mode->clock * 1000);
 	if (ret < 0)
 		return MODE_BAD;
@@ -2022,6 +2026,13 @@ static int drm_hdmi_dt_parse(struct hdmi_context *hdata, struct device_node *np)
 		return -ENOENT;
 	}
 
+	of_property_read_u32(np, "max-pixel-clock", &hdata->max_pixel_clock);
+	if (!hdata->max_pixel_clock) {
+		DRM_INFO("max-pixel-clock is zero, using INF\n");
+		hdata->max_pixel_clock = U32_MAX;
+	}
+
+
 	return 0;
 }
 
-- 
1.7.9.5