drm/bridge: add it6505 driver to read data-lanes and link-frequencies from dt

Add driver to read data-lanes and link-frequencies from dt property to
restrict output bandwidth.
Signed-off-by: allen chen <allen.chen@ite.com.tw>
Signed-off-by: Pin-yen Lin <treapking@chromium.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221103091243.96036-3-allen.chen@ite.com.tw
Link: https://patchwork.freedesktop.org/patch/msgid/20221103091243.96036-2-allen.chen@ite.com.tw
Link: https://patchwork.freedesktop.org/patch/msgid/20221103091243.96036-3-allen.chen@ite.com.tw

drivers/gpu/drm/bridge/ite-it6505.c

@@ -437,6 +437,8 @@ struct it6505 {
 	bool powered;
 	bool hpd_state;
 	u32 afe_setting;
+	u32 max_dpi_pixel_clock;
+	u32 max_lane_count;
 	enum hdcp_state hdcp_status;
 	struct delayed_work hdcp_work;
 	struct work_struct hdcp_wait_ksv_list;
@@ -1464,7 +1466,8 @@ static void it6505_parse_link_capabilities(struct it6505 *it6505)
 	it6505->lane_count = link->num_lanes;
 	DRM_DEV_DEBUG_DRIVER(dev, "Sink support %d lanes training",
 			     it6505->lane_count);
-	it6505->lane_count = min_t(int, it6505->lane_count, MAX_LANE_COUNT);
+	it6505->lane_count = min_t(int, it6505->lane_count,
+				   it6505->max_lane_count);
 
 	it6505->branch_device = drm_dp_is_branch(it6505->dpcd);
 	DRM_DEV_DEBUG_DRIVER(dev, "Sink %sbranch device",
@@ -2907,7 +2910,7 @@ it6505_bridge_mode_valid(struct drm_bridge *bridge,
 	if (mode->flags & DRM_MODE_FLAG_INTERLACE)
 		return MODE_NO_INTERLACE;
 
-	if (mode->clock > DPI_PIXEL_CLK_MAX)
+	if (mode->clock > it6505->max_dpi_pixel_clock)
 		return MODE_CLOCK_HIGH;
 
 	it6505->video_info.clock = mode->clock;
@@ -3096,10 +3099,32 @@ static int it6505_init_pdata(struct it6505 *it6505)
 	return 0;
 }
 
+static int it6505_get_data_lanes_count(const struct device_node *endpoint,
+				       const unsigned int min,
+				       const unsigned int max)
+{
+	int ret;
+
+	ret = of_property_count_u32_elems(endpoint, "data-lanes");
+	if (ret < 0)
+		return ret;
+
+	if (ret < min || ret > max)
+		return -EINVAL;
+
+	return ret;
+}
+
 static void it6505_parse_dt(struct it6505 *it6505)
 {
 	struct device *dev = &it6505->client->dev;
+	struct device_node *np = dev->of_node, *ep = NULL;
+	int len;
+	u64 link_frequencies;
+	u32 data_lanes[4];
 	u32 *afe_setting = &it6505->afe_setting;
+	u32 *max_lane_count = &it6505->max_lane_count;
+	u32 *max_dpi_pixel_clock = &it6505->max_dpi_pixel_clock;
 
 	it6505->lane_swap_disabled =
 		device_property_read_bool(dev, "no-laneswap");
@@ -3115,7 +3140,56 @@ static void it6505_parse_dt(struct it6505 *it6505)
 	} else {
 		*afe_setting = 0;
 	}
-	DRM_DEV_DEBUG_DRIVER(dev, "using afe_setting: %d", *afe_setting);
+
+	ep = of_graph_get_endpoint_by_regs(np, 1, 0);
+	of_node_put(ep);
+
+	if (ep) {
+		len = it6505_get_data_lanes_count(ep, 1, 4);
+
+		if (len > 0 && len != 3) {
+			of_property_read_u32_array(ep, "data-lanes",
+						   data_lanes, len);
+			*max_lane_count = len;
+		} else {
+			*max_lane_count = MAX_LANE_COUNT;
+			dev_err(dev, "error data-lanes, use default");
+		}
+	} else {
+		*max_lane_count = MAX_LANE_COUNT;
+		dev_err(dev, "error endpoint, use default");
+	}
+
+	ep = of_graph_get_endpoint_by_regs(np, 0, 0);
+	of_node_put(ep);
+
+	if (ep) {
+		len = of_property_read_variable_u64_array(ep,
+							  "link-frequencies",
+							  &link_frequencies, 0,
+							  1);
+		if (len >= 0) {
+			do_div(link_frequencies, 1000);
+			if (link_frequencies > 297000) {
+				dev_err(dev,
+					"max pixel clock error, use default");
+				*max_dpi_pixel_clock = DPI_PIXEL_CLK_MAX;
+			} else {
+				*max_dpi_pixel_clock = link_frequencies;
+			}
+		} else {
+			dev_err(dev, "error link frequencies, use default");
+			*max_dpi_pixel_clock = DPI_PIXEL_CLK_MAX;
+		}
+	} else {
+		dev_err(dev, "error endpoint, use default");
+		*max_dpi_pixel_clock = DPI_PIXEL_CLK_MAX;
+	}
+
+	DRM_DEV_DEBUG_DRIVER(dev, "using afe_setting: %u, max_lane_count: %u",
+			     it6505->afe_setting, it6505->max_lane_count);
+	DRM_DEV_DEBUG_DRIVER(dev, "using max_dpi_pixel_clock: %u kHz",
+			     it6505->max_dpi_pixel_clock);
 }
 
 static ssize_t receive_timing_debugfs_show(struct file *file, char __user *buf,