media: ov9282: Add external trigger mode support

arch/arm/boot/dts/overlays/README

@@ -3718,6 +3718,10 @@ Params: rotation                Mounting rotation of the camera sensor (0 or
         clk-continuous          Switch to continuous mode on the CSI clock lane,
                                 which increases the maximum frame rate slightly.
                                 Appears not to work on Pi3.
+        trigger-mode            Enable external trigger mode (0 = normal,
+                                1 = triggered). In this mode, the sensor outputs
+                                a frame only when triggered by a rising edge
+                                on the FSIN input pin.
 
 
 Name:   papirus

arch/arm/boot/dts/overlays/ov9281-overlay.dts

@@ -95,7 +95,8 @@
 		       <&cam_node>, "avdd-supply:0=",<&cam0_reg>,
 		       <&reg_frag>, "target:0=",<&cam0_reg>;
 		arducam = <0>, "+6";
 		clk-continuous = <0>, "-7-8";
+                trigger-mode = <&cam_node>, "trigger-mode:0";
 	};
 };
 

arch/arm/boot/dts/overlays/ov9281.dtsi

@@ -14,6 +14,7 @@ cam_node: ov9281@60 {
 
 	rotation = <0>;
 	orientation = <2>;
+	trigger-mode = <0>;
 
 	port {
 		cam_endpoint: endpoint {

drivers/media/i2c/ov9282.c

@@ -65,6 +65,14 @@
 #define OV9282_REG_MIPI_CTRL00	0x4800
 #define OV9282_GATED_CLOCK	BIT(5)
 
+/* Trigger mode registers */
+#define OV9282_REG_POWER_CTRL 0x4F00
+#define OV9282_REG_LOW_POWER_MODE_CTRL 0x3030
+#define OV9282_REG_NUM_FRAME_ON_TRIG 0x303F
+#define OV9282_REG_SLEEP_PERIOD_CTRL0 0x302C
+#define OV9282_REG_SLEEP_PERIOD_CTRL3 0x302F
+#define OV9282_REG_TIMING_23 0x3823
+
 /* Input clock rate */
 #define OV9282_INCLK_RATE	24000000
 
@@ -187,6 +195,7 @@
 	const struct ov9282_mode *cur_mode;
 	u32 code;
 	struct mutex mutex;
+	int trigger_mode;
 };
 
 static const s64 link_freq[] = {
@@ -947,6 +956,65 @@
 	return -EINVAL;
 }
 
+/**
+ * ov9282_apply_trigger_config() - Configure sensor for FSIN external trigger mode
+ * @ov9282: pointer to ov9282 device
+ *
+ * Return: 0 on success, error code otherwise.
+ */
+static int ov9282_apply_trigger_config(struct ov9282 *ov9282)
+{
+        int ret;
+
+        ret = ov9282_write_reg(ov9282, OV9282_REG_MODE_SELECT, 1, OV9282_MODE_STANDBY);
+        if (ret) {
+                return ret;
+        }
+
+	/* Low power mode */
+        ret = ov9282_write_reg(ov9282, OV9282_REG_POWER_CTRL, 1, 0x01);
+        if (ret) {
+                return ret;
+        }
+
+	/* External trigger snapshot */
+        ret = ov9282_write_reg(ov9282, OV9282_REG_LOW_POWER_MODE_CTRL, 1, 0x04);
+        if (ret) {
+                return ret;
+        }
+
+	/* 1 frame per trigger */
+        ov9282_write_reg(ov9282, OV9282_REG_NUM_FRAME_ON_TRIG, 1, 0x01);
+        if (ret) {
+                return ret;
+        }
+
+        ov9282_write_reg(ov9282, OV9282_REG_SLEEP_PERIOD_CTRL0, 1, 0x00);
+        if (ret) {
+                return ret;
+        }
+
+        ov9282_write_reg(ov9282, OV9282_REG_SLEEP_PERIOD_CTRL3, 1, 0x7F);
+        if (ret) {
+                return ret;
+        }
+
+	/* No auto wake */
+        ov9282_write_reg(ov9282, OV9282_REG_TIMING_23, 1, 0x00);
+        if (ret) {
+                return ret;
+        }
+
+        /* stay standby mode and wait for trigger signal */
+        ret = ov9282_write_reg(ov9282, OV9282_REG_MODE_SELECT,
+                        1, OV9282_MODE_STANDBY);
+        if (ret) {
+                return ret;
+        }
+
+	return 0;
+}
+
 /**
  * ov9282_start_streaming() - Start sensor stream
  * @ov9282: pointer to ov9282 device
@@ -970,7 +1038,7 @@
 
 	/* Write common registers */
 	ret = ov9282_write_regs(ov9282, common_regs_list.regs,
-				common_regs_list.num_of_regs);
+			       common_regs_list.num_of_regs);
 	if (ret) {
 		dev_err(ov9282->dev, "fail to write common registers");
 		return ret;
@@ -992,15 +1060,25 @@
 	}
 
 	/* Setup handler will write actual exposure and gain */
-	ret =  __v4l2_ctrl_handler_setup(ov9282->sd.ctrl_handler);
+	ret = __v4l2_ctrl_handler_setup(ov9282->sd.ctrl_handler);
 	if (ret) {
 		dev_err(ov9282->dev, "fail to setup handler");
 		return ret;
 	}
 
+	if (ov9282->trigger_mode > 0) {
+ 		/* Configure FSIN external trigger mode */
+		ret = ov9282_apply_trigger_config(ov9282);
+		if (ret) {
+			dev_err(ov9282->dev, "failed to config external trigger mode");
+			return ret;
+		}
+		return 0;
+	}
+
 	/* Start streaming */
 	ret = ov9282_write_reg(ov9282, OV9282_REG_MODE_SELECT,
-			       1, OV9282_MODE_STREAMING);
+			1, OV9282_MODE_STREAMING);
 	if (ret) {
 		dev_err(ov9282->dev, "fail to start streaming");
 		return ret;
@@ -1392,6 +1470,7 @@
 {
 	struct ov9282 *ov9282;
 	int ret;
+	u32 trig_mod;
 
 	ov9282 = devm_kzalloc(&client->dev, sizeof(*ov9282), GFP_KERNEL);
 	if (!ov9282)
@@ -1431,6 +1510,9 @@
 	ov9282->code = MEDIA_BUS_FMT_Y10_1X10;
 	ov9282->vblank = ov9282->cur_mode->vblank;
 
+	ret = of_property_read_u32(client->dev.of_node, "trigger-mode", &trig_mod);
+	ov9282->trigger_mode = (ret == 0) ? trig_mod : -1;
+
 	ret = ov9282_init_controls(ov9282);
 	if (ret) {
 		dev_err(ov9282->dev, "failed to init controls: %d", ret);