media: i2c: ov9282: Add selection for CSI2 clock mode

The sensor supports either having the CSI2 clock lane free
running, or gated when there is no packet to transmit.
The driver only selected gated (non-continuous) clock mode.

Add code to allow fwnode to configure whether the clock is
gated or free running.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/i2c/ov9282.c

@@ -45,6 +45,9 @@
 /* Group hold register */
 #define OV9282_REG_HOLD		0x3308
 
+#define OV9282_REG_MIPI_CTRL00	0x4800
+#define OV9282_GATED_CLOCK	BIT(5)
+
 /* Input clock rate */
 #define OV9282_INCLK_RATE	24000000
 
@@ -136,6 +139,7 @@ struct ov9282 {
 		struct v4l2_ctrl *again_ctrl;
 	};
 	u32 vblank;
+	bool noncontinuous_clock;
 	const struct ov9282_mode *cur_mode;
 	struct mutex mutex;
 	bool streaming;
@@ -145,7 +149,13 @@ static const s64 link_freq[] = {
 	OV9282_LINK_FREQ,
 };
 
-/* Common registers */
+/*
+ * Common registers
+ *
+ * Note: Do NOT include a software reset (0x0103, 0x01) in any of these
+ * register arrays as some settings are written as part of ov9282_power_on,
+ * and the reset will clear them.
+ */
 static const struct ov9282_reg common_regs[] = {
 	{0x0302, 0x32},
 	{0x030d, 0x50},
@@ -201,7 +211,6 @@ static const struct ov9282_reg common_regs[] = {
 	{0x4601, 0x04},
 	{0x470f, 0x00},
 	{0x4f07, 0x00},
-	{0x4800, 0x20},
 	{0x5000, 0x9f},
 	{0x5001, 0x00},
 	{0x5e00, 0x00},
@@ -835,6 +844,9 @@ static int ov9282_parse_hw_config(struct ov9282 *ov9282)
 	if (ret)
 		return ret;
 
+	ov9282->noncontinuous_clock =
+		bus_cfg.bus.mipi_csi2.flags & V4L2_MBUS_CSI2_NONCONTINUOUS_CLOCK;
+
 	if (bus_cfg.bus.mipi_csi2.num_data_lanes != OV9282_NUM_DATA_LANES) {
 		dev_err(ov9282->dev,
 			"number of CSI2 data lanes %d is not supported",
@@ -903,6 +915,14 @@ static int ov9282_power_on(struct device *dev)
 
 	usleep_range(400, 600);
 
+	ret = ov9282_write_reg(ov9282, OV9282_REG_MIPI_CTRL00, 1,
+			       ov9282->noncontinuous_clock ?
+					OV9282_GATED_CLOCK : 0);
+	if (ret) {
+		dev_err(ov9282->dev, "fail to write MIPI_CTRL00");
+		return ret;
+	}
+
 	return 0;
 
 error_reset: