media: i2c: max9286: Support manual framesync operation

The MAX9286 can generate a framesync signal to synchronize the cameras,
using an internal timer. Support this mode of operation and configure it
through the .s_frameinterval() operation. If the frame interval is not
0, framesync is switched to manual mode with the specified interval,
otherwise automatic mode is used.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/i2c/max9286.c

@@ -174,9 +174,11 @@ struct max9286_priv {
 	u32 gpio_poc[2];
 
 	struct v4l2_ctrl_handler ctrls;
-	struct v4l2_ctrl *pixelrate;
+	struct v4l2_ctrl *pixelrate_ctrl;
+	unsigned int pixelrate;
 
 	struct v4l2_mbus_framefmt fmt[MAX9286_N_SINKS];
+	struct v4l2_fract interval;
 
 	/* Protects controls and fmt structures */
 	struct mutex mutex;
@@ -477,6 +479,40 @@ static int max9286_check_config_link(struct max9286_priv *priv,
 	return 0;
 }
 
+static void max9286_set_fsync_period(struct max9286_priv *priv)
+{
+	u32 fsync;
+
+	if (!priv->interval.numerator || !priv->interval.denominator) {
+		/*
+		 * Special case, a null interval enables automatic FRAMESYNC
+		 * mode. FRAMESYNC is taken from the slowest link.
+		 */
+		max9286_write(priv, 0x01, MAX9286_FSYNCMODE_INT_HIZ |
+			      MAX9286_FSYNCMETH_AUTO);
+		return;
+	}
+
+	/*
+	 * Manual FRAMESYNC
+	 *
+	 * The FRAMESYNC generator is configured with a period expressed as a
+	 * number of PCLK periods.
+	 */
+	fsync = div_u64((u64)priv->pixelrate * priv->interval.numerator,
+			priv->interval.denominator);
+
+	dev_dbg(&priv->client->dev, "fsync period %u (pclk %u)\n", fsync,
+		priv->pixelrate);
+
+	max9286_write(priv, 0x01, MAX9286_FSYNCMODE_INT_OUT |
+		      MAX9286_FSYNCMETH_MANUAL);
+
+	max9286_write(priv, 0x06, (fsync >> 0) & 0xff);
+	max9286_write(priv, 0x07, (fsync >> 8) & 0xff);
+	max9286_write(priv, 0x08, (fsync >> 16) & 0xff);
+}
+
 /* -----------------------------------------------------------------------------
  * V4L2 Subdev
  */
@@ -515,11 +551,13 @@ static int max9286_set_pixelrate(struct max9286_priv *priv)
 		return -EINVAL;
 	}
 
+	priv->pixelrate = pixelrate;
+
 	/*
 	 * The CSI-2 transmitter pixel rate is the single source rate multiplied
 	 * by the number of available sources.
 	 */
-	return v4l2_ctrl_s_ctrl_int64(priv->pixelrate,
+	return v4l2_ctrl_s_ctrl_int64(priv->pixelrate_ctrl,
 				      pixelrate * priv->nsources);
 }
 
@@ -659,6 +697,8 @@ static int max9286_s_stream(struct v4l2_subdev *sd, int enable)
 	int ret;
 
 	if (enable) {
+		max9286_set_fsync_period(priv);
+
 		/*
 		 * The frame sync between cameras is transmitted across the
 		 * reverse channel as GPIO. We must open all channels while
@@ -718,6 +758,32 @@ static int max9286_s_stream(struct v4l2_subdev *sd, int enable)
 	return 0;
 }
 
+static int max9286_g_frame_interval(struct v4l2_subdev *sd,
+				    struct v4l2_subdev_frame_interval *interval)
+{
+	struct max9286_priv *priv = sd_to_max9286(sd);
+
+	if (interval->pad != MAX9286_SRC_PAD)
+		return -EINVAL;
+
+	interval->interval = priv->interval;
+
+	return 0;
+}
+
+static int max9286_s_frame_interval(struct v4l2_subdev *sd,
+				    struct v4l2_subdev_frame_interval *interval)
+{
+	struct max9286_priv *priv = sd_to_max9286(sd);
+
+	if (interval->pad != MAX9286_SRC_PAD)
+		return -EINVAL;
+
+	priv->interval = interval->interval;
+
+	return 0;
+}
+
 static int max9286_enum_mbus_code(struct v4l2_subdev *sd,
 				  struct v4l2_subdev_state *sd_state,
 				  struct v4l2_subdev_mbus_code_enum *code)
@@ -809,6 +875,8 @@ static int max9286_get_fmt(struct v4l2_subdev *sd,
 
 static const struct v4l2_subdev_video_ops max9286_video_ops = {
 	.s_stream	= max9286_s_stream,
+	.g_frame_interval = max9286_g_frame_interval,
+	.s_frame_interval = max9286_s_frame_interval,
 };
 
 static const struct v4l2_subdev_pad_ops max9286_pad_ops = {
@@ -893,10 +961,10 @@ static int max9286_v4l2_register(struct max9286_priv *priv)
 	priv->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
 
 	v4l2_ctrl_handler_init(&priv->ctrls, 1);
-	priv->pixelrate = v4l2_ctrl_new_std(&priv->ctrls,
-					    &max9286_ctrl_ops,
-					    V4L2_CID_PIXEL_RATE,
-					    1, INT_MAX, 1, 50000000);
+	priv->pixelrate_ctrl = v4l2_ctrl_new_std(&priv->ctrls,
+						 &max9286_ctrl_ops,
+						 V4L2_CID_PIXEL_RATE,
+						 1, INT_MAX, 1, 50000000);
 
 	priv->sd.ctrl_handler = &priv->ctrls;
 	ret = priv->ctrls.error;
@@ -1006,9 +1074,7 @@ static int max9286_setup(struct max9286_priv *priv)
 		      MAX9286_CSILANECNT(priv->csi2_data_lanes) |
 		      MAX9286_DATATYPE_YUV422_8BIT);
 
-	/* Automatic: FRAMESYNC taken from the slowest Link. */
-	max9286_write(priv, 0x01, MAX9286_FSYNCMODE_INT_HIZ |
-		      MAX9286_FSYNCMETH_AUTO);
+	max9286_set_fsync_period(priv);
 
 	/* Enable HS/VS encoding, use D14/15 for HS/VS, invert VS. */
 	max9286_write(priv, 0x0c, MAX9286_HVEN | MAX9286_INVVS |