media: i2c: imx477: Add support for adaptive frame control

Use V4L2_CID_EXPOSURE_AUTO_PRIORITY to control if the driver should
automatically adjust the sensor frame length based on exposure time,
allowing variable frame rates and longer exposures.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>

diff --git a/drivers/media/i2c/imx477.c b/drivers/media/i2c/imx477.c
index ec56b0c..bd0e2c2 100644 (file)
--- a/drivers/media/i2c/imx477.c
+++ b/drivers/media/i2c/imx477.c
@@ -1082,6 +1082,8 @@ struct imx477 {
        struct v4l2_ctrl *hflip;
        struct v4l2_ctrl *vblank;
        struct v4l2_ctrl *hblank;
+       /* This ctrl allows automatic variable framerate */
+       struct v4l2_ctrl *exposure_auto;
 
        /* Current mode */
        const struct imx477_mode *mode;
@@ -1278,6 +1280,72 @@ static int imx477_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
        return 0;
 }
 
+static int imx477_set_exposure(struct imx477 *imx477, unsigned int val)
+{
+       int ret;
+
+       ret = imx477_write_reg(imx477, IMX477_REG_EXPOSURE,
+                              IMX477_REG_VALUE_16BIT, val);
+
+       /* Setup the frame length in the case of auto framerate mode. */
+       if (imx477->exposure_auto->val) {
+               unsigned int frame_length, frame_length_max, frame_length_min;
+
+               frame_length_min = imx477->vblank->minimum +
+                                  imx477->mode->height;
+               frame_length_max = imx477->vblank->maximum +
+                                  imx477->mode->height;
+               frame_length = max(frame_length_min,
+                                  val + IMX477_EXPOSURE_OFFSET);
+               frame_length = min(frame_length_max, frame_length);
+               ret += imx477_write_reg(imx477, IMX477_REG_FRAME_LENGTH,
+                                       IMX477_REG_VALUE_16BIT, frame_length);
+       }
+
+       return ret;
+}
+
+static void imx477_adjust_exposure_range(struct imx477 *imx477,
+                                        struct v4l2_ctrl *ctrl)
+{
+       int exposure_max, exposure_def;
+
+       if (ctrl->id == V4L2_CID_VBLANK || !ctrl->val) {
+               /*
+                * Either VBLANK has been changed or auto framerate
+                * adjusting has been disabled. Honour the VBLANK limits
+                * when setting exposure.
+                */
+               exposure_max = imx477->mode->height + imx477->vblank->val -
+                                                     IMX477_EXPOSURE_OFFSET;
+
+               if (ctrl->id == V4L2_CID_EXPOSURE_AUTO_PRIORITY) {
+                       /*
+                        * Allow VBLANK adjustments since the driver is not
+                        * handling frame length control automatically.
+                        */
+                       __v4l2_ctrl_grab(imx477->vblank, false);
+               }
+       } else {
+               /*
+                * Auto framerate adjusting has been enabled. VBLANK
+                * ctrl has been disabled and exposure can ramp up
+                * to the maximum allowable value.
+                */
+               exposure_max = IMX477_EXPOSURE_MAX;
+               /*
+                * Do not allow VBLANK adjustments if the driver is
+                * handling it frame length control automatically.
+                */
+               __v4l2_ctrl_grab(imx477->vblank, true);
+       }
+
+       exposure_def = min(exposure_max, imx477->exposure->val);
+       __v4l2_ctrl_modify_range(imx477->exposure, imx477->exposure->minimum,
+                                exposure_max, imx477->exposure->step,
+                                exposure_def);
+}
+
 static int imx477_set_ctrl(struct v4l2_ctrl *ctrl)
 {
        struct imx477 *imx477 =
@@ -1285,17 +1353,13 @@ static int imx477_set_ctrl(struct v4l2_ctrl *ctrl)
        struct i2c_client *client = v4l2_get_subdevdata(&imx477->sd);
        int ret = 0;
 
-       if (ctrl->id == V4L2_CID_VBLANK) {
-               int exposure_max, exposure_def;
-
-               /* Update max exposure while meeting expected vblanking */
-               exposure_max = imx477->mode->height + ctrl->val -
-                                                       IMX477_EXPOSURE_OFFSET;
-               exposure_def = min(exposure_max, imx477->exposure->val);
-               __v4l2_ctrl_modify_range(imx477->exposure,
-                                        imx477->exposure->minimum,
-                                        exposure_max, imx477->exposure->step,
-                                        exposure_def);
+       if (ctrl->id == V4L2_CID_VBLANK ||
+           ctrl->id == V4L2_CID_EXPOSURE_AUTO_PRIORITY) {
+               /*
+                * These controls may change the limits of usable exposure,
+                * so check and adjust if necessary.
+                */
+               imx477_adjust_exposure_range(imx477, ctrl);
        }
 
        /*
@@ -1311,8 +1375,14 @@ static int imx477_set_ctrl(struct v4l2_ctrl *ctrl)
                                       IMX477_REG_VALUE_16BIT, ctrl->val);
                break;
        case V4L2_CID_EXPOSURE:
-               ret = imx477_write_reg(imx477, IMX477_REG_EXPOSURE,
-                                      IMX477_REG_VALUE_16BIT, ctrl->val);
+               ret = imx477_set_exposure(imx477, ctrl->val);
+               break;
+       case V4L2_CID_EXPOSURE_AUTO_PRIORITY:
+               /*
+                * imx477_set_exposure() will recalculate the frame length
+                * to adjust the framerate to match the exposure.
+                */
+               ret = imx477_set_exposure(imx477, imx477->exposure->val);
                break;
        case V4L2_CID_DIGITAL_GAIN:
                ret = imx477_write_reg(imx477, IMX477_REG_DIGITAL_GAIN,
@@ -1510,9 +1580,8 @@ unsigned int imx477_get_frame_length(const struct imx477_mode *mode,
 
 static void imx477_set_framing_limits(struct imx477 *imx477)
 {
+       unsigned int frm_length_min, frm_length_default, hblank;
        const struct imx477_mode *mode = imx477->mode;
-       unsigned int frm_length_min, frm_length_default;
-       unsigned int exposure_max, exposure_def, hblank;
 
        frm_length_min = imx477_get_frame_length(mode, &mode->timeperframe_min);
        frm_length_default =
@@ -1522,15 +1591,10 @@ static void imx477_set_framing_limits(struct imx477 *imx477)
        __v4l2_ctrl_modify_range(imx477->vblank, frm_length_min - mode->height,
                                 IMX477_FRAME_LENGTH_MAX - mode->height,
                                 1, frm_length_default - mode->height);
+
+       /* Setting this will adjust the exposure limits as well. */
        __v4l2_ctrl_s_ctrl(imx477->vblank, frm_length_default - mode->height);
 
-       /* Update max exposure while meeting expected vblanking */
-       exposure_max = IMX477_FRAME_LENGTH_MAX - IMX477_EXPOSURE_OFFSET;
-       exposure_def = frm_length_default - mode->height -
-                                           IMX477_EXPOSURE_OFFSET;
-       __v4l2_ctrl_modify_range(imx477->exposure, imx477->exposure->minimum,
-                                exposure_max, imx477->exposure->step,
-                                exposure_def);
        /*
         * Currently PPL is fixed to the mode specified value, so hblank
         * depends on mode->width only, and is not changeable in any
@@ -1939,6 +2003,11 @@ static int imx477_init_controls(struct imx477 *imx477)
                          IMX477_DGTL_GAIN_MIN, IMX477_DGTL_GAIN_MAX,
                          IMX477_DGTL_GAIN_STEP, IMX477_DGTL_GAIN_DEFAULT);
 
+       imx477->exposure_auto =
+                       v4l2_ctrl_new_std(ctrl_hdlr, &imx477_ctrl_ops,
+                                         V4L2_CID_EXPOSURE_AUTO_PRIORITY,
+                                         0, 1, 1, 0);
+
        imx477->hflip = v4l2_ctrl_new_std(ctrl_hdlr, &imx477_ctrl_ops,
                                          V4L2_CID_HFLIP, 0, 1, 1, 0);
        if (imx477->hflip)