From 155b736f0ff883415d374ba743473f5ef146814b Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Wed, 21 Sep 2022 14:10:42 +0100
Subject: [PATCH] media: i2c: imx219: make HBLANK r/w to allow longer exposures

The HBLANK control was read-only, and always configured such
that the sensor HTS register was 3448. This limited the maximum
exposure time that could be achieved to around 1.26 secs.

Make HBLANK read/write so that the line time can be extended,
and thereby allow longer exposures (and slower frame rates).
Retain the overall HTS setting when changing modes rather than
resetting it to a default.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
 drivers/media/i2c/imx219.c | 47 ++++++++++++++++++++++++++--------------------
 1 file changed, 27 insertions(+), 20 deletions(-)

diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
index 4339ddc..185596e 100644
--- a/drivers/media/i2c/imx219.c
+++ b/drivers/media/i2c/imx219.c
@@ -63,8 +63,10 @@
 #define IMX219_FLL_STEP			1
 #define IMX219_FLL_DEFAULT		0x0c98
 
-/* HBLANK control - read only */
-#define IMX219_PPL_DEFAULT		3448
+/* HBLANK control range */
+#define IMX219_PPL_MIN			3448
+#define IMX219_PPL_MAX			0x7ff0
+#define IMX219_REG_HTS			0x0162
 
 /* Exposure control */
 #define IMX219_REG_EXPOSURE		0x015a
@@ -216,8 +218,6 @@ static const struct imx219_reg mode_3280x2464_regs[] = {
 	{0x4793, 0x10},
 	{0x4797, 0x0e},
 	{0x479b, 0x0e},
-	{0x0162, 0x0d},
-	{0x0163, 0x78},
 };
 
 static const struct imx219_reg mode_1920_1080_regs[] = {
@@ -232,8 +232,6 @@ static const struct imx219_reg mode_1920_1080_regs[] = {
 	{0x0128, 0x00},
 	{0x012a, 0x18},
 	{0x012b, 0x00},
-	{0x0162, 0x0d},
-	{0x0163, 0x78},
 	{0x0164, 0x02},
 	{0x0165, 0xa8},
 	{0x0166, 0x0a},
@@ -330,8 +328,6 @@ static const struct imx219_reg mode_1640_1232_regs[] = {
 	{0x4793, 0x10},
 	{0x4797, 0x0e},
 	{0x479b, 0x0e},
-	{0x0162, 0x0d},
-	{0x0163, 0x78},
 };
 
 static const struct imx219_reg mode_640_480_regs[] = {
@@ -346,8 +342,6 @@ static const struct imx219_reg mode_640_480_regs[] = {
 	{0x0128, 0x00},
 	{0x012a, 0x18},
 	{0x012b, 0x00},
-	{0x0162, 0x0d},
-	{0x0163, 0x78},
 	{0x0164, 0x03},
 	{0x0165, 0xe8},
 	{0x0166, 0x08},
@@ -800,6 +794,11 @@ static int imx219_set_ctrl(struct v4l2_ctrl *ctrl)
 				       (imx219->mode->height + ctrl->val) /
 						imx219->mode->rate_factor);
 		break;
+	case V4L2_CID_HBLANK:
+		ret = imx219_write_reg(imx219, IMX219_REG_HTS,
+				       IMX219_REG_VALUE_16BIT,
+				       imx219->mode->width + ctrl->val);
+		break;
 	case V4L2_CID_TEST_PATTERN_RED:
 		ret = imx219_write_reg(imx219, IMX219_REG_TESTP_RED,
 				       IMX219_REG_VALUE_16BIT, ctrl->val);
@@ -1000,6 +999,8 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
 			*framefmt = fmt->format;
 		} else if (imx219->mode != mode ||
 			imx219->fmt.code != fmt->format.code) {
+			u32 prev_hts = imx219->mode->width + imx219->hblank->val;
+
 			imx219->fmt = fmt->format;
 			imx219->mode = mode;
 			/* Update limits and set FPS to default */
@@ -1024,13 +1025,19 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
 						 imx219->exposure->step,
 						 exposure_def);
 			/*
-			 * Currently PPL is fixed to IMX219_PPL_DEFAULT, so
-			 * hblank depends on mode->width only, and is not
-			 * changeble in any way other than changing the mode.
+			 * Retain PPL setting from previous mode so that the
+			 * line time does not change on a mode change.
+			 * Limits have to be recomputed as the controls define
+			 * the blanking only, so PPL values need to have the
+			 * mode width subtracted.
 			 */
-			hblank = IMX219_PPL_DEFAULT - mode->width;
-			__v4l2_ctrl_modify_range(imx219->hblank, hblank, hblank,
-						 1, hblank);
+			hblank = prev_hts - mode->width;
+			__v4l2_ctrl_modify_range(imx219->hblank,
+						 IMX219_PPL_MIN - mode->width,
+						 IMX219_PPL_MAX - mode->width,
+						 1,
+						 IMX219_PPL_MIN - mode->width);
+			__v4l2_ctrl_s_ctrl(imx219->hblank, hblank);
 
 			/* Scale the pixel rate based on the mode specific factor */
 			pixel_rate =
@@ -1412,12 +1419,12 @@ static int imx219_init_controls(struct imx219 *imx219)
 					   V4L2_CID_VBLANK, IMX219_VBLANK_MIN,
 					   IMX219_VTS_MAX - height, 1,
 					   imx219->mode->vts_def - height);
-	hblank = IMX219_PPL_DEFAULT - imx219->mode->width;
+	hblank = IMX219_PPL_MIN - imx219->mode->width;
 	imx219->hblank = v4l2_ctrl_new_std(ctrl_hdlr, &imx219_ctrl_ops,
-					   V4L2_CID_HBLANK, hblank, hblank,
+					   V4L2_CID_HBLANK, hblank,
+					   IMX219_PPL_MAX - imx219->mode->width,
 					   1, hblank);
-	if (imx219->hblank)
-		imx219->hblank->flags |= V4L2_CTRL_FLAG_READ_ONLY;
+
 	exposure_max = imx219->mode->vts_def - 4;
 	exposure_def = (exposure_max < IMX219_EXPOSURE_DEFAULT) ?
 		exposure_max : IMX219_EXPOSURE_DEFAULT;
-- 
2.7.4