linux-kernel - [PATCH v2 2/3] media: i2c: imx219: make HBLANK r/w to allow longer exposures

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Message-Id: <20241121-imx219_fixes-v2-2-7b068a60ea40@ideasonboard.com>
Date: Thu, 21 Nov 2024 17:38:03 +0530
From: Jai Luthra <jai.luthra@...asonboard.com>
To: Dave Stevenson <dave.stevenson@...pberrypi.com>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Jacopo Mondi <jacopo.mondi@...asonboard.com>, 
 Jai Luthra <jai.luthra@...asonboard.com>
Subject: [PATCH v2 2/3] media: i2c: imx219: make HBLANK r/w to allow longer
 exposures

From: Dave Stevenson <dave.stevenson@...pberrypi.com>

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@...pberrypi.com>
Signed-off-by: Jai Luthra <jai.luthra@...asonboard.com>
---
 drivers/media/i2c/imx219.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
index f98aad74fe584a18e2fe7126f92bf294762a54e3..970e6362d0ae3a9078daf337155e83d637bc1ca1 100644
--- a/drivers/media/i2c/imx219.c
+++ b/drivers/media/i2c/imx219.c
@@ -76,8 +76,10 @@
 
 #define IMX219_VBLANK_MIN		32
 
-/* HBLANK control - read only */
-#define IMX219_PPL_DEFAULT		3448
+/* HBLANK control range */
+#define IMX219_PPL_MIN			0x0d78
+#define IMX219_PPL_MAX			0x7ff0
+#define IMX219_REG_HTS			CCI_REG16(0x0162)
 
 #define IMX219_REG_LINE_LENGTH_A	CCI_REG16(0x0162)
 #define IMX219_REG_X_ADD_STA_A		CCI_REG16(0x0164)
@@ -422,6 +424,10 @@ static int imx219_set_ctrl(struct v4l2_ctrl *ctrl)
 		cci_write(imx219->regmap, IMX219_REG_VTS,
 			  format->height + ctrl->val, &ret);
 		break;
+	case V4L2_CID_HBLANK:
+		cci_write(imx219->regmap, IMX219_REG_HTS,
+			  format->width + ctrl->val, &ret);
+		break;
 	case V4L2_CID_TEST_PATTERN_RED:
 		cci_write(imx219->regmap, IMX219_REG_TESTP_RED,
 			  ctrl->val, &ret);
@@ -496,12 +502,10 @@ static int imx219_init_controls(struct imx219 *imx219)
 					   V4L2_CID_VBLANK, IMX219_VBLANK_MIN,
 					   IMX219_VTS_MAX - mode->height, 1,
 					   mode->vts_def - mode->height);
-	hblank = IMX219_PPL_DEFAULT - mode->width;
+	hblank = IMX219_PPL_MIN - mode->width;
 	imx219->hblank = v4l2_ctrl_new_std(ctrl_hdlr, &imx219_ctrl_ops,
 					   V4L2_CID_HBLANK, hblank, hblank,
 					   1, hblank);
-	if (imx219->hblank)
-		imx219->hblank->flags |= V4L2_CTRL_FLAG_READ_ONLY;
 	exposure_max = mode->vts_def - 4;
 	exposure_def = (exposure_max < IMX219_EXPOSURE_DEFAULT) ?
 		exposure_max : IMX219_EXPOSURE_DEFAULT;
@@ -817,6 +821,10 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
 	struct v4l2_mbus_framefmt *format;
 	struct v4l2_rect *crop;
 	unsigned int bin_h, bin_v;
+	u32 prev_hts;
+
+	format = v4l2_subdev_state_get_format(state, 0);
+	prev_hts = format->width + imx219->hblank->val;
 
 	mode = v4l2_find_nearest_size(supported_modes,
 				      ARRAY_SIZE(supported_modes),
@@ -824,8 +832,6 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
 				      fmt->format.width, fmt->format.height);
 
 	imx219_update_pad_format(imx219, mode, &fmt->format, fmt->format.code);
-
-	format = v4l2_subdev_state_get_format(state, 0);
 	*format = fmt->format;
 
 	/*
@@ -861,13 +867,18 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
 					 exposure_max, 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);
 	}
 
 	return 0;

-- 
2.47.0