drivers: media: imx708: Adjust broken line correction parameter

In full-resolution mode, the LPF_INTENSITY_EN and LPF_INTENSITY
registers control Quad Bayer Re-mosaic broken line correction.
Expose this as a module parameter "qbc_adjust": zero disables
the correction and values in the range 2 to 5 set its strength.

There is a trade-off between coloured and monochrome patterns.
The previous fixed value 4 could produce ladder/spots artefacts
in coloured textures. The new default value 2 may suit a wider
range of scenes.

Signed-off-by: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>

diff --git a/drivers/media/i2c/imx708.c b/drivers/media/i2c/imx708.c
index 98ab4fc..29b1d44 100644 (file)
--- a/drivers/media/i2c/imx708.c
+++ b/drivers/media/i2c/imx708.c
@@ -20,6 +20,14 @@
 #include <media/v4l2-fwnode.h>
 #include <media/v4l2-mediabus.h>
 
+/*
+ * Parameter to adjust Quad Bayer re-mosaic broken line correction
+ * strength, used in full-resolution mode only. Set zero to disable.
+ */
+static int qbc_adjust = 2;
+module_param(qbc_adjust, int, 0644);
+MODULE_PARM_DESC(qbc_adjust, "Quad Bayer broken line correction strength [0,2-5]");
+
 #define IMX708_REG_VALUE_08BIT         1
 #define IMX708_REG_VALUE_16BIT         2
 
@@ -99,11 +107,17 @@
 
 /* HDR exposure ratio (long:med == med:short) */
 #define IMX708_HDR_EXPOSURE_RATIO       4
-#define IMX708_REG_MID_EXPOSURE        0x3116
-#define IMX708_REG_SHT_EXPOSURE        0x0224
+#define IMX708_REG_MID_EXPOSURE                0x3116
+#define IMX708_REG_SHT_EXPOSURE                0x0224
 #define IMX708_REG_MID_ANALOG_GAIN     0x3118
 #define IMX708_REG_SHT_ANALOG_GAIN     0x0216
 
+/* QBC Re-mosaic broken line correction registers */
+#define IMX708_LPF_INTENSITY_EN                0xC428
+#define IMX708_LPF_INTENSITY_ENABLED   0x00
+#define IMX708_LPF_INTENSITY_DISABLED  0x01
+#define IMX708_LPF_INTENSITY           0xC429
+
 /*
  * Metadata buffer holds a variety of data, all sent with the same VC/DT (0x12).
  * It comprises two scanlines (of up to 5760 bytes each, for 4608 pixels)
@@ -171,6 +185,9 @@ struct imx708_mode {
 
        /* HDR flag, used for checking if the current mode is HDR */
        bool hdr;
+
+       /* Quad Bayer Re-mosaic flag */
+       bool remosaic;
 };
 
 /* Default PDAF pixel correction gains */
@@ -363,8 +380,6 @@ static const struct imx708_reg mode_4608x2592_regs[] = {
        {0x341f, 0x20},
        {0x3420, 0x00},
        {0x3421, 0xd8},
-       {0xC428, 0x00},
-       {0xC429, 0x04},
        {0x3366, 0x00},
        {0x3367, 0x00},
        {0x3368, 0x00},
@@ -677,7 +692,8 @@ static const struct imx708_mode supported_modes_10bit_no_hdr[] = {
                .pixel_rate = 595200000,
                .exposure_lines_min = 8,
                .exposure_lines_step = 1,
-               .hdr = false
+               .hdr = false,
+               .remosaic = true
        },
        {
                /* regular 2x2 binned. */
@@ -699,7 +715,8 @@ static const struct imx708_mode supported_modes_10bit_no_hdr[] = {
                .pixel_rate = 585600000,
                .exposure_lines_min = 4,
                .exposure_lines_step = 2,
-               .hdr = false
+               .hdr = false,
+               .remosaic = false
        },
        {
                /* 2x2 binned and cropped for 720p. */
@@ -721,7 +738,8 @@ static const struct imx708_mode supported_modes_10bit_no_hdr[] = {
                .pixel_rate = 566400000,
                .exposure_lines_min = 4,
                .exposure_lines_step = 2,
-               .hdr = false
+               .hdr = false,
+               .remosaic = false
        },
 };
 
@@ -746,7 +764,8 @@ static const struct imx708_mode supported_modes_10bit_hdr[] = {
                .pixel_rate = 777600000,
                .exposure_lines_min = 8 * IMX708_HDR_EXPOSURE_RATIO * IMX708_HDR_EXPOSURE_RATIO,
                .exposure_lines_step = 2 * IMX708_HDR_EXPOSURE_RATIO * IMX708_HDR_EXPOSURE_RATIO,
-               .hdr = true
+               .hdr = true,
+               .remosaic = false
        }
 };
 
@@ -1515,6 +1534,21 @@ static int imx708_start_streaming(struct imx708 *imx708)
                return ret;
        }
 
+       /* Quad Bayer re-mosaic adjustments (for full-resolution mode only) */
+       if (imx708->mode->remosaic && qbc_adjust > 0) {
+               imx708_write_reg(imx708, IMX708_LPF_INTENSITY,
+                                IMX708_REG_VALUE_08BIT, qbc_adjust);
+               imx708_write_reg(imx708,
+                                IMX708_LPF_INTENSITY_EN,
+                                IMX708_REG_VALUE_08BIT,
+                                IMX708_LPF_INTENSITY_ENABLED);
+       } else {
+               imx708_write_reg(imx708,
+                                IMX708_LPF_INTENSITY_EN,
+                                IMX708_REG_VALUE_08BIT,
+                                IMX708_LPF_INTENSITY_DISABLED);
+       }
+
        /* Apply customized values from user */
        ret =  __v4l2_ctrl_handler_setup(imx708->sd.ctrl_handler);
        if (ret)