linux-kernel - [PATCH v7 2/2] media: mt9m114: Set pad-slew-rate

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Message-Id: <20250710151340.496218-3-mathis.foerst@mt.com>
Date: Thu, 10 Jul 2025 17:13:40 +0200
From: Mathis Foerst <mathis.foerst@...com>
To: linux-kernel@...r.kernel.org
Cc: Mathis Foerst <mathis.foerst@...com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org,
	manuel.traut@...com,
	mathis.foerst@...hlke.com
Subject: [PATCH v7 2/2] media: mt9m114: Set pad-slew-rate

The MT9M114 supports the different slew rates (0 to 7) on the output pads.
At the moment, this is hardcoded to 7 (the fastest rate).
The user might want to change this values due to EMC requirements.

Read the 'slew-rate' from the DT and configure the pad slew rates of
the output pads accordingly in mt9m114_initialize().
Remove the hardcoded slew rate setting from the mt9m114_init table.

Signed-off-by: Mathis Foerst <mathis.foerst@...com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
---
 drivers/media/i2c/mt9m114.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/media/i2c/mt9m114.c b/drivers/media/i2c/mt9m114.c
index 5f4474d36653..5b84010a2118 100644
--- a/drivers/media/i2c/mt9m114.c
+++ b/drivers/media/i2c/mt9m114.c
@@ -18,6 +18,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/pm_runtime.h>
+#include <linux/property.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/types.h>
@@ -42,6 +43,9 @@
 #define MT9M114_RESET_AND_MISC_CONTROL			CCI_REG16(0x001a)
 #define MT9M114_RESET_SOC					BIT(0)
 #define MT9M114_PAD_SLEW				CCI_REG16(0x001e)
+#define MT9M114_PAD_SLEW_MIN					0
+#define MT9M114_PAD_SLEW_MAX					7
+#define MT9M114_PAD_SLEW_DEFAULT				7
 #define MT9M114_PAD_CONTROL				CCI_REG16(0x0032)
 
 /* XDMA registers */
@@ -388,6 +392,7 @@ struct mt9m114 {
 
 	unsigned int pixrate;
 	bool streaming;
+	u32 pad_slew_rate;
 
 	/* Pixel Array */
 	struct {
@@ -645,9 +650,6 @@ static const struct cci_reg_sequence mt9m114_init[] = {
 	{ MT9M114_CAM_SENSOR_CFG_FINE_INTEG_TIME_MAX,	1459 },
 	{ MT9M114_CAM_SENSOR_CFG_FINE_CORRECTION,	96 },
 	{ MT9M114_CAM_SENSOR_CFG_REG_0_DATA,		32 },
-
-	/* Miscellaneous settings */
-	{ MT9M114_PAD_SLEW,				0x0777 },
 };
 
 /* -----------------------------------------------------------------------------
@@ -779,6 +781,13 @@ static int mt9m114_initialize(struct mt9m114 *sensor)
 	if (ret < 0)
 		return ret;
 
+	value = sensor->pad_slew_rate
+	      | sensor->pad_slew_rate << 4
+	      |	sensor->pad_slew_rate << 8;
+	cci_write(sensor->regmap, MT9M114_PAD_SLEW, value, &ret);
+	if (ret < 0)
+		return ret;
+
 	ret = mt9m114_set_state(sensor, MT9M114_SYS_STATE_ENTER_CONFIG_CHANGE);
 	if (ret < 0)
 		return ret;
@@ -2381,6 +2390,17 @@ static int mt9m114_parse_dt(struct mt9m114 *sensor)
 		goto error;
 	}
 
+	sensor->pad_slew_rate = MT9M114_PAD_SLEW_DEFAULT;
+	device_property_read_u32(&sensor->client->dev, "slew-rate",
+				 &sensor->pad_slew_rate);
+
+	if (sensor->pad_slew_rate < MT9M114_PAD_SLEW_MIN ||
+	    sensor->pad_slew_rate > MT9M114_PAD_SLEW_MAX) {
+		dev_err(&sensor->client->dev, "Invalid slew-rate %u\n",
+			sensor->pad_slew_rate);
+		return -EINVAL;
+	}
+
 	return 0;
 
 error:
-- 
2.34.1