linux-kernel - Re: [PATCH v6 7/7] media: mt9m114: Set pad-slew-rate

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Message-ID: <aDVdekApG-GT5BHj@kekkonen.localdomain>
Date: Tue, 27 May 2025 06:36:42 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Mathis Foerst <mathis.foerst@...com>
Cc: linux-kernel@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Steve Longerbeam <slongerbeam@...il.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, linux-media@...r.kernel.org,
	devicetree@...r.kernel.org, linux-staging@...ts.linux.dev,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	manuel.traut@...com, mathis.foerst@...hlke.com
Subject: Re: [PATCH v6 7/7] media: mt9m114: Set pad-slew-rate

Hi Mathis,

On Thu, May 22, 2025 at 04:35:11PM +0200, Mathis Foerst wrote:
> 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 9ff46c72dbc1..f3f9ecc0866c 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 {
> @@ -650,9 +655,6 @@ 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 },
>  };
>  
>  /* -----------------------------------------------------------------------------
> @@ -784,6 +786,13 @@ 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;

Please drop the redundant parentheses.

> +	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;
> @@ -2398,6 +2407,17 @@ 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:

-- 
Sakari Ailus