linux-kernel - Re: [PATCH 1/4] media: mt9m111: add V4L2_CID_PIXEL

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Message-ID: <20220818161108.dlmi77o6j7wcyayc@uno.localdomain>
Date:   Thu, 18 Aug 2022 18:11:08 +0200
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     mchehab@...nel.org, sakari.ailus@...ux.intel.com,
        laurent.pinchart+renesas@...asonboard.com,
        jacopo+renesas@...ndi.org, akinobu.mita@...il.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de
Subject: Re: [PATCH 1/4] media: mt9m111: add V4L2_CID_PIXEL_RATE support

Hi Marco

On Thu, Aug 18, 2022 at 04:47:09PM +0200, Marco Felsch wrote:
> Add support to report the PIXEL_RATE so a host or bridge device can ask
> the sensor.
>
> Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> ---
>  drivers/media/i2c/mt9m111.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/i2c/mt9m111.c b/drivers/media/i2c/mt9m111.c
> index afc86efa9e3e..cdaf283e1309 100644
> --- a/drivers/media/i2c/mt9m111.c
> +++ b/drivers/media/i2c/mt9m111.c
> @@ -908,6 +908,8 @@ static int mt9m111_s_ctrl(struct v4l2_ctrl *ctrl)
>  		return mt9m111_set_test_pattern(mt9m111, ctrl->val);
>  	case V4L2_CID_COLORFX:
>  		return mt9m111_set_colorfx(mt9m111, ctrl->val);
> +	case V4L2_CID_PIXEL_RATE:
> +		return 0;

By default PIXEL_RATE is read-only.
Do you get a call to s_ctrl for it ?

>  	}
>
>  	return -EINVAL;
> @@ -1249,6 +1251,7 @@ static int mt9m111_probe(struct i2c_client *client)
>  {
>  	struct mt9m111 *mt9m111;
>  	struct i2c_adapter *adapter = client->adapter;
> +	unsigned long mclk_rate;
>  	int ret;
>
>  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WORD_DATA)) {
> @@ -1271,6 +1274,13 @@ static int mt9m111_probe(struct i2c_client *client)
>  	if (IS_ERR(mt9m111->clk))
>  		return PTR_ERR(mt9m111->clk);
>
> +	ret = clk_prepare_enable(mt9m111->clk);
> +	if (ret < 0)
> +		return ret;
> +

Do you need to enable clock to read its rate ?

> +	mclk_rate = clk_get_rate(mt9m111->clk);
> +	clk_disable_unprepare(mt9m111->clk);
> +
>  	mt9m111->regulator = devm_regulator_get(&client->dev, "vdd");
>  	if (IS_ERR(mt9m111->regulator)) {
>  		dev_err(&client->dev, "regulator not found: %ld\n",
> @@ -1285,7 +1295,7 @@ static int mt9m111_probe(struct i2c_client *client)
>  	mt9m111->subdev.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE |
>  				 V4L2_SUBDEV_FL_HAS_EVENTS;
>
> -	v4l2_ctrl_handler_init(&mt9m111->hdl, 7);
> +	v4l2_ctrl_handler_init(&mt9m111->hdl, 8);
>  	v4l2_ctrl_new_std(&mt9m111->hdl, &mt9m111_ctrl_ops,
>  			V4L2_CID_VFLIP, 0, 1, 1, 0);
>  	v4l2_ctrl_new_std(&mt9m111->hdl, &mt9m111_ctrl_ops,
> @@ -1309,6 +1319,9 @@ static int mt9m111_probe(struct i2c_client *client)
>  				BIT(V4L2_COLORFX_NEGATIVE) |
>  				BIT(V4L2_COLORFX_SOLARIZATION)),
>  			V4L2_COLORFX_NONE);
> +	v4l2_ctrl_new_std(&mt9m111->hdl, &mt9m111_ctrl_ops, V4L2_CID_PIXEL_RATE,
> +			  mclk_rate, mclk_rate, 1, mclk_rate);
> +

I don't have a datasheet but it seems a little weird that the mclk
frequency is the same as the pixel clock rate ?

>  	mt9m111->subdev.ctrl_handler = &mt9m111->hdl;
>  	if (mt9m111->hdl.error) {
>  		ret = mt9m111->hdl.error;
> --
> 2.30.2
>