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Message-ID: <aBHe-55_U3bYTXyG@kekkonen.localdomain>
Date: Wed, 30 Apr 2025 08:27:39 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Richard Leitner <richard.leitner@...ux.dev>
Cc: Dave Stevenson <dave.stevenson@...pberrypi.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [PATCH v3 8/9] media: i2c: ov9282: add strobe_duration v4l2
control
Hi Richard,
On Tue, Apr 29, 2025 at 02:59:13PM +0200, Richard Leitner wrote:
> Add V4L2_CID_FLASH_DURATION support using the "strobe_frame_span"
> feature of the sensor. This is implemented by transforming the given µs
> value by an interpolated formula to a "span step width" value and
> writing it to register PWM_CTRL_25, PWM_CTRL_26, PWM_CTRL_27,
> PWM_CTRL_28 (0x3925, 0x3926, 0x3927, 0x3928).
>
> The maximum control value is set to the period of the current default
> framerate.
>
> All register values are based on the OV9281 datasheet v1.53 (jan 2019)
> and tested using an ov9281 VisionComponents module.
>
> Signed-off-by: Richard Leitner <richard.leitner@...ux.dev>
> ---
> drivers/media/i2c/ov9282.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> index 35edbe1e0efb61a0e03da0ed817c4c4ec0ae9c35..5ddbfc51586111fbd2e17b739fb3d28bfb0aee1e 100644
> --- a/drivers/media/i2c/ov9282.c
> +++ b/drivers/media/i2c/ov9282.c
> @@ -97,6 +97,10 @@
> #define OV9282_REG_MIPI_CTRL00 0x4800
> #define OV9282_GATED_CLOCK BIT(5)
>
> +/* Flash/Strobe control registers */
> +#define OV9282_REG_FLASH_DURATION 0x3925
> +#define OV9282_FLASH_DURATION_DEFAULT 0x0000001A
> +
> /* Input clock rate */
> #define OV9282_INCLK_RATE 24000000
>
> @@ -687,6 +691,24 @@ static int ov9282_set_ctrl_flash_led_mode(struct ov9282 *ov9282, int mode)
> current_val);
> }
>
> +static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, int value)
> +{
> + /* Calculate "strobe_frame_span" increments from a given value (µs).
/*
* Multi-line
* comment.
*/
> + * This is quite tricky as "The step width of shift and span is
> + * programmable under system clock domain.", but it's not documented
> + * how to program this step width (at least in the datasheet available
> + * to the author at time of writing).
> + * The formula below is interpolated from different modes/framerates
> + * and should work quite well for most settings.
> + */
> + u32 val = value * 192 / (ov9282->cur_mode->width + ov9282->hblank_ctrl->val);
> +
> + ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION, 1, (val >> 24) & 0xff);
> + ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 1, 1, (val >> 16) & 0xff);
> + ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 2, 1, (val >> 8) & 0xff);
> + return ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 3, 1, val & 0xff);
The granularity of the hardware supported values is lower than that of the
control. Could you add try_ctrl op to provide the actual value back to the
user space?
> +}
> +
> /**
> * ov9282_set_ctrl() - Set subdevice control
> * @ctrl: pointer to v4l2_ctrl structure
> @@ -756,6 +778,9 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
> case V4L2_CID_FLASH_LED_MODE:
> ret = ov9282_set_ctrl_flash_led_mode(ov9282, ctrl->val);
> break;
> + case V4L2_CID_FLASH_DURATION:
> + ret = ov9282_set_ctrl_flash_duration(ov9282, ctrl->val);
> + break;
> default:
> dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
> ret = -EINVAL;
> @@ -1418,6 +1443,9 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
> (1 << V4L2_FLASH_LED_MODE_TORCH),
> V4L2_FLASH_LED_MODE_NONE);
>
> + v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
Should the number of controls in the handler be updated?
> + 0, 13900, 1, 8);
> +
> ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
> if (!ret) {
> /* Failure sets ctrl_hdlr->error, which we check afterwards anyway */
>
--
Regards,
Sakari Ailus
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