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Message-ID: <CAPY8ntCiaTMdM_FRo3k9mYrzVnAuJYXrZU70Hf5=fLxButCOmg@mail.gmail.com>
Date: Tue, 4 Mar 2025 17:30:13 +0000
From: Dave Stevenson <dave.stevenson@...pberrypi.com>
To: Richard Leitner <richard.leitner@...ux.dev>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>, Laurent Pinchart <laurent.pinchart@...asonboard.com>,
linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] media: i2c: ov9282: add strobe_timeout v4l2 control
On Tue, 4 Mar 2025 at 10:28, Dave Stevenson
<dave.stevenson@...pberrypi.com> wrote:
>
> Hi Richard
>
> On Mon, 3 Mar 2025 at 22:59, Richard Leitner <richard.leitner@...ux.dev> wrote:
> >
> > Add V4L2_CID_FLASH_TIMEOUT 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 framerate.
> > This must be changed to a dynamic range as soon as this driver
> > implements the set_frame_interval() pad operation.
Rereading the patch as I'm looking at the whole series.
set_frame_interval() will never be implemented as it is the wrong API
for raw sensors.
See https://www.kernel.org/doc/html/latest/userspace-api/media/drivers/camera-sensor.html#raw-camera-sensors
This driver already implements PIXEL_RATE, HBLANK, and VBLANK for
frame interval configuration.
> >
> > 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 | 31 +++++++++++++++++++++++++++++++
> > 1 file changed, 31 insertions(+)
> >
> > diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> > index c98ba466e9aea29baff0b13578d760bf69c958c5..f7dfe8987e524b73af7e16e12567e96627b4f89a 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
> >
> > @@ -193,6 +197,7 @@ struct ov9282_mode {
> > * @again_ctrl: Pointer to analog gain control
> > * @pixel_rate: Pointer to pixel rate control
> > * @flash_led_mode: Pointer to flash led mode control
> > + * @flash_timeout: Pointer to flash timeout control
> > * @vblank: Vertical blanking in lines
> > * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
> > * @cur_mode: Pointer to current selected sensor mode
> > @@ -216,6 +221,7 @@ struct ov9282 {
> > };
> > struct v4l2_ctrl *pixel_rate;
> > struct v4l2_ctrl *flash_led_mode;
> > + struct v4l2_ctrl *flash_timeout;
>
> You only access this in ov9282_set_ctrl where you already have the
> struct v4l2_ctrl, so there is no need to store this in the main device
> state.
>
> Dave
>
> > u32 vblank;
> > bool noncontinuous_clock;
> > const struct ov9282_mode *cur_mode;
> > @@ -689,6 +695,24 @@ static int ov9282_set_ctrl_flash_led_mode(struct ov9282 *ov9282, int mode)
> > current_val);
> > }
> >
> > +static int ov9282_set_ctrl_flash_timeout(struct ov9282 *ov9282, int value)
> > +{
> > + /* Calculate "strobe_frame_span" increments from a given value (µs).
> > + * 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);
> > +}
> > +
> > /**
> > * ov9282_set_ctrl() - Set subdevice control
> > * @ctrl: pointer to v4l2_ctrl structure
> > @@ -758,6 +782,9 @@ 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_TIMEOUT:
> > + ret = ov9282_set_ctrl_flash_timeout(ov9282, ctrl->val);
> > + break;
> > default:
> > dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
> > ret = -EINVAL;
> > @@ -1420,6 +1447,10 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
> > (1 << V4L2_FLASH_LED_MODE_TORCH),
> > V4L2_FLASH_LED_MODE_NONE);
> >
> > + ov9282->flash_timeout = v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
> > + V4L2_CID_FLASH_TIMEOUT,
> > + 0, 13900, 1, 8);
> > +
> > ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
> > if (!ret) {
> > /* Failure sets ctrl_hdlr->error, which we check afterwards anyway */
> >
> > --
> > 2.47.2
> >
> >
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