Re: [PATCH] media: ov5640: select the MIPI lane mode from the endpoint lane count

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Jason,

Thanks for the patch.

On Tue, Aug 11, 2026 at 12:40:13PM +0800, Jason Yang via B4 Relay wrote:
> From: Jason Yang <jason98166@gmail.com>
> 
> ov5640_set_stream_mipi() always programs IO_MIPI_CTRL00 with 0x45,
> which selects the two data lane mode: the number of data lanes
> described in the devicetree endpoint only feeds the sensor's clock
> tree computations, so a module wired with one data lane starts
> streaming in two lane mode and the receiver never assembles a
> frame.
> 
> Select the lane mode from the endpoint instead. The one lane
> encoding is [7:5] = 001 per the current sensor manual (version
> 2.33). The 2.03 manual documented 000/001 for one/two lanes;
> OmniVision corrected the table in version 2.1, which is why the
> long-standing comment here found 001 unusable for two lanes and
> validated 010 instead.
> 
> The power-up path also programs a two data lane mode, but that
> value is overwritten when streaming starts, so it is left alone.
> 
> Tested with a single data lane module on an i.MX8MP board
> (imx-mipi-csis receiver), where the unpatched value produces no
> frames at all, and on an RK3588 board.
> 
> Fixes: 19a81c1426c1 ("[media] add Omnivision OV5640 sensor driver")
> Cc: stable+noautosel@kernel.org # no in-tree 1-lane users

I guess there wouldn't be harm from backporting either.

> Signed-off-by: Jason Yang <jason98166@gmail.com>
> Assisted-by: Claude:claude-opus-5
> ---
> The three [7:5] encodings were exercised individually on the
> i.MX8MP board (v7.2-rc4, data-lanes = <1>) by patching the value
> and capturing with v4l2-ctl:
> 
>   001 (this patch): 30/30 frames, zero PHY error events in
>       steady state (3 x 300 frames)
>   000 (2.03 manual / NXP KB): same result
>   010 (unpatched two lane mode): no frames; the receiver logs
>       only start-of-transmission errors and never assembles one
> 
> The RK3588 run used the same module and devicetree (data-lanes =
> <1>) through a Rockchip CSI-2 receiver, streaming to natural EOS
> with a clean kernel log.
> 
> Happy to run additional tests on either platform if that would
> help.
> ---
>  drivers/media/i2c/ov5640.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> index 8deb5f5501fa..ef731709bdc8 100644
> --- a/drivers/media/i2c/ov5640.c
> +++ b/drivers/media/i2c/ov5640.c
> @@ -1826,27 +1826,27 @@ static int ov5640_set_stream_dvp(struct ov5640_dev *sensor, bool on)
>  
>  static int ov5640_set_stream_mipi(struct ov5640_dev *sensor, bool on)
>  {
> +	u8 val;
>  	int ret;
>  
>  	/*
>  	 * Enable/disable the MIPI interface
>  	 *
> -	 * 0x300e = on ? 0x45 : 0x40
> -	 *
> -	 * FIXME: the sensor manual (version 2.03) reports
> -	 * [7:5] = 000  : 1 data lane mode
> -	 * [7:5] = 001  : 2 data lanes mode
> -	 * But this settings do not work, while the following ones
> -	 * have been validated for 2 data lanes mode.
> -	 *
> +	 * [7:5] = 001	: 1 data lane mode
>  	 * [7:5] = 010	: 2 data lanes mode
> +	 *		  Encodings per version 2.33 of the sensor manual.
>  	 * [4] = 0	: Power up MIPI HS Tx
>  	 * [3] = 0	: Power up MIPI LS Rx
>  	 * [2] = 1/0	: MIPI interface enable/disable
>  	 * [1:0] = 01/00: FIXME: 'debug'
>  	 */
> -	ret = ov5640_write_reg(sensor, OV5640_REG_IO_MIPI_CTRL00,
> -			       on ? 0x45 : 0x40);
> +	if (on)
> +		val = sensor->ep.bus.mipi_csi2.num_data_lanes == 1 ?
> +		      0x25 : 0x45;

How about:

	ret = ov5640_write_reg(sensor, OV5640_REG_IO_MIPI_CTRL00,
			       on ? 0x5 | ep.bus.mipi_csi2.num_data_lanes << 5 :
			       0x40);

> +	else
> +		val = 0x40;
> +
> +	ret = ov5640_write_reg(sensor, OV5640_REG_IO_MIPI_CTRL00, val);
>  	if (ret)
>  		return ret;
>  
> @@ -2535,7 +2535,7 @@ static int ov5640_set_power_mipi(struct ov5640_dev *sensor, bool on)
>  	 * Power up MIPI HS Tx and LS Rx; 2 data lanes mode
>  	 *
>  	 * 0x300e = 0x40
> -	 * [7:5] = 010	: 2 data lanes mode (see FIXME note in
> +	 * [7:5] = 010	: 2 data lanes mode (see the note in
>  	 *		  "ov5640_set_stream_mipi()")

Do we need quotes?

>  	 * [4] = 0	: Power up MIPI HS Tx
>  	 * [3] = 0	: Power up MIPI LS Rx
> 

-- 
Kind regards,

Sakari Ailus