[13/19] media: max9286: Implement support for LINK_FREQ

The max9286 now supports multiple streams. For this reason, reporting
the data bitrate through the PIXEL_RATE control is not meaningful
anymore (or better, is less meaningful that what it already was).

In order to support multiplexed receivers, which want to be informed
about the CSI-2 link frequency, implement support for the
V4L2_CID_LINK_FREQ control.

Record in the driver a set of pre-computed link frequencies in order to
support the two currently supported GMSL camera modules (rdacm20 and
rdacm21) and all the supported number of active channels and CSI-2 data
lanes.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
 drivers/media/i2c/max9286.c | 143 ++++++++++++++++++++++++++++++++++--
 1 file changed, 136 insertions(+), 7 deletions(-)

Hi Jacopo,

Thank you for the patch.

On Tue, Apr 30, 2024 at 12:39:49PM +0200, Jacopo Mondi wrote:
> The max9286 now supports multiple streams. For this reason, reporting
> the data bitrate through the PIXEL_RATE control is not meaningful
> anymore (or better, is less meaningful that what it already was).
> 
> In order to support multiplexed receivers, which want to be informed
> about the CSI-2 link frequency, implement support for the
> V4L2_CID_LINK_FREQ control.

I think
https://lore.kernel.org/linux-media/20240429190852.1008003-3-sakari.ailus@linux.intel.com
may be more suitable for this use case.

> 
> Record in the driver a set of pre-computed link frequencies in order to
> support the two currently supported GMSL camera modules (rdacm20 and

s/camera modules/cameras/

> rdacm21) and all the supported number of active channels and CSI-2 data
> lanes.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
> ---
>  drivers/media/i2c/max9286.c | 143 ++++++++++++++++++++++++++++++++++--
>  1 file changed, 136 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index 4b4f4c03c10a..0e08a1041eed 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -148,6 +148,12 @@ struct max9286_format_info {
>  	u32 code;
>  	/* The gmsl data format configuration. */
>  	u8 gmsl_dt;
> +	/*
> +	 * gmsl_bpp is the pixel format bit-width per word as reported in
> +	 * table 20. and it is used to calculate the GMSL bandwidth and CSI-2

Table 20 of what ?

> +	 * link speed.
> +	 */
> +	u8 gmsl_bpp;
>  	/* The format bpp, used for stride calculation. */
>  	u8 bpp;
>  	/* The Data Type identifier as defined by the MIPI CSI-2 standard. */
> @@ -201,6 +207,7 @@ struct max9286_priv {
>  
>  	struct v4l2_ctrl_handler ctrls;
>  	struct v4l2_ctrl *pixelrate_ctrl;
> +	struct v4l2_ctrl *link_freq;
>  	unsigned int pixelrate;
>  
>  	unsigned int nsources;
> @@ -242,41 +249,49 @@ static const struct max9286_format_info max9286_formats[] = {
>  	{
>  		.code = MEDIA_BUS_FMT_UYVY8_1X16,
>  		.gmsl_dt = MAX9286_DATATYPE_YUV422_8BIT,
> +		.gmsl_bpp = 8,
>  		.bpp = 16,
>  		.mipi_dt = MIPI_CSI2_DT_YUV422_8B,
>  	}, {
>  		.code = MEDIA_BUS_FMT_VYUY8_1X16,
>  		.gmsl_dt = MAX9286_DATATYPE_YUV422_8BIT,
> +		.gmsl_bpp = 8,
>  		.bpp = 16,
>  		.mipi_dt = MIPI_CSI2_DT_YUV422_8B,
>  	}, {
>  		.code = MEDIA_BUS_FMT_YUYV8_1X16,
>  		.gmsl_dt = MAX9286_DATATYPE_YUV422_8BIT,
> +		.gmsl_bpp = 8,
>  		.bpp = 16,
>  		.mipi_dt = MIPI_CSI2_DT_YUV422_8B,
>  	}, {
>  		.code = MEDIA_BUS_FMT_YVYU8_1X16,
>  		.gmsl_dt = MAX9286_DATATYPE_YUV422_8BIT,
> +		.gmsl_bpp = 8,
>  		.bpp = 16,
>  		.mipi_dt = MIPI_CSI2_DT_YUV422_8B,
>  	}, {
>  		.code = MEDIA_BUS_FMT_SBGGR12_1X12,
>  		.gmsl_dt = MAX9286_DATATYPE_RAW12,
> +		.gmsl_bpp = 12,
>  		.bpp = 12,
>  		.mipi_dt = MIPI_CSI2_DT_RAW12,
>  	}, {
>  		.code = MEDIA_BUS_FMT_SGBRG12_1X12,
>  		.gmsl_dt = MAX9286_DATATYPE_RAW12,
> +		.gmsl_bpp = 12,
>  		.bpp = 12,
>  		.mipi_dt = MIPI_CSI2_DT_RAW12,
>  	}, {
>  		.code = MEDIA_BUS_FMT_SGRBG12_1X12,
>  		.gmsl_dt = MAX9286_DATATYPE_RAW12,
> +		.gmsl_bpp = 12,
>  		.bpp = 12,
>  		.mipi_dt = MIPI_CSI2_DT_RAW12,
>  	}, {
>  		.code = MEDIA_BUS_FMT_SRGGB12_1X12,
>  		.gmsl_dt = MAX9286_DATATYPE_RAW12,
> +		.gmsl_bpp = 12,
>  		.bpp = 12,
>  		.mipi_dt = MIPI_CSI2_DT_RAW12,
>  	},
> @@ -293,6 +308,60 @@ static const struct max9286_i2c_speed max9286_i2c_speeds[] = {
>  	{ .rate = 837000, .mstbt = MAX9286_I2CMSTBT_837KBPS },
>  };
>  
> +/*
> + * According to the chip manual the CSI-2 link frequency is calculated as:
> + *
> + *     f-CSI2 = pclk * ((width * channels) / lanes)
> + *
> + * Where:
> + *     pclk = serializer input word rate
> + *     width = pixel format bits per word (gmsl_bpp in max9286_format_info)
> + *     channels = number of enabled links
> + *     lanes = number of CSI-2 data lanes
> + *
> + * The following link frequencies have been computed by combining the following
> + * parameters:
> + *
> + * pixel_rates[] = { 44000000, 55000000 }; for RDACM20 and RDACM21
> + * bpps[] = { 8, 12 }; for the formats supported by the max9286 driver
> + * channels[] = { 1, 2, 3, 4 };
> + * lanes[] = { 1, 2, 3, 4 };
> + *
> + * and by filtering out all results that would lead to an invalid
> + * link_frequency, as the MAX9286 has a CSI-2 bandwidth limit of 1200Mbps per
> + * lane (600MHz clock frequency).
> + *
> + * If a new serializer with a different pixel rate, or a new image format with
> + * a different bpp is supported, the below table needs to be updated.
> + */
> +static const s64 max9286_link_freqs[] = {
> +	88000000,
> +	110000000,
> +	132000000,
> +	165000000,
> +	176000000,
> +	220000000,
> +	264000000,
> +	275000000,
> +	330000000,
> +	352000000,
> +	396000000,
> +	440000000,
> +	495000000,
> +	528000000,
> +	550000000,
> +};
> +
> +static int max9286_get_link_freq_index(s64 link_freq)
> +{
> +	for (unsigned int i = 0; i < ARRAY_SIZE(max9286_link_freqs); ++i) {
> +		if (max9286_link_freqs[i] == link_freq)
> +			return i;
> +	}
> +
> +	return -EINVAL;
> +}
> +
>  /* -----------------------------------------------------------------------------
>   * I2C IO
>   */
> @@ -636,10 +705,18 @@ static void max9286_set_fsync_period(struct max9286_priv *priv,
>   * V4L2 Subdev
>   */
>  
> -static int max9286_set_pixelrate(struct max9286_priv *priv)
> +static int max9286_set_pixelrate(struct max9286_priv *priv,
> +				 struct v4l2_subdev_state *state,
> +				 unsigned int link_index)
>  {
> +	const struct max9286_format_info *info;
>  	struct max9286_source *source = NULL;
> +	struct v4l2_mbus_framefmt *fmt;
> +	unsigned int num_sources = 0;
> +	int link_freq_index;
>  	u64 pixelrate = 0;
> +	s64 link_freq;
> +	int ret;
>  
>  	for_each_source(priv, source) {
>  		struct v4l2_ctrl *ctrl;
> @@ -662,6 +739,8 @@ static int max9286_set_pixelrate(struct max9286_priv *priv)
>  				"Unable to calculate pixel rate\n");
>  			return -EINVAL;
>  		}
> +
> +		num_sources++;
>  	}
>  
>  	if (!pixelrate) {
> @@ -670,14 +749,33 @@ static int max9286_set_pixelrate(struct max9286_priv *priv)
>  		return -EINVAL;
>  	}
>  
> -	priv->pixelrate = pixelrate;
> +	fmt = v4l2_subdev_state_get_format(state, link_index);
> +	info = max9286_get_format_info(fmt->code);
> +	if (WARN_ON(!info))
> +		return -EINVAL;
> +
> +	/*
> +	 * Compute the link frequency and find the right index to update
> +	 * the menu control with.
> +	 */
> +	link_freq = pixelrate * ((info->gmsl_bpp * num_sources) /
> +		    priv->csi2_data_lanes);
> +
> +	link_freq_index = max9286_get_link_freq_index(link_freq);
> +	if (WARN_ON(link_freq_index < 0))
> +		return -EINVAL;
>  
>  	/*
>  	 * The CSI-2 transmitter pixel rate is the single source rate multiplied
>  	 * by the number of available sources.
>  	 */
> -	return v4l2_ctrl_s_ctrl_int64(priv->pixelrate_ctrl,
> -				      pixelrate * priv->nsources);
> +	ret = __v4l2_ctrl_s_ctrl_int64(priv->pixelrate_ctrl,
> +				       pixelrate * priv->nsources);
> +	if (ret)
> +		return -EINVAL;
> +	priv->pixelrate = pixelrate;
> +
> +	return __v4l2_ctrl_s_ctrl(priv->link_freq, link_freq_index);
>  }
>  
>  static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
> @@ -687,6 +785,7 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
>  	struct max9286_priv *priv = sd_to_max9286(notifier->sd);
>  	struct max9286_source *source = to_max9286_asd(asd)->source;
>  	unsigned int index = to_index(priv, source);
> +	struct v4l2_subdev_state *state;
>  	unsigned int src_pad;
>  	int ret;
>  
> @@ -739,7 +838,11 @@ static int max9286_notify_bound(struct v4l2_async_notifier *notifier,
>  	max9286_check_config_link(priv, priv->source_mask);
>  	max9286_configure_i2c(priv, false);
>  
> -	return max9286_set_pixelrate(priv);
> +	state = v4l2_subdev_lock_and_get_active_state(notifier->sd);
> +	ret = max9286_set_pixelrate(priv, state, index);
> +	v4l2_subdev_unlock_state(state);
> +
> +	return ret;
>  }
>  
>  static void max9286_notify_unbind(struct v4l2_async_notifier *notifier,
> @@ -926,7 +1029,9 @@ static int max9286_set_fmt(struct v4l2_subdev *sd,
>  			   struct v4l2_subdev_state *state,
>  			   struct v4l2_subdev_format *format)
>  {
> +	struct max9286_priv *priv = sd_to_max9286(sd);
>  	const struct max9286_format_info *info;
> +	int ret;
>  
>  	/*
>  	 * Disable setting format on the source pad: format is propagated
> @@ -949,7 +1054,22 @@ static int max9286_set_fmt(struct v4l2_subdev *sd,
>  	*v4l2_subdev_state_get_opposite_stream_format(state, format->pad, 0) =
>  		format->format;
>  
> -	return 0;
> +	/*
> +	 * Update the pixel rate and link_rate controls. We cannot do that in
> +	 * s_stream() as the receiver is likely fetching the frame_desc and
> +	 * reading the link_rate control before calling this driver's s_stream.
> +	 *
> +	 * Update the controls here.
> +	 *
> +	 * TODO: Once the routing table will be made writable and links
> +	 * can be enabled/disabled, the controls need to be updated there too.
> +	 */
> +	ret = max9286_set_pixelrate(priv, state, format->pad);
> +	if (ret)
> +		dev_err(&priv->client->dev,
> +			"Unsupported format/lanes/channel combination: clock rate too high");
> +
> +	return ret;
>  }
>  
>  static int max9286_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
> @@ -1068,6 +1188,7 @@ static int max9286_s_ctrl(struct v4l2_ctrl *ctrl)
>  {
>  	switch (ctrl->id) {
>  	case V4L2_CID_PIXEL_RATE:
> +	case V4L2_CID_LINK_FREQ:
>  		return 0;
>  	default:
>  		return -EINVAL;
> @@ -1097,12 +1218,20 @@ static int max9286_v4l2_register(struct max9286_priv *priv)
>  	priv->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE |
>  			  V4L2_SUBDEV_FL_STREAMS;
>  
> -	v4l2_ctrl_handler_init(&priv->ctrls, 1);
> +	v4l2_ctrl_handler_init(&priv->ctrls, 2);
>  	priv->pixelrate_ctrl = v4l2_ctrl_new_std(&priv->ctrls,
>  						 &max9286_ctrl_ops,
>  						 V4L2_CID_PIXEL_RATE,
>  						 1, INT_MAX, 1, 50000000);
>  
> +	priv->link_freq =
> +		v4l2_ctrl_new_int_menu(&priv->ctrls, &max9286_ctrl_ops,
> +				       V4L2_CID_LINK_FREQ,
> +				       ARRAY_SIZE(max9286_link_freqs) - 1, 0,
> +				       max9286_link_freqs);
> +	if (priv->link_freq)
> +		priv->link_freq->flags |= V4L2_CTRL_FLAG_READ_ONLY;
> +
>  	priv->sd.ctrl_handler = &priv->ctrls;
>  	ret = priv->ctrls.error;
>  	if (ret)