Re: [PATCH v4 9/9] media: rcar-csi2: Negotiate data lanes number

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Hi Jacopo, Sakari,

On 15/06/2020 09:34, Sakari Ailus wrote:
> Hi Jacopo,
> 
> On Thu, Jun 11, 2020 at 06:16:51PM +0200, Jacopo Mondi wrote:
>> Use the newly introduced get_mbus_config() subdevice pad operation to
>> retrieve the remote subdevice MIPI CSI-2 bus configuration and configure
>> the number of active data lanes accordingly.
>>
>> In order to be able to call the remote subdevice operation cache the
>> index of the remote pad connected to the single CSI-2 input port.
>>
>> Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
>> ---
>>  drivers/media/platform/rcar-vin/rcar-csi2.c | 61 ++++++++++++++++++++-
>>  1 file changed, 58 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
>> index 151e6a90c5fb..11769f004fd8 100644
>> --- a/drivers/media/platform/rcar-vin/rcar-csi2.c
>> +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
>> @@ -363,6 +363,7 @@ struct rcar_csi2 {
>>  	struct v4l2_async_notifier notifier;
>>  	struct v4l2_async_subdev asd;
>>  	struct v4l2_subdev *remote;
>> +	unsigned int remote_pad;
>>  
>>  	struct v4l2_mbus_framefmt mf;
>>  
>> @@ -371,6 +372,7 @@ struct rcar_csi2 {
>>  
>>  	unsigned short lanes;
>>  	unsigned char lane_swap[4];
>> +	unsigned short active_lanes;
> 
> Do you need this? I.e. should you not always request this from the
> transmitter device?
> 
>>  };
>>  
>>  static inline struct rcar_csi2 *sd_to_csi2(struct v4l2_subdev *sd)
>> @@ -414,7 +416,7 @@ static int rcsi2_wait_phy_start(struct rcar_csi2 *priv)
>>  
>>  	/* Wait for the clock and data lanes to enter LP-11 state. */
>>  	for (timeout = 0; timeout <= 20; timeout++) {
>> -		const u32 lane_mask = (1 << priv->lanes) - 1;
>> +		const u32 lane_mask = (1 << priv->active_lanes) - 1;
>>  
>>  		if ((rcsi2_read(priv, PHCLM_REG) & PHCLM_STOPSTATECKL)  &&
>>  		    (rcsi2_read(priv, PHDLM_REG) & lane_mask) == lane_mask)
>> @@ -471,11 +473,57 @@ static int rcsi2_calc_mbps(struct rcar_csi2 *priv, unsigned int bpp)
>>  	 * bps = link_freq * 2
>>  	 */
>>  	mbps = v4l2_ctrl_g_ctrl_int64(ctrl) * bpp;
>> -	do_div(mbps, priv->lanes * 1000000);
>> +	do_div(mbps, priv->active_lanes * 1000000);
>>  
>>  	return mbps;
>>  }
>>  
>> +static int rcsi2_config_active_lanes(struct rcar_csi2 *priv)
>> +{
>> +	struct v4l2_mbus_config mbus_config = { 0 };
>> +	unsigned int num_lanes = (-1U);
>> +	int ret;
>> +
>> +	priv->active_lanes = priv->lanes;
>> +	ret = v4l2_subdev_call(priv->remote, pad, get_mbus_config,
>> +			       priv->remote_pad, &mbus_config);
>> +	if (ret == -ENOIOCTLCMD) {
>> +		dev_dbg(priv->dev, "No remote mbus configuration available\n");
>> +		return 0;
>> +	}
>> +
>> +	if (ret) {
>> +		dev_err(priv->dev, "Failed to get remote mbus configuration\n");
>> +		return ret;
>> +	}
>> +
>> +	if (mbus_config.type != V4L2_MBUS_CSI2_DPHY) {
>> +		dev_err(priv->dev, "Unsupported media bus type %u\n",
>> +			mbus_config.type);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (mbus_config.flags & V4L2_MBUS_CSI2_1_LANE)
>> +		num_lanes = 1;
>> +	else if (mbus_config.flags & V4L2_MBUS_CSI2_2_LANE)
>> +		num_lanes = 2;
>> +	else if (mbus_config.flags & V4L2_MBUS_CSI2_3_LANE)
>> +		num_lanes = 3;
>> +	else if (mbus_config.flags & V4L2_MBUS_CSI2_4_LANE)
>> +		num_lanes = 4;
> 
> This is the downside of using flags... Anyway, I guess this is certainly
> fine now.

Given that the mbus_config has a .type, can't we easily extend
  struct v4l2_mbus_config

to contain a type specific union ?

Or is that something to do on top of this series instead?

I mean, it could even go after the flags, and keep the flags as a common
attribute - so that no other changes are needed to other components...

--
Kieran

> 
>> +
>> +	if (num_lanes > priv->lanes) {
>> +		dev_err(priv->dev,
>> +			"Unsupported mbus config: too many data lanes %u\n",
>> +			num_lanes);
>> +		return -EINVAL;
>> +	}
>> +
>> +	priv->active_lanes = num_lanes;
>> +
>> +	return 0;
>> +}
>> +
>>  static int rcsi2_start_receiver(struct rcar_csi2 *priv)
>>  {
>>  	const struct rcar_csi2_format *format;
>> @@ -490,6 +538,11 @@ static int rcsi2_start_receiver(struct rcar_csi2 *priv)
>>  	/* Code is validated in set_fmt. */
>>  	format = rcsi2_code_to_fmt(priv->mf.code);
>>  
>> +	/* Get the remote mbus config to get the number of enabled lanes. */
>> +	ret = rcsi2_config_active_lanes(priv);
>> +	if (ret)
>> +		return ret;
>> +
>>  	/*
>>  	 * Enable all supported CSI-2 channels with virtual channel and
>>  	 * data type matching.
>> @@ -522,7 +575,7 @@ static int rcsi2_start_receiver(struct rcar_csi2 *priv)
>>  	}
>>  
>>  	phycnt = PHYCNT_ENABLECLK;
>> -	phycnt |= (1 << priv->lanes) - 1;
>> +	phycnt |= (1 << priv->active_lanes) - 1;
>>  
>>  	mbps = rcsi2_calc_mbps(priv, format->bpp);
>>  	if (mbps < 0)
>> @@ -748,6 +801,7 @@ static int rcsi2_notify_bound(struct v4l2_async_notifier *notifier,
>>  	}
>>  
>>  	priv->remote = subdev;
>> +	priv->remote_pad = pad;
>>  
>>  	dev_dbg(priv->dev, "Bound %s pad: %d\n", subdev->name, pad);
>>  
>> @@ -793,6 +847,7 @@ static int rcsi2_parse_v4l2(struct rcar_csi2 *priv,
>>  			priv->lanes);
>>  		return -EINVAL;
>>  	}
>> +	priv->active_lanes = priv->lanes;
>>  
>>  	for (i = 0; i < ARRAY_SIZE(priv->lane_swap); i++) {
>>  		priv->lane_swap[i] = i < priv->lanes ?
> 

-- 
Regards
--
Kieran



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