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

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Hi Jacopo,

On 15/06/2020 09:43, Jacopo Mondi wrote:
> Hi Sakari,
> 
> On Mon, Jun 15, 2020 at 11:34:06AM +0300, 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?
> 
> It's actually the other way around. The receiver queries the
> transmitter to know how many data lanes it intends to use and adjusts
> its configuration to accommodate it.
> 
>>
>>>  };
>>>
>>>  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.
>>
> 
> Let's change this on top, if we like to (and I would like to :)

That answers my question then ;-)

--
Kieran


> 
> Thanks
>   j
> 
>>> +
>>> +	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 ?
>>
>> --
>> Kind regards,
>>
>> Sakari Ailus

-- 
Regards
--
Kieran



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