Message-ID: <85243712-e09f-43c3-bdcc-4a7e7be4dc52@ti.com>
Date: Wed, 28 May 2025 11:55:18 +0530
From: Yemike Abhilash Chandra <y-abhilashchandra@...com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
CC: <hverkuil@...all.nl>, <sakari.ailus@...ux.intel.com>,
        <laurent.pinchart@...asonboard.com>, <vaishnav.a@...com>,
        <u-kumar1@...com>, <jai.luthra@...ux.dev>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <mchehab@...nel.org>,
        <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>
Subject: Re: [PATCH 2/2] media: i2c: ds90ub960: Add support for DS90UB954-Q1

Hi Tomi,

Thanks for the review.

On 27/05/25 11:10, Tomi Valkeinen wrote:
> Hi,
> 
> On 23/05/2025 11:36, Yemike Abhilash Chandra wrote:
>> DS90UB954-Q1 is an FPDLink-III deserializer that is mostly register
>> compatible with DS90UB960-Q1. The main difference is that it supports
>> half of the RX and TX ports, i.e. 2x FPDLink RX ports and 1x CSI TX
>> port.
>>
>> Some other registers are marked as reserved in the datasheet as well,
>> notably around CSI-TX frame and line-count monitoring and some other
> 
> Hmm what does that mean? That in log_status we show random data (or
> maybe always 0) for these?
> 

It seems like it is showing 0's for these. I streamed around 100 frames.
But the frame counter and line counter returned is 0. Please find the
logs at [1].

>> status registers. The datasheet also does not mention anything about
>> setting strobe position, and fails to lock the RX ports if we forcefully
>> set it, so disable it through the hw_data.
> 
> This app-note has some details:
> 
> https://www.ti.com/lit/an/snla301/snla301.pdf
> 
>> Link: https://www.ti.com/lit/gpn/ds90ub954-q1
>> Signed-off-by: Yemike Abhilash Chandra <y-abhilashchandra@...com>
>> ---
>>   drivers/media/i2c/Kconfig     |  2 +-
>>   drivers/media/i2c/ds90ub960.c | 46 +++++++++++++++++++++++++++++++++++
>>   2 files changed, 47 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
>> index e68202954a8f..6e265e1cec20 100644
>> --- a/drivers/media/i2c/Kconfig
>> +++ b/drivers/media/i2c/Kconfig
>> @@ -1662,7 +1662,7 @@ config VIDEO_DS90UB960
>>   	select V4L2_FWNODE
>>   	select VIDEO_V4L2_SUBDEV_API
>>   	help
>> -	  Device driver for the Texas Instruments DS90UB960
>> +	  Device driver for the Texas Instruments DS90UB954/DS90UB960
>>   	  FPD-Link III Deserializer and DS90UB9702 FPD-Link IV Deserializer.
>>   
>>   config VIDEO_MAX96714
>> diff --git a/drivers/media/i2c/ds90ub960.c b/drivers/media/i2c/ds90ub960.c
>> index ed2cf9d247d1..38e4f006d098 100644
>> --- a/drivers/media/i2c/ds90ub960.c
>> +++ b/drivers/media/i2c/ds90ub960.c
>> @@ -460,6 +460,7 @@ struct ub960_hw_data {
>>   	u8 num_txports;
>>   	bool is_ub9702;
>>   	bool is_fpdlink4;
>> +	bool is_ub954;
> 
> No, let's not add any more of these. We should have enums for the device
> model and the "family" (ub954/ub960 are clearly of the same family,
> whereas ub9702 is of a newer one).
> 

Got it. I will add enums in the next revision.

>>   };
>>   
>>   enum ub960_rxport_mode {
>> @@ -982,6 +983,10 @@ static int ub960_txport_select(struct ub960_data *priv, u8 nport)
>>   
>>   	lockdep_assert_held(&priv->reg_lock);
>>   
>> +	/* TX port registers are shared for UB954*/
> 
> Space missing at the end. What does the comment mean? "registers are
> shared"?
> 

Apologies for the inaccurate comment description, My intention to
comment that the tx_port_select function does not make sense for
UB954, since we have only 1 CSI TX. May be I can have something
like below.

/** UB954 has only 1 CSI TX. Hence, no need to select **/

> I think it's good to have this after the lockdep assert. The lock rules
> are in place, even if on ub954 we don't do anything here.
> 
>> +	if (priv->hw_data->is_ub954)
>> +		return 0;
>> +
>>   	if (priv->reg_current.txport == nport)
>>   		return 0;
>>   
>> @@ -1415,6 +1420,13 @@ static int ub960_parse_dt_txport(struct ub960_data *priv,
>>   		goto err_free_vep;
>>   	}
>>   
>> +	/* UB954 does not support 1.2 Gbps */
>> +	if (priv->tx_data_rate == MHZ(1200) && priv->hw_data->is_ub954) {
> 
> Test for ub954 first, 1200 MHz second. It's more logical for the reader
> that way.
> 

Noted, will do that in the next revision.

>> +		dev_err(dev, "tx%u: invalid 'link-frequencies' value\n", nport);
>> +		ret = -EINVAL;
>> +		goto err_free_vep;
>> +	}
>> +
>>   	v4l2_fwnode_endpoint_free(&vep);
>>   
>>   	priv->txports[nport] = txport;
>> @@ -1572,6 +1584,10 @@ static int ub960_rxport_set_strobe_pos(struct ub960_data *priv,
>>   	u8 clk_delay, data_delay;
>>   	int ret = 0;
>>   
>> +	/* FIXME: After writing to this area the UB954 chip no longer responds */
>> +	if (priv->hw_data->is_ub954)
>> +		return 0;
>> +
> 
> Check the app note. It would be nice to have this working, as, afaik,
> the HW functionality should be the same on ub954 and ub960.
> 

I tried referring the app note and changed the strobe position values
accordingly, but it did not help.

Since the app note also specifies the below at Table 2 Strobe Adaption Modes

"
AEQ Adaption Mode--> Strobe position is selected as part of AEQ. This is 
the default mode.

Manual Adaption Mode --> The strobe position is selected manually and 
will remain at
the specified position until a new one is chosen. This mode is 
recommended as an
evaluation and debugging mode "

Since, under the default settings, the strobe position is selected as 
part of the AEQ process.
Can we limit the ub960_rxport_set_strobe_pos function to only UB960 and 
UB9702.

>>   	clk_delay = UB960_IR_RX_ANA_STROBE_SET_CLK_NO_EXTRA_DELAY;
>>   	data_delay = UB960_IR_RX_ANA_STROBE_SET_DATA_NO_EXTRA_DELAY;
>>   
>> @@ -5021,6 +5037,27 @@ static int ub960_enable_core_hw(struct ub960_data *priv)
>>   	if (priv->hw_data->is_ub9702)
>>   		ret = ub960_read(priv, UB9702_SR_REFCLK_FREQ, &refclk_freq,
>>   				 NULL);
>> +	else if (priv->hw_data->is_ub954) {
>> +		/* From DS90UB954-Q1 datasheet:
>> +		 * "REFCLK_FREQ measurement is not synchronized. Value in this
>> +		 * register should read twice and only considered valid if
>> +		 * REFCLK_FREQ is unchanged between reads."
>> +		 */
>> +		unsigned long timeout = jiffies + msecs_to_jiffies(100);
>> +
>> +		do {
>> +			u8 refclk_new;
>> +
>> +			ret = ub960_read(priv, UB960_XR_REFCLK_FREQ, &refclk_new,
>> +					 NULL);
>> +			if (ret)
>> +				goto err_pd_gpio;
>> +
>> +			if (refclk_new == refclk_freq)
>> +				break;
>> +			refclk_freq = refclk_new;
>> +		} while (time_before(jiffies, timeout));
>> +	}
> 
> This feels a bit too much for a not-that-important debug print... As the
> tests show that a single read is (practically always?) enough, I think
> we can just use the same code as for ub960. Maybe add a comment about
> it, though.
> 

okay, I will use the same code that is being used for UB960 and will add 
a comment
about that.

Thanks and Regards,
Abhilash Chandra

[1]: 
https://gist.github.com/Yemike-Abhilash-Chandra/c6b3da2a10586567a3a4179a2b20d21b

>   Tomi
> 
>>   	else
>>   		ret = ub960_read(priv, UB960_XR_REFCLK_FREQ, &refclk_freq,
>>   				 NULL);
>> @@ -5177,6 +5214,13 @@ static void ub960_remove(struct i2c_client *client)
>>   	mutex_destroy(&priv->reg_lock);
>>   }
>>   
>> +static const struct ub960_hw_data ds90ub954_hw = {
>> +	.model = "ub954",
>> +	.num_rxports = 2,
>> +	.num_txports = 1,
>> +	.is_ub954 = true,
>> +};
>> +
>>   static const struct ub960_hw_data ds90ub960_hw = {
>>   	.model = "ub960",
>>   	.num_rxports = 4,
>> @@ -5192,6 +5236,7 @@ static const struct ub960_hw_data ds90ub9702_hw = {
>>   };
>>   
>>   static const struct i2c_device_id ub960_id[] = {
>> +	{ "ds90ub954-q1", (kernel_ulong_t)&ds90ub954_hw },
>>   	{ "ds90ub960-q1", (kernel_ulong_t)&ds90ub960_hw },
>>   	{ "ds90ub9702-q1", (kernel_ulong_t)&ds90ub9702_hw },
>>   	{}
>> @@ -5199,6 +5244,7 @@ static const struct i2c_device_id ub960_id[] = {
>>   MODULE_DEVICE_TABLE(i2c, ub960_id);
>>   
>>   static const struct of_device_id ub960_dt_ids[] = {
>> +	{ .compatible = "ti,ds90ub954-q1", .data = &ds90ub954_hw },
>>   	{ .compatible = "ti,ds90ub960-q1", .data = &ds90ub960_hw },
>>   	{ .compatible = "ti,ds90ub9702-q1", .data = &ds90ub9702_hw },
>>   	{}
> 

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