diff mbox series

[v14,18/18] media: i2c: ds90ub953: Support non-sync mode

Message ID	20230616135922.442979-19-tomi.valkeinen@ideasonboard.com
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; From: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> To: linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, Luca Ceresoli <luca.ceresoli@bootlin.com>, Andy Shevchenko <andriy.shevchenko@intel.com>, Matti Vaittinen <Matti.Vaittinen@fi.rohmeurope.com>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>, Sakari Ailus <sakari.ailus@linux.intel.com> Cc: Wolfram Sang <wsa@kernel.org>, Rob Herring <robh+dt@kernel.org>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Mauro Carvalho Chehab <mchehab@kernel.org>, Peter Rosin <peda@axentia.se>, Liam Girdwood <lgirdwood@gmail.com>, Mark Brown <broonie@kernel.org>, Michael Tretter <m.tretter@pengutronix.de>, Hans Verkuil <hverkuil@xs4all.nl>, Mike Pagano <mpagano@gentoo.org>, =?utf-8?q?Krzysztof_Ha=C5=82asa?= <khalasa@piap.pl>, Marek Vasut <marex@denx.de>, Satish Nagireddy <satish.nagireddy@getcruise.com>, Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> Subject: [PATCH v14 18/18] media: i2c: ds90ub953: Support non-sync mode Date: Fri, 16 Jun 2023 16:59:22 +0300 Message-Id: <20230616135922.442979-19-tomi.valkeinen@ideasonboard.com> In-Reply-To: <20230616135922.442979-1-tomi.valkeinen@ideasonboard.com> References: <20230616135922.442979-1-tomi.valkeinen@ideasonboard.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	i2c-atr and FPDLink \| [v14,00/18] i2c-atr and FPDLink [v14,01/18] dt-bindings: i2c: Add I2C Address Translator (ATR) [v14,02/18] i2c: add I2C Address Translator (ATR) support [v14,03/18] dt-bindings: media: add TI DS90UB913 FPD-Link III Serializer [v14,04/18] dt-bindings: media: add TI DS90UB953 FPD-Link III Serializer [v14,05/18] dt-bindings: media: add TI DS90UB960 FPD-Link III Deserializer [v14,06/18] media: i2c: add DS90UB960 driver [v14,07/18] media: i2c: add DS90UB913 driver [v14,08/18] media: i2c: add DS90UB953 driver [v14,09/18] media: i2c: ds90ub960: Fix use of UB960_SR_FWD_CTL1 [v14,10/18] media: i2c: ds90ub9xx: Add COMMON_CLK kconfig dependency [v14,11/18] media: i2c: ds90ub9xx: Select GPIOLIB rather than OF_GPIO [v14,12/18] media: i2c: ds90ub960: Configure CSI-2 continuous clock [v14,13/18] media: i2c: ds90ub953: Use v4l2_fwnode_endpoint_parse() [v14,14/18] media: i2c: ds90ub913: Use v4l2_fwnode_endpoint_parse() [v14,15/18] media: i2c: ds90ub953: Handle V4L2_MBUS_CSI2_NONCONTINUOUS_CLOCK [v14,16/18] media: i2c: ds90ub960: Allow FPD-Link async mode [v14,17/18] media: i2c: ds90ub953: Restructure clkout management [v14,18/18] media: i2c: ds90ub953: Support non-sync mode

Commit Message

Tomi Valkeinen June 16, 2023, 1:59 p.m. UTC

  Add support for FPD-Link non-sync mode with external clock. The only
thing that needs to be added is the calculation for the clkout.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 drivers/media/i2c/ds90ub953.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

Comments

Andy Shevchenko June 16, 2023, 2:47 p.m. UTC | #1

On Fri, Jun 16, 2023 at 04:59:22PM +0300, Tomi Valkeinen wrote:
> Add support for FPD-Link non-sync mode with external clock. The only
> thing that needs to be added is the calculation for the clkout.

...

> +	switch (priv->mode) {
> +	case UB953_MODE_SYNC:
> +		if (priv->hw_data->is_ub971)
> +			return priv->plat_data->bc_rate * 160ull;
> +		else
> +			return priv->plat_data->bc_rate / 2 * 160ull;

Redundant 'else'.

Do I understand correctly you don't want to fallthrough because it will give
±160 in the rate (depending if it's even or odd)?

> +	case UB953_MODE_NONSYNC_EXT:
> +		/* CLKIN_DIV = 1 always */
> +		return clk_get_rate(priv->clkin) * 80ull;
> +
> +	default:
>  		/* Not supported */
>  		return 0;
>  	}

Tomi Valkeinen June 19, 2023, 9 a.m. UTC | #2

On 16/06/2023 17:47, Andy Shevchenko wrote:
> On Fri, Jun 16, 2023 at 04:59:22PM +0300, Tomi Valkeinen wrote:
>> Add support for FPD-Link non-sync mode with external clock. The only
>> thing that needs to be added is the calculation for the clkout.
> 
> ...
> 
>> +	switch (priv->mode) {
>> +	case UB953_MODE_SYNC:
>> +		if (priv->hw_data->is_ub971)
>> +			return priv->plat_data->bc_rate * 160ull;
>> +		else
>> +			return priv->plat_data->bc_rate / 2 * 160ull;
> 
> Redundant 'else'.

True, but I like the symmetry in:

if (foo)
	return 123;
else
	return 321;

> Do I understand correctly you don't want to fallthrough because it will give
> ±160 in the rate (depending if it's even or odd)?

Sorry, can you clarify? Fallthrough to what?

>> +	case UB953_MODE_NONSYNC_EXT:
>> +		/* CLKIN_DIV = 1 always */
>> +		return clk_get_rate(priv->clkin) * 80ull;
>> +
>> +	default:
>>   		/* Not supported */
>>   		return 0;
>>   	}
>

Andy Shevchenko June 19, 2023, 10:48 a.m. UTC | #3

On Mon, Jun 19, 2023 at 12:00:57PM +0300, Tomi Valkeinen wrote:
> On 16/06/2023 17:47, Andy Shevchenko wrote:
> > On Fri, Jun 16, 2023 at 04:59:22PM +0300, Tomi Valkeinen wrote:
> > > Add support for FPD-Link non-sync mode with external clock. The only
> > > thing that needs to be added is the calculation for the clkout.

...

> > > +	switch (priv->mode) {
> > > +	case UB953_MODE_SYNC:
> > > +		if (priv->hw_data->is_ub971)
> > > +			return priv->plat_data->bc_rate * 160ull;
> > > +		else
> > > +			return priv->plat_data->bc_rate / 2 * 160ull;
> > 
> > Redundant 'else'.
> 
> True, but I like the symmetry in:
> 
> if (foo)
> 	return 123;
> else
> 	return 321;

At the same time it will be symmetry with other switch-case(s). That's why the
question about fallthrough below.

> > Do I understand correctly you don't want to fallthrough because it will give
> > ±160 in the rate (depending if it's even or odd)?
> 
> Sorry, can you clarify? Fallthrough to what?

To the below case since '/ 2 * 160 ~= *80'. Why ~ because it might give
off-by-one error due to even/odd input.

> > > +	case UB953_MODE_NONSYNC_EXT:
> > > +		/* CLKIN_DIV = 1 always */
> > > +		return clk_get_rate(priv->clkin) * 80ull;

Tomi Valkeinen June 19, 2023, 10:57 a.m. UTC | #4

On 19/06/2023 13:48, Andy Shevchenko wrote:
> On Mon, Jun 19, 2023 at 12:00:57PM +0300, Tomi Valkeinen wrote:
>> On 16/06/2023 17:47, Andy Shevchenko wrote:
>>> On Fri, Jun 16, 2023 at 04:59:22PM +0300, Tomi Valkeinen wrote:
>>>> Add support for FPD-Link non-sync mode with external clock. The only
>>>> thing that needs to be added is the calculation for the clkout.
> 
> ...
> 
>>>> +	switch (priv->mode) {
>>>> +	case UB953_MODE_SYNC:
>>>> +		if (priv->hw_data->is_ub971)
>>>> +			return priv->plat_data->bc_rate * 160ull;
>>>> +		else
>>>> +			return priv->plat_data->bc_rate / 2 * 160ull;
>>>
>>> Redundant 'else'.
>>
>> True, but I like the symmetry in:
>>
>> if (foo)
>> 	return 123;
>> else
>> 	return 321;
> 
> At the same time it will be symmetry with other switch-case(s). That's why the
> question about fallthrough below.
> 
>>> Do I understand correctly you don't want to fallthrough because it will give
>>> ±160 in the rate (depending if it's even or odd)?
>>
>> Sorry, can you clarify? Fallthrough to what?
> 
> To the below case since '/ 2 * 160 ~= *80'. Why ~ because it might give
> off-by-one error due to even/odd input.

The below case is different. "priv->plat_data->bc_rate" vs 
"clk_get_rate(priv->clkin)".

As to the order of the calculation (/ 2 * 160 versus * 160 / 2), 
generally speaking, I have never figured out what are the correct ways 
to calculate clock rates.

I wrote "x / 2 * 160" as that's what the documentation gives (there's a 
hardware /2 divider in non-ub971 chips, followed by a 160 multiplier). 
But does the documentation presume that the calculation is done 
precisely, not in integers? If so, "x * 160 / 2" would be better (but 
then, do we need to round?). Or does the /2 hardware divider basically 
actually work as a an integer division, in case "x / 2 * 160" is the 
correct one.

>>>> +	case UB953_MODE_NONSYNC_EXT:
>>>> +		/* CLKIN_DIV = 1 always */
>>>> +		return clk_get_rate(priv->clkin) * 80ull;
> 

  Tomi

diff mbox series

Patch

diff --git a/drivers/media/i2c/ds90ub953.c b/drivers/media/i2c/ds90ub953.c
index ff55740965eb..ae90a647489a 100644
--- a/drivers/media/i2c/ds90ub953.c
+++ b/drivers/media/i2c/ds90ub953.c
@@ -143,6 +143,7 @@  struct ub953_data {
 
 	struct i2c_client	*client;
 	struct regmap		*regmap;
+	struct clk		*clkin;
 
 	u32			num_data_lanes;
 	bool			non_cont_clk;
@@ -842,15 +843,21 @@  static int ub953_i2c_master_init(struct ub953_data *priv)
 
 static u64 ub953_get_fc_rate(struct ub953_data *priv)
 {
-	if (priv->mode != UB953_MODE_SYNC) {
+	switch (priv->mode) {
+	case UB953_MODE_SYNC:
+		if (priv->hw_data->is_ub971)
+			return priv->plat_data->bc_rate * 160ull;
+		else
+			return priv->plat_data->bc_rate / 2 * 160ull;
+
+	case UB953_MODE_NONSYNC_EXT:
+		/* CLKIN_DIV = 1 always */
+		return clk_get_rate(priv->clkin) * 80ull;
+
+	default:
 		/* Not supported */
 		return 0;
 	}
-
-	if (priv->hw_data->is_ub971)
-		return priv->plat_data->bc_rate * 160ull;
-	else
-		return priv->plat_data->bc_rate / 2 * 160ull;
 }
 
 static unsigned long ub953_calc_clkout_ub953(struct ub953_data *priv,
@@ -1189,9 +1196,15 @@  static int ub953_hw_init(struct ub953_data *priv)
 	dev_dbg(dev, "mode from %s: %#x\n", mode_override ? "reg" : "strap",
 		priv->mode);
 
-	if (priv->mode != UB953_MODE_SYNC)
+	if (priv->mode != UB953_MODE_SYNC &&
+	    priv->mode != UB953_MODE_NONSYNC_EXT)
 		return dev_err_probe(dev, -ENODEV,
-				     "Only synchronous mode supported\n");
+				     "Unsupported mode selected: %d\n",
+				     priv->mode);
+
+	if (priv->mode == UB953_MODE_NONSYNC_EXT && !priv->clkin)
+		return dev_err_probe(dev, -EINVAL,
+				     "clkin required for non-sync ext mode\n");
 
 	ret = ub953_read(priv, UB953_REG_REV_MASK_ID, &v);
 	if (ret)
@@ -1319,6 +1332,11 @@  static int ub953_probe(struct i2c_client *client)
 		goto err_mutex_destroy;
 	}
 
+	priv->clkin = devm_clk_get_optional(dev, "clkin");
+	if (IS_ERR(priv->clkin))
+		return dev_err_probe(dev, PTR_ERR(priv->clkin),
+				     "failed to parse 'clkin'\n");
+
 	ret = ub953_parse_dt(priv);
 	if (ret)
 		goto err_mutex_destroy;