[PATCH v4 2/3] iio: adc: vf610: implement configurable conversion modes

Stefan Agner stefan at agner.ch
Sat Mar 28 05:49:52 PDT 2015 

On 2015-03-28 13:07, Jonathan Cameron wrote:
> On 24/03/15 12:47, Stefan Agner wrote:
>> Support configurable conversion mode through sysfs. So far, the
>> mode used was low-power, which is enabled by default now. Beside
>> that, the modes normal and high-speed are selectable as well.
>>
>> Use the new device tree property which specifies the maximum ADC
>> conversion clock frequencies. Depending on the mode used, the
>> available resulting conversion frequency are calculated
>> dynamically.
>>
> One trivial bit inline, otherwise looks good to me.
> I wish there was a better way of 'hinting' to drivers what power mode
> is required, but in the absense of this I guess explicit control is
> all we can do.

An implicit implementation would be possible by just calculating all
frequencies for the three power modes. The driver would then select the
right power mode to get the individual frequencies. However, due to the
nature of sampling timing of the different modes, the frequencies of the
individual modes would overlap over a large range. For the user it would
not be possible to tell which frequency leads to which mode... Hence I
like this implementation more...

>> Acked-by: Fugang Duan <B38611 at freescale.com>
>> Signed-off-by: Stefan Agner <stefan at agner.ch>
>> ---
>>  Documentation/ABI/testing/sysfs-bus-iio-vf610      |   7 +
>>  .../devicetree/bindings/iio/adc/vf610-adc.txt      |   9 ++
>>  drivers/iio/adc/vf610_adc.c                        | 146 +++++++++++++++------
>>  3 files changed, 120 insertions(+), 42 deletions(-)
>>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-vf610
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-vf610 b/Documentation/ABI/testing/sysfs-bus-iio-vf610
>> new file mode 100644
>> index 0000000..85fd0ecd5
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-vf610
>> @@ -0,0 +1,7 @@
>> +What:		/sys/bus/iio/devices/iio:deviceX/conversion_mode
>> +KernelVersion:	4.1
>> +Contact:	linux-iio at vger.kernel.org
>> +Description:
>> +		Specifies the hardware conversion mode used. The three
>> +		available modes are "normal", "high-speed" and "low-power",
>> +		whereas the last is the default mode.
> Fussy English of the day.  where rather than whereas (whereas is only
> used if you say something like. A is normally the case, whereas here B
> is the case)

Ok, got it, thx for pointing that out.

> I like the default that isn't 'normal' :)

Hehe, like that too. The driver historically used the low power mode by
default, and it is probably fine for most application, hence I just kept
that.

What didn't came out by your comment above, do you expect me to do
another revision or did you applied the patch?

--
Stefan

> 
>> diff --git a/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt b/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
>> index 1a4a43d..3eb40e2 100644
>> --- a/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
>> +++ b/Documentation/devicetree/bindings/iio/adc/vf610-adc.txt
>> @@ -11,6 +11,13 @@ Required properties:
>>  - clock-names: Must contain "adc", matching entry in the clocks property.
>>  - vref-supply: The regulator supply ADC reference voltage.
>>
>> +Recommended properties:
>> +- fsl,adck-max-frequency: Maximum frequencies according to datasheets operating
>> +  requirements. Three values are required, depending on conversion mode:
>> +  - Frequency in normal mode (ADLPC=0, ADHSC=0)
>> +  - Frequency in high-speed mode (ADLPC=0, ADHSC=1)
>> +  - Frequency in low-power mode (ADLPC=1, ADHSC=0)
>> +
>>  Example:
>>  adc0: adc at 4003b000 {
>>  	compatible = "fsl,vf610-adc";
>> @@ -18,5 +25,7 @@ adc0: adc at 4003b000 {
>>  	interrupts = <0 53 0x04>;
>>  	clocks = <&clks VF610_CLK_ADC0>;
>>  	clock-names = "adc";
>> +	fsl,adck-max-frequency = <30000000>, <40000000>,
>> +				<20000000>;
>>  	vref-supply = <&reg_vcc_3v3_mcu>;
>>  };
>> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
>> index e63b8e7..b5f94ab8 100644
>> --- a/drivers/iio/adc/vf610_adc.c
>> +++ b/drivers/iio/adc/vf610_adc.c
>> @@ -118,15 +118,21 @@ enum average_sel {
>>  	VF610_ADC_SAMPLE_32,
>>  };
>>
>> +enum conversion_mode_sel {
>> +	VF610_ADC_CONV_NORMAL,
>> +	VF610_ADC_CONV_HIGH_SPEED,
>> +	VF610_ADC_CONV_LOW_POWER,
>> +};
>> +
>>  struct vf610_adc_feature {
>>  	enum clk_sel	clk_sel;
>>  	enum vol_ref	vol_ref;
>> +	enum conversion_mode_sel conv_mode;
>>
>>  	int	clk_div;
>>  	int     sample_rate;
>>  	int	res_mode;
>>
>> -	bool	lpm;
>>  	bool	calibration;
>>  	bool	ovwren;
>>  };
>> @@ -139,6 +145,8 @@ struct vf610_adc {
>>  	u32 vref_uv;
>>  	u32 value;
>>  	struct regulator *vref;
>> +
>> +	u32 max_adck_rate[3];
>>  	struct vf610_adc_feature adc_feature;
>>
>>  	u32 sample_freq_avail[5];
>> @@ -148,46 +156,22 @@ struct vf610_adc {
>>
>>  static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
>>
>> -#define VF610_ADC_CHAN(_idx, _chan_type) {			\
>> -	.type = (_chan_type),					\
>> -	.indexed = 1,						\
>> -	.channel = (_idx),					\
>> -	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
>> -	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |	\
>> -				BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
>> -}
>> -
>> -#define VF610_ADC_TEMPERATURE_CHAN(_idx, _chan_type) {	\
>> -	.type = (_chan_type),	\
>> -	.channel = (_idx),		\
>> -	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),	\
>> -}
>> -
>> -static const struct iio_chan_spec vf610_adc_iio_channels[] = {
>> -	VF610_ADC_CHAN(0, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(1, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(2, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(3, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(4, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(5, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(6, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(7, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(8, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(9, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(10, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(11, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(12, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(13, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(14, IIO_VOLTAGE),
>> -	VF610_ADC_CHAN(15, IIO_VOLTAGE),
>> -	VF610_ADC_TEMPERATURE_CHAN(26, IIO_TEMP),
>> -	/* sentinel */
>> -};
>> -
>>  static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>>  {
>> +	struct vf610_adc_feature *adc_feature = &info->adc_feature;
>>  	unsigned long adck_rate, ipg_rate = clk_get_rate(info->clk);
>> -	int i;
>> +	int divisor, i;
>> +
>> +	adck_rate = info->max_adck_rate[adc_feature->conv_mode];
>> +
>> +	if (adck_rate) {
>> +		/* calculate clk divider which is within specification */
>> +		divisor = ipg_rate / adck_rate;
>> +		adc_feature->clk_div = 1 << fls(divisor + 1);
>> +	} else {
>> +		/* fall-back value using a safe divisor */
>> +		adc_feature->clk_div = 8;
>> +	}
>>
>>  	/*
>>  	 * Calculate ADC sample frequencies
>> @@ -219,10 +203,8 @@ static inline void vf610_adc_cfg_init(struct vf610_adc *info)
>>
>>  	adc_feature->res_mode = 12;
>>  	adc_feature->sample_rate = 1;
>> -	adc_feature->lpm = true;
>>
>> -	/* Use a save ADCK which is below 20MHz on all devices */
>> -	adc_feature->clk_div = 8;
>> +	adc_feature->conv_mode = VF610_ADC_CONV_LOW_POWER;
>>
>>  	vf610_adc_calculate_rates(info);
>>  }
>> @@ -307,10 +289,12 @@ static void vf610_adc_cfg_set(struct vf610_adc *info)
>>  	cfg_data = readl(info->regs + VF610_REG_ADC_CFG);
>>
>>  	cfg_data &= ~VF610_ADC_ADLPC_EN;
>> -	if (adc_feature->lpm)
>> +	if (adc_feature->conv_mode == VF610_ADC_CONV_LOW_POWER)
>>  		cfg_data |= VF610_ADC_ADLPC_EN;
>>
>>  	cfg_data &= ~VF610_ADC_ADHSC_EN;
>> +	if (adc_feature->conv_mode == VF610_ADC_CONV_HIGH_SPEED)
>> +		cfg_data |= VF610_ADC_ADHSC_EN;
>>
>>  	writel(cfg_data, info->regs + VF610_REG_ADC_CFG);
>>  }
>> @@ -412,6 +396,81 @@ static void vf610_adc_hw_init(struct vf610_adc *info)
>>  	vf610_adc_cfg_set(info);
>>  }
>>
>> +static int vf610_set_conversion_mode(struct iio_dev *indio_dev,
>> +				     const struct iio_chan_spec *chan,
>> +				     unsigned int mode)
>> +{
>> +	struct vf610_adc *info = iio_priv(indio_dev);
>> +
>> +	mutex_lock(&indio_dev->mlock);
>> +	info->adc_feature.conv_mode = mode;
>> +	vf610_adc_calculate_rates(info);
>> +	vf610_adc_hw_init(info);
>> +	mutex_unlock(&indio_dev->mlock);
>> +
>> +	return 0;
>> +}
>> +
>> +static int vf610_get_conversion_mode(struct iio_dev *indio_dev,
>> +				     const struct iio_chan_spec *chan)
>> +{
>> +	struct vf610_adc *info = iio_priv(indio_dev);
>> +
>> +	return info->adc_feature.conv_mode;
>> +}
>> +
>> +static const char * const vf610_conv_modes[] = { "normal", "high-speed",
>> +						 "low-power" };
>> +
>> +static const struct iio_enum vf610_conversion_mode = {
>> +	.items = vf610_conv_modes,
>> +	.num_items = ARRAY_SIZE(vf610_conv_modes),
>> +	.get = vf610_get_conversion_mode,
>> +	.set = vf610_set_conversion_mode,
>> +};
>> +
>> +static const struct iio_chan_spec_ext_info vf610_ext_info[] = {
>> +	IIO_ENUM("conversion_mode", IIO_SHARED_BY_DIR, &vf610_conversion_mode),
>> +	{},
>> +};
>> +
>> +#define VF610_ADC_CHAN(_idx, _chan_type) {			\
>> +	.type = (_chan_type),					\
>> +	.indexed = 1,						\
>> +	.channel = (_idx),					\
>> +	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
>> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |	\
>> +				BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
>> +	.ext_info = vf610_ext_info,				\
>> +}
>> +
>> +#define VF610_ADC_TEMPERATURE_CHAN(_idx, _chan_type) {	\
>> +	.type = (_chan_type),	\
>> +	.channel = (_idx),		\
>> +	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),	\
>> +}
>> +
>> +static const struct iio_chan_spec vf610_adc_iio_channels[] = {
>> +	VF610_ADC_CHAN(0, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(1, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(2, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(3, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(4, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(5, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(6, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(7, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(8, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(9, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(10, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(11, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(12, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(13, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(14, IIO_VOLTAGE),
>> +	VF610_ADC_CHAN(15, IIO_VOLTAGE),
>> +	VF610_ADC_TEMPERATURE_CHAN(26, IIO_TEMP),
>> +	/* sentinel */
>> +};
>> +
>>  static int vf610_adc_read_data(struct vf610_adc *info)
>>  {
>>  	int result;
>> @@ -654,6 +713,9 @@ static int vf610_adc_probe(struct platform_device *pdev)
>>
>>  	info->vref_uv = regulator_get_voltage(info->vref);
>>
>> +	of_property_read_u32_array(pdev->dev.of_node, "fsl,adck-max-frequency",
>> +			info->max_adck_rate, 3);
>> +
>>  	platform_set_drvdata(pdev, indio_dev);
>>
>>  	init_completion(&info->completion);
>>

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