[PATCH 0/3] iio: adc: vf610: respect ADC clocking limitations

[PATCH 0/3] iio: adc: vf610: respect ADC clocking limitations

[Stefan Agner]

Respect ADC clocking limitations which lead to bogous reading on
500MHz clocked Vybrid SoC's. Additionally, also implement a
sysfs-property to configure the conversion mode available in this
ADC peripherial.

Stefan Agner (3):
  iio: adc: vf610: use ADC clock within specification
  iio: adc: vf610: implement configurable conversion modes
  ARM: dts: add property for maximum ADC clock frequencies

 .../devicetree/bindings/iio/adc/vf610-adc.txt      |   9 ++
 arch/arm/boot/dts/vfxxx.dtsi                       |   4 +
 drivers/iio/adc/vf610_adc.c                        | 175 +++++++++++++++++----
 3 files changed, 156 insertions(+), 32 deletions(-)

-- 
2.2.2

[PATCH 1/3] iio: adc: vf610: use ADC clock within specification

[Stefan Agner]

Depending on conversion mode used, the ADC clock (ADCK) needs
to be below a maximum frequency. According to Vybrid's data
sheet this is 20MHz for the low power conversion mode.

The ADC clock is depending on input clock, which is the bus
clock by default. Vybrid SoC are typically clocked at at 400MHz
or 500MHz, which leads to 66MHz or 83MHz bus clock respectively.
Hence, a divider of 8 is required to stay below the specified
maximum clock of 20MHz.

Due to the different bus clock speeds, the resulting sampling
frequency is not static. Hence use the ADC clock and calculate
the actual available sampling frequency dynamically.

This fixes bogous values observed on some 500MHz clocked Vybrid
SoC. The resulting value usually showed Bit 9 being stuck at 1,
or 0, which lead to a value of +/-512.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/iio/adc/vf610_adc.c | 91 ++++++++++++++++++++++++++++++---------------
 1 file changed, 61 insertions(+), 30 deletions(-)

diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
index 8ec353c..e63b8e7 100644
--- a/drivers/iio/adc/vf610_adc.c
+++ b/drivers/iio/adc/vf610_adc.c
@@ -141,9 +141,13 @@ struct vf610_adc {
 	struct regulator *vref;
 	struct vf610_adc_feature adc_feature;
 
+	u32 sample_freq_avail[5];
+
 	struct completion completion;
 };
 
+static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
+
 #define VF610_ADC_CHAN(_idx, _chan_type) {			\
 	.type = (_chan_type),					\
 	.indexed = 1,						\
@@ -180,35 +184,47 @@ static const struct iio_chan_spec vf610_adc_iio_channels[] = {
 	/* sentinel */
 };
 
-/*
- * ADC sample frequency, unit is ADCK cycles.
- * ADC clk source is ipg clock, which is the same as bus clock.
- *
- * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
- * SFCAdder: fixed to 6 ADCK cycles
- * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
- * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
- * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
- *
- * By default, enable 12 bit resolution mode, clock source
- * set to ipg clock, So get below frequency group:
- */
-static const u32 vf610_sample_freq_avail[5] =
-{1941176, 559332, 286957, 145374, 73171};
+static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
+{
+	unsigned long adck_rate, ipg_rate = clk_get_rate(info->clk);
+	int i;
+
+	/*
+	 * Calculate ADC sample frequencies
+	 * Sample time unit is ADCK cycles. ADCK clk source is ipg clock,
+	 * which is the same as bus clock.
+	 *
+	 * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
+	 * SFCAdder: fixed to 6 ADCK cycles
+	 * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
+	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
+	 * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
+	 */
+	adck_rate = ipg_rate / info->adc_feature.clk_div;
+	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
+		info->sample_freq_avail[i] =
+			adck_rate / (6 + vf610_hw_avgs[i] * (25 + 3));
+}
 
 static inline void vf610_adc_cfg_init(struct vf610_adc *info)
 {
+	struct vf610_adc_feature *adc_feature = &info->adc_feature;
+
 	/* set default Configuration for ADC controller */
-	info->adc_feature.clk_sel = VF610_ADCIOC_BUSCLK_SET;
-	info->adc_feature.vol_ref = VF610_ADCIOC_VR_VREF_SET;
+	adc_feature->clk_sel = VF610_ADCIOC_BUSCLK_SET;
+	adc_feature->vol_ref = VF610_ADCIOC_VR_VREF_SET;
+
+	adc_feature->calibration = true;
+	adc_feature->ovwren = true;
+
+	adc_feature->res_mode = 12;
+	adc_feature->sample_rate = 1;
+	adc_feature->lpm = true;
 
-	info->adc_feature.calibration = true;
-	info->adc_feature.ovwren = true;
+	/* Use a save ADCK which is below 20MHz on all devices */
+	adc_feature->clk_div = 8;
 
-	info->adc_feature.clk_div = 1;
-	info->adc_feature.res_mode = 12;
-	info->adc_feature.sample_rate = 1;
-	info->adc_feature.lpm = true;
+	vf610_adc_calculate_rates(info);
 }
 
 static void vf610_adc_cfg_post_set(struct vf610_adc *info)
@@ -290,12 +306,10 @@ static void vf610_adc_cfg_set(struct vf610_adc *info)
 
 	cfg_data = readl(info->regs + VF610_REG_ADC_CFG);
 
-	/* low power configuration */
 	cfg_data &= ~VF610_ADC_ADLPC_EN;
 	if (adc_feature->lpm)
 		cfg_data |= VF610_ADC_ADLPC_EN;
 
-	/* disable high speed */
 	cfg_data &= ~VF610_ADC_ADHSC_EN;
 
 	writel(cfg_data, info->regs + VF610_REG_ADC_CFG);
@@ -435,10 +449,27 @@ static irqreturn_t vf610_adc_isr(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("1941176, 559332, 286957, 145374, 73171");
+static ssize_t vf610_show_samp_freq_avail(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct vf610_adc *info = iio_priv(dev_to_iio_dev(dev));
+	size_t len = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(info->sample_freq_avail); i++)
+		len += scnprintf(buf + len, PAGE_SIZE - len,
+			"%u ", info->sample_freq_avail[i]);
+
+	/* replace trailing space by newline */
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(vf610_show_samp_freq_avail);
 
 static struct attribute *vf610_attributes[] = {
-	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
+	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
 	NULL
 };
 
@@ -502,7 +533,7 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
 		return IIO_VAL_FRACTIONAL_LOG2;
 
 	case IIO_CHAN_INFO_SAMP_FREQ:
-		*val = vf610_sample_freq_avail[info->adc_feature.sample_rate];
+		*val = info->sample_freq_avail[info->adc_feature.sample_rate];
 		*val2 = 0;
 		return IIO_VAL_INT;
 
@@ -525,9 +556,9 @@ static int vf610_write_raw(struct iio_dev *indio_dev,
 	switch (mask) {
 		case IIO_CHAN_INFO_SAMP_FREQ:
 			for (i = 0;
-				i < ARRAY_SIZE(vf610_sample_freq_avail);
+				i < ARRAY_SIZE(info->sample_freq_avail);
 				i++)
-				if (val == vf610_sample_freq_avail[i]) {
+				if (val == info->sample_freq_avail[i]) {
 					info->adc_feature.sample_rate = i;
 					vf610_adc_sample_set(info);
 					return 0;
-- 
2.2.2

[PATCH 1/3] iio: adc: vf610: use ADC clock within specification

[Jonathan Cameron]

On 20/01/15 16:02, Stefan Agner wrote:
> Depending on conversion mode used, the ADC clock (ADCK) needs
> to be below a maximum frequency. According to Vybrid's data
> sheet this is 20MHz for the low power conversion mode.
> 
> The ADC clock is depending on input clock, which is the bus
> clock by default. Vybrid SoC are typically clocked at at 400MHz
> or 500MHz, which leads to 66MHz or 83MHz bus clock respectively.
> Hence, a divider of 8 is required to stay below the specified
> maximum clock of 20MHz.
I hate to point out the obvious, by 83/8 > 20.  Missing something?
> 
> Due to the different bus clock speeds, the resulting sampling
> frequency is not static. Hence use the ADC clock and calculate
> the actual available sampling frequency dynamically.
> 
> This fixes bogous values observed on some 500MHz clocked Vybrid
> SoC. The resulting value usually showed Bit 9 being stuck at 1,
> or 0, which lead to a value of +/-512.
> 
> Signed-off-by: Stefan Agner <stefan@agner.ch>
In principle this looks fine to me. I would however like an
Ack from Fugang as the original author of the driver).

Given timing I probably wouldn't send this upstream until after
the merge window now (as it's stable material this won't really
matter).

Jonathan
> ---
>  drivers/iio/adc/vf610_adc.c | 91 ++++++++++++++++++++++++++++++---------------
>  1 file changed, 61 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
> index 8ec353c..e63b8e7 100644
> --- a/drivers/iio/adc/vf610_adc.c
> +++ b/drivers/iio/adc/vf610_adc.c
> @@ -141,9 +141,13 @@ struct vf610_adc {
>  	struct regulator *vref;
>  	struct vf610_adc_feature adc_feature;
>  
> +	u32 sample_freq_avail[5];
> +
>  	struct completion completion;
>  };
>  
> +static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
> +
>  #define VF610_ADC_CHAN(_idx, _chan_type) {			\
>  	.type = (_chan_type),					\
>  	.indexed = 1,						\
> @@ -180,35 +184,47 @@ static const struct iio_chan_spec vf610_adc_iio_channels[] = {
>  	/* sentinel */
>  };
>  
> -/*
> - * ADC sample frequency, unit is ADCK cycles.
> - * ADC clk source is ipg clock, which is the same as bus clock.
> - *
> - * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
> - * SFCAdder: fixed to 6 ADCK cycles
> - * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
> - * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
> - * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
> - *
> - * By default, enable 12 bit resolution mode, clock source
> - * set to ipg clock, So get below frequency group:
> - */
> -static const u32 vf610_sample_freq_avail[5] =
> -{1941176, 559332, 286957, 145374, 73171};
> +static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
> +{
> +	unsigned long adck_rate, ipg_rate = clk_get_rate(info->clk);
> +	int i;
> +
> +	/*
> +	 * Calculate ADC sample frequencies
> +	 * Sample time unit is ADCK cycles. ADCK clk source is ipg clock,
> +	 * which is the same as bus clock.
> +	 *
> +	 * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
> +	 * SFCAdder: fixed to 6 ADCK cycles
> +	 * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
> +	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
> +	 * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
> +	 */
> +	adck_rate = ipg_rate / info->adc_feature.clk_div;
> +	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
> +		info->sample_freq_avail[i] =
> +			adck_rate / (6 + vf610_hw_avgs[i] * (25 + 3));
> +}
>  
>  static inline void vf610_adc_cfg_init(struct vf610_adc *info)
>  {
> +	struct vf610_adc_feature *adc_feature = &info->adc_feature;
> +
>  	/* set default Configuration for ADC controller */
> -	info->adc_feature.clk_sel = VF610_ADCIOC_BUSCLK_SET;
> -	info->adc_feature.vol_ref = VF610_ADCIOC_VR_VREF_SET;
> +	adc_feature->clk_sel = VF610_ADCIOC_BUSCLK_SET;
> +	adc_feature->vol_ref = VF610_ADCIOC_VR_VREF_SET;
> +
> +	adc_feature->calibration = true;
> +	adc_feature->ovwren = true;
> +
> +	adc_feature->res_mode = 12;
> +	adc_feature->sample_rate = 1;
> +	adc_feature->lpm = true;
>  
> -	info->adc_feature.calibration = true;
> -	info->adc_feature.ovwren = true;
> +	/* Use a save ADCK which is below 20MHz on all devices */
> +	adc_feature->clk_div = 8;
>  
> -	info->adc_feature.clk_div = 1;
> -	info->adc_feature.res_mode = 12;
> -	info->adc_feature.sample_rate = 1;
> -	info->adc_feature.lpm = true;
> +	vf610_adc_calculate_rates(info);
>  }
>  
>  static void vf610_adc_cfg_post_set(struct vf610_adc *info)
> @@ -290,12 +306,10 @@ static void vf610_adc_cfg_set(struct vf610_adc *info)
>  
>  	cfg_data = readl(info->regs + VF610_REG_ADC_CFG);
>  
> -	/* low power configuration */
>  	cfg_data &= ~VF610_ADC_ADLPC_EN;
>  	if (adc_feature->lpm)
>  		cfg_data |= VF610_ADC_ADLPC_EN;
>  
> -	/* disable high speed */
>  	cfg_data &= ~VF610_ADC_ADHSC_EN;
>  
>  	writel(cfg_data, info->regs + VF610_REG_ADC_CFG);
> @@ -435,10 +449,27 @@ static irqreturn_t vf610_adc_isr(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>  
> -static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("1941176, 559332, 286957, 145374, 73171");
> +static ssize_t vf610_show_samp_freq_avail(struct device *dev,
> +				struct device_attribute *attr, char *buf)
> +{
> +	struct vf610_adc *info = iio_priv(dev_to_iio_dev(dev));
> +	size_t len = 0;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(info->sample_freq_avail); i++)
> +		len += scnprintf(buf + len, PAGE_SIZE - len,
> +			"%u ", info->sample_freq_avail[i]);
> +
> +	/* replace trailing space by newline */
> +	buf[len - 1] = '\n';
> +
> +	return len;
> +}
> +
> +static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(vf610_show_samp_freq_avail);
>  
>  static struct attribute *vf610_attributes[] = {
> -	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
> +	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
>  	NULL
>  };
>  
> @@ -502,7 +533,7 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
>  		return IIO_VAL_FRACTIONAL_LOG2;
>  
>  	case IIO_CHAN_INFO_SAMP_FREQ:
> -		*val = vf610_sample_freq_avail[info->adc_feature.sample_rate];
> +		*val = info->sample_freq_avail[info->adc_feature.sample_rate];
>  		*val2 = 0;
>  		return IIO_VAL_INT;
>  
> @@ -525,9 +556,9 @@ static int vf610_write_raw(struct iio_dev *indio_dev,
>  	switch (mask) {
>  		case IIO_CHAN_INFO_SAMP_FREQ:
>  			for (i = 0;
> -				i < ARRAY_SIZE(vf610_sample_freq_avail);
> +				i < ARRAY_SIZE(info->sample_freq_avail);
>  				i++)
> -				if (val == vf610_sample_freq_avail[i]) {
> +				if (val == info->sample_freq_avail[i]) {
>  					info->adc_feature.sample_rate = i;
>  					vf610_adc_sample_set(info);
>  					return 0;
> 

[PATCH 1/3] iio: adc: vf610: use ADC clock within specification

[Stefan Agner]

On 2015-01-27 21:59, Jonathan Cameron wrote:
> On 20/01/15 16:02, Stefan Agner wrote:
>> Depending on conversion mode used, the ADC clock (ADCK) needs
>> to be below a maximum frequency. According to Vybrid's data
>> sheet this is 20MHz for the low power conversion mode.
>>
>> The ADC clock is depending on input clock, which is the bus
>> clock by default. Vybrid SoC are typically clocked at at 400MHz
>> or 500MHz, which leads to 66MHz or 83MHz bus clock respectively.
>> Hence, a divider of 8 is required to stay below the specified
>> maximum clock of 20MHz.
> I hate to point out the obvious, by 83/8 > 20.  Missing something?

"stay below the specified maximum clock of 20MHz."
                          ^

The next smaller divider is 4, but then we would en up with more than
20MHz... Unfortunate, but I really don't want to violate the spec :-)

>>
>> Due to the different bus clock speeds, the resulting sampling
>> frequency is not static. Hence use the ADC clock and calculate
>> the actual available sampling frequency dynamically.
>>
>> This fixes bogous values observed on some 500MHz clocked Vybrid
>> SoC. The resulting value usually showed Bit 9 being stuck at 1,
>> or 0, which lead to a value of +/-512.
>>
>> Signed-off-by: Stefan Agner <stefan@agner.ch>
> In principle this looks fine to me. I would however like an
> Ack from Fugang as the original author of the driver).

Ok, Fugang is in CC too (B38611 at freescale.com).


> Given timing I probably wouldn't send this upstream until after
> the merge window now (as it's stable material this won't really
> matter).

That's fine for me, thx.

--
Stefan

> 
> Jonathan
>> ---
>>  drivers/iio/adc/vf610_adc.c | 91 ++++++++++++++++++++++++++++++---------------
>>  1 file changed, 61 insertions(+), 30 deletions(-)
>>
>> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
>> index 8ec353c..e63b8e7 100644
>> --- a/drivers/iio/adc/vf610_adc.c
>> +++ b/drivers/iio/adc/vf610_adc.c
>> @@ -141,9 +141,13 @@ struct vf610_adc {
>>  	struct regulator *vref;
>>  	struct vf610_adc_feature adc_feature;
>>
>> +	u32 sample_freq_avail[5];
>> +
>>  	struct completion completion;
>>  };
>>
>> +static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
>> +
>>  #define VF610_ADC_CHAN(_idx, _chan_type) {			\
>>  	.type = (_chan_type),					\
>>  	.indexed = 1,						\
>> @@ -180,35 +184,47 @@ static const struct iio_chan_spec vf610_adc_iio_channels[] = {
>>  	/* sentinel */
>>  };
>>
>> -/*
>> - * ADC sample frequency, unit is ADCK cycles.
>> - * ADC clk source is ipg clock, which is the same as bus clock.
>> - *
>> - * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
>> - * SFCAdder: fixed to 6 ADCK cycles
>> - * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
>> - * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
>> - * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
>> - *
>> - * By default, enable 12 bit resolution mode, clock source
>> - * set to ipg clock, So get below frequency group:
>> - */
>> -static const u32 vf610_sample_freq_avail[5] =
>> -{1941176, 559332, 286957, 145374, 73171};
>> +static inline void vf610_adc_calculate_rates(struct vf610_adc *info)
>> +{
>> +	unsigned long adck_rate, ipg_rate = clk_get_rate(info->clk);
>> +	int i;
>> +
>> +	/*
>> +	 * Calculate ADC sample frequencies
>> +	 * Sample time unit is ADCK cycles. ADCK clk source is ipg clock,
>> +	 * which is the same as bus clock.
>> +	 *
>> +	 * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
>> +	 * SFCAdder: fixed to 6 ADCK cycles
>> +	 * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
>> +	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit mode
>> +	 * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
>> +	 */
>> +	adck_rate = ipg_rate / info->adc_feature.clk_div;
>> +	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
>> +		info->sample_freq_avail[i] =
>> +			adck_rate / (6 + vf610_hw_avgs[i] * (25 + 3));
>> +}
>>
>>  static inline void vf610_adc_cfg_init(struct vf610_adc *info)
>>  {
>> +	struct vf610_adc_feature *adc_feature = &info->adc_feature;
>> +
>>  	/* set default Configuration for ADC controller */
>> -	info->adc_feature.clk_sel = VF610_ADCIOC_BUSCLK_SET;
>> -	info->adc_feature.vol_ref = VF610_ADCIOC_VR_VREF_SET;
>> +	adc_feature->clk_sel = VF610_ADCIOC_BUSCLK_SET;
>> +	adc_feature->vol_ref = VF610_ADCIOC_VR_VREF_SET;
>> +
>> +	adc_feature->calibration = true;
>> +	adc_feature->ovwren = true;
>> +
>> +	adc_feature->res_mode = 12;
>> +	adc_feature->sample_rate = 1;
>> +	adc_feature->lpm = true;
>>
>> -	info->adc_feature.calibration = true;
>> -	info->adc_feature.ovwren = true;
>> +	/* Use a save ADCK which is below 20MHz on all devices */
>> +	adc_feature->clk_div = 8;
>>
>> -	info->adc_feature.clk_div = 1;
>> -	info->adc_feature.res_mode = 12;
>> -	info->adc_feature.sample_rate = 1;
>> -	info->adc_feature.lpm = true;
>> +	vf610_adc_calculate_rates(info);
>>  }
>>
>>  static void vf610_adc_cfg_post_set(struct vf610_adc *info)
>> @@ -290,12 +306,10 @@ static void vf610_adc_cfg_set(struct vf610_adc *info)
>>
>>  	cfg_data = readl(info->regs + VF610_REG_ADC_CFG);
>>
>> -	/* low power configuration */
>>  	cfg_data &= ~VF610_ADC_ADLPC_EN;
>>  	if (adc_feature->lpm)
>>  		cfg_data |= VF610_ADC_ADLPC_EN;
>>
>> -	/* disable high speed */
>>  	cfg_data &= ~VF610_ADC_ADHSC_EN;
>>
>>  	writel(cfg_data, info->regs + VF610_REG_ADC_CFG);
>> @@ -435,10 +449,27 @@ static irqreturn_t vf610_adc_isr(int irq, void *dev_id)
>>  	return IRQ_HANDLED;
>>  }
>>
>> -static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("1941176, 559332, 286957, 145374, 73171");
>> +static ssize_t vf610_show_samp_freq_avail(struct device *dev,
>> +				struct device_attribute *attr, char *buf)
>> +{
>> +	struct vf610_adc *info = iio_priv(dev_to_iio_dev(dev));
>> +	size_t len = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < ARRAY_SIZE(info->sample_freq_avail); i++)
>> +		len += scnprintf(buf + len, PAGE_SIZE - len,
>> +			"%u ", info->sample_freq_avail[i]);
>> +
>> +	/* replace trailing space by newline */
>> +	buf[len - 1] = '\n';
>> +
>> +	return len;
>> +}
>> +
>> +static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(vf610_show_samp_freq_avail);
>>
>>  static struct attribute *vf610_attributes[] = {
>> -	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
>> +	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
>>  	NULL
>>  };
>>
>> @@ -502,7 +533,7 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
>>  		return IIO_VAL_FRACTIONAL_LOG2;
>>
>>  	case IIO_CHAN_INFO_SAMP_FREQ:
>> -		*val = vf610_sample_freq_avail[info->adc_feature.sample_rate];
>> +		*val = info->sample_freq_avail[info->adc_feature.sample_rate];
>>  		*val2 = 0;
>>  		return IIO_VAL_INT;
>>
>> @@ -525,9 +556,9 @@ static int vf610_write_raw(struct iio_dev *indio_dev,
>>  	switch (mask) {
>>  		case IIO_CHAN_INFO_SAMP_FREQ:
>>  			for (i = 0;
>> -				i < ARRAY_SIZE(vf610_sample_freq_avail);
>> +				i < ARRAY_SIZE(info->sample_freq_avail);
>>  				i++)
>> -				if (val == vf610_sample_freq_avail[i]) {
>> +				if (val == info->sample_freq_avail[i]) {
>>  					info->adc_feature.sample_rate = i;
>>  					vf610_adc_sample_set(info);
>>  					return 0;
>>

[PATCH 1/3] iio: adc: vf610: use ADC clock within specification

[Jonathan Cameron]

On 27 January 2015 21:20:24 GMT+00:00, Stefan Agner <stefan@agner.ch> wrote:
>On 2015-01-27 21:59, Jonathan Cameron wrote:
>> On 20/01/15 16:02, Stefan Agner wrote:
>>> Depending on conversion mode used, the ADC clock (ADCK) needs
>>> to be below a maximum frequency. According to Vybrid's data
>>> sheet this is 20MHz for the low power conversion mode.
>>>
>>> The ADC clock is depending on input clock, which is the bus
>>> clock by default. Vybrid SoC are typically clocked at at 400MHz
>>> or 500MHz, which leads to 66MHz or 83MHz bus clock respectively.
>>> Hence, a divider of 8 is required to stay below the specified
>>> maximum clock of 20MHz.
>> I hate to point out the obvious, by 83/8 > 20.  Missing something?
>
>"stay below the specified maximum clock of 20MHz."
>                          ^
>
>The next smaller divider is 4, but then we would en up with more than
>20MHz... Unfortunate, but I really don't want to violate the spec :-)
Ignore me. Half asleep. Of course you are correct!
>
>>>
>>> Due to the different bus clock speeds, the resulting sampling
>>> frequency is not static. Hence use the ADC clock and calculate
>>> the actual available sampling frequency dynamically.
>>>
>>> This fixes bogous values observed on some 500MHz clocked Vybrid
>>> SoC. The resulting value usually showed Bit 9 being stuck at 1,
>>> or 0, which lead to a value of +/-512.
>>>
>>> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> In principle this looks fine to me. I would however like an
>> Ack from Fugang as the original author of the driver).
>
>Ok, Fugang is in CC too (B38611 at freescale.com).
>
>
>> Given timing I probably wouldn't send this upstream until after
>> the merge window now (as it's stable material this won't really
>> matter).
>
>That's fine for me, thx.
>
>--
>Stefan
>
>> 
>> Jonathan
>>> ---
>>>  drivers/iio/adc/vf610_adc.c | 91
>++++++++++++++++++++++++++++++---------------
>>>  1 file changed, 61 insertions(+), 30 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/vf610_adc.c
>b/drivers/iio/adc/vf610_adc.c
>>> index 8ec353c..e63b8e7 100644
>>> --- a/drivers/iio/adc/vf610_adc.c
>>> +++ b/drivers/iio/adc/vf610_adc.c
>>> @@ -141,9 +141,13 @@ struct vf610_adc {
>>>  	struct regulator *vref;
>>>  	struct vf610_adc_feature adc_feature;
>>>
>>> +	u32 sample_freq_avail[5];
>>> +
>>>  	struct completion completion;
>>>  };
>>>
>>> +static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
>>> +
>>>  #define VF610_ADC_CHAN(_idx, _chan_type) {			\
>>>  	.type = (_chan_type),					\
>>>  	.indexed = 1,						\
>>> @@ -180,35 +184,47 @@ static const struct iio_chan_spec
>vf610_adc_iio_channels[] = {
>>>  	/* sentinel */
>>>  };
>>>
>>> -/*
>>> - * ADC sample frequency, unit is ADCK cycles.
>>> - * ADC clk source is ipg clock, which is the same as bus clock.
>>> - *
>>> - * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
>>> - * SFCAdder: fixed to 6 ADCK cycles
>>> - * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
>>> - * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit
>mode
>>> - * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
>>> - *
>>> - * By default, enable 12 bit resolution mode, clock source
>>> - * set to ipg clock, So get below frequency group:
>>> - */
>>> -static const u32 vf610_sample_freq_avail[5] =
>>> -{1941176, 559332, 286957, 145374, 73171};
>>> +static inline void vf610_adc_calculate_rates(struct vf610_adc
>*info)
>>> +{
>>> +	unsigned long adck_rate, ipg_rate = clk_get_rate(info->clk);
>>> +	int i;
>>> +
>>> +	/*
>>> +	 * Calculate ADC sample frequencies
>>> +	 * Sample time unit is ADCK cycles. ADCK clk source is ipg clock,
>>> +	 * which is the same as bus clock.
>>> +	 *
>>> +	 * ADC conversion time = SFCAdder + AverageNum x (BCT + LSTAdder)
>>> +	 * SFCAdder: fixed to 6 ADCK cycles
>>> +	 * AverageNum: 1, 4, 8, 16, 32 samples for hardware average.
>>> +	 * BCT (Base Conversion Time): fixed to 25 ADCK cycles for 12 bit
>mode
>>> +	 * LSTAdder(Long Sample Time): fixed to 3 ADCK cycles
>>> +	 */
>>> +	adck_rate = ipg_rate / info->adc_feature.clk_div;
>>> +	for (i = 0; i < ARRAY_SIZE(vf610_hw_avgs); i++)
>>> +		info->sample_freq_avail[i] =
>>> +			adck_rate / (6 + vf610_hw_avgs[i] * (25 + 3));
>>> +}
>>>
>>>  static inline void vf610_adc_cfg_init(struct vf610_adc *info)
>>>  {
>>> +	struct vf610_adc_feature *adc_feature = &info->adc_feature;
>>> +
>>>  	/* set default Configuration for ADC controller */
>>> -	info->adc_feature.clk_sel = VF610_ADCIOC_BUSCLK_SET;
>>> -	info->adc_feature.vol_ref = VF610_ADCIOC_VR_VREF_SET;
>>> +	adc_feature->clk_sel = VF610_ADCIOC_BUSCLK_SET;
>>> +	adc_feature->vol_ref = VF610_ADCIOC_VR_VREF_SET;
>>> +
>>> +	adc_feature->calibration = true;
>>> +	adc_feature->ovwren = true;
>>> +
>>> +	adc_feature->res_mode = 12;
>>> +	adc_feature->sample_rate = 1;
>>> +	adc_feature->lpm = true;
>>>
>>> -	info->adc_feature.calibration = true;
>>> -	info->adc_feature.ovwren = true;
>>> +	/* Use a save ADCK which is below 20MHz on all devices */
>>> +	adc_feature->clk_div = 8;
>>>
>>> -	info->adc_feature.clk_div = 1;
>>> -	info->adc_feature.res_mode = 12;
>>> -	info->adc_feature.sample_rate = 1;
>>> -	info->adc_feature.lpm = true;
>>> +	vf610_adc_calculate_rates(info);
>>>  }
>>>
>>>  static void vf610_adc_cfg_post_set(struct vf610_adc *info)
>>> @@ -290,12 +306,10 @@ static void vf610_adc_cfg_set(struct vf610_adc
>*info)
>>>
>>>  	cfg_data = readl(info->regs + VF610_REG_ADC_CFG);
>>>
>>> -	/* low power configuration */
>>>  	cfg_data &= ~VF610_ADC_ADLPC_EN;
>>>  	if (adc_feature->lpm)
>>>  		cfg_data |= VF610_ADC_ADLPC_EN;
>>>
>>> -	/* disable high speed */
>>>  	cfg_data &= ~VF610_ADC_ADHSC_EN;
>>>
>>>  	writel(cfg_data, info->regs + VF610_REG_ADC_CFG);
>>> @@ -435,10 +449,27 @@ static irqreturn_t vf610_adc_isr(int irq, void
>*dev_id)
>>>  	return IRQ_HANDLED;
>>>  }
>>>
>>> -static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("1941176, 559332, 286957,
>145374, 73171");
>>> +static ssize_t vf610_show_samp_freq_avail(struct device *dev,
>>> +				struct device_attribute *attr, char *buf)
>>> +{
>>> +	struct vf610_adc *info = iio_priv(dev_to_iio_dev(dev));
>>> +	size_t len = 0;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < ARRAY_SIZE(info->sample_freq_avail); i++)
>>> +		len += scnprintf(buf + len, PAGE_SIZE - len,
>>> +			"%u ", info->sample_freq_avail[i]);
>>> +
>>> +	/* replace trailing space by newline */
>>> +	buf[len - 1] = '\n';
>>> +
>>> +	return len;
>>> +}
>>> +
>>> +static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(vf610_show_samp_freq_avail);
>>>
>>>  static struct attribute *vf610_attributes[] = {
>>> -	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
>>> +	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
>>>  	NULL
>>>  };
>>>
>>> @@ -502,7 +533,7 @@ static int vf610_read_raw(struct iio_dev
>*indio_dev,
>>>  		return IIO_VAL_FRACTIONAL_LOG2;
>>>
>>>  	case IIO_CHAN_INFO_SAMP_FREQ:
>>> -		*val = vf610_sample_freq_avail[info->adc_feature.sample_rate];
>>> +		*val = info->sample_freq_avail[info->adc_feature.sample_rate];
>>>  		*val2 = 0;
>>>  		return IIO_VAL_INT;
>>>
>>> @@ -525,9 +556,9 @@ static int vf610_write_raw(struct iio_dev
>*indio_dev,
>>>  	switch (mask) {
>>>  		case IIO_CHAN_INFO_SAMP_FREQ:
>>>  			for (i = 0;
>>> -				i < ARRAY_SIZE(vf610_sample_freq_avail);
>>> +				i < ARRAY_SIZE(info->sample_freq_avail);
>>>  				i++)
>>> -				if (val == vf610_sample_freq_avail[i]) {
>>> +				if (val == info->sample_freq_avail[i]) {
>>>  					info->adc_feature.sample_rate = i;
>>>  					vf610_adc_sample_set(info);
>>>  					return 0;
>>>
>--
>To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>the body of a message to majordomo at vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

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

[Stefan Agner]

Support configureable 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 calcaulated
dynamically.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/iio/adc/vf610_adc.c | 92 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 86 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
index e63b8e7..fd41d91c 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];
@@ -146,6 +154,8 @@ struct vf610_adc {
 	struct completion completion;
 };
 
+static const char * const vf610_conv_modes[] = { "normal", "high-speed",
+						 "low-power" };
 static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
 
 #define VF610_ADC_CHAN(_idx, _chan_type) {			\
@@ -186,8 +196,20 @@ static const struct iio_chan_spec vf610_adc_iio_channels[] = {
 
 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 +241,8 @@ 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 +327,12 @@ 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);
 }
@@ -466,10 +488,65 @@ static ssize_t vf610_show_samp_freq_avail(struct device *dev,
 	return len;
 }
 
+static ssize_t vf610_read_mode(struct device *dev,
+		struct device_attribute *attr,
+		char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct vf610_adc *info = iio_priv(indio_dev);
+
+	return sprintf(buf, "%s\n",
+			vf610_conv_modes[info->adc_feature.conv_mode]);
+}
+
+
+static ssize_t vf610_write_mode(struct device *dev,
+		struct device_attribute *attr,
+		const char *buf,
+		size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct vf610_adc *info = iio_priv(indio_dev);
+	int i, mode = -EINVAL;
+
+	mutex_lock(&indio_dev->mlock);
+	if (iio_buffer_enabled(indio_dev)) {
+		mutex_unlock(&indio_dev->mlock);
+		return -EBUSY;
+	}
+	mutex_unlock(&indio_dev->mlock);
+
+	for (i = 0; i < ARRAY_SIZE(vf610_conv_modes); i++) {
+		if (!strcmp(vf610_conv_modes[i], buf)) {
+			mode = i;
+			break;
+		}
+	}
+
+	if (mode < 0)
+		return mode;
+
+	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 len;
+}
+
 static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(vf610_show_samp_freq_avail);
 
+static IIO_CONST_ATTR_NAMED(conversion_mode_available,
+	conversion_mode_available, "normal high-speed low-power");
+
+IIO_DEVICE_ATTR(conversion_mode, S_IWUSR | S_IRUGO, vf610_read_mode,
+	vf610_write_mode, 0);
+
 static struct attribute *vf610_attributes[] = {
 	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
+	&iio_const_attr_conversion_mode_available.dev_attr.attr,
+	&iio_dev_attr_conversion_mode.dev_attr.attr,
 	NULL
 };
 
@@ -654,6 +731,9 @@ 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);
-- 
2.2.2

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

[Jonathan Cameron]

On 20/01/15 16:02, Stefan Agner wrote:
> Support configureable 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 calcaulated
> dynamically.
> 
> Signed-off-by: Stefan Agner <stefan@agner.ch>
We have the extinfo stuff to cut down on the boiler plate, particularly
with enum type items like this.  See the various IIO_ENUM() etc in iio.h
> ---
>  drivers/iio/adc/vf610_adc.c | 92 ++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 86 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
> index e63b8e7..fd41d91c 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];
> @@ -146,6 +154,8 @@ struct vf610_adc {
>  	struct completion completion;
>  };
>  
> +static const char * const vf610_conv_modes[] = { "normal", "high-speed",
> +						 "low-power" };
>  static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
>  
>  #define VF610_ADC_CHAN(_idx, _chan_type) {			\
> @@ -186,8 +196,20 @@ static const struct iio_chan_spec vf610_adc_iio_channels[] = {
>  
>  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 +241,8 @@ 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 +327,12 @@ 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);
>  }
> @@ -466,10 +488,65 @@ static ssize_t vf610_show_samp_freq_avail(struct device *dev,
>  	return len;
>  }
>  
> +static ssize_t vf610_read_mode(struct device *dev,
> +		struct device_attribute *attr,
> +		char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct vf610_adc *info = iio_priv(indio_dev);
> +
> +	return sprintf(buf, "%s\n",
> +			vf610_conv_modes[info->adc_feature.conv_mode]);
> +}
> +
> +
> +static ssize_t vf610_write_mode(struct device *dev,
> +		struct device_attribute *attr,
> +		const char *buf,
> +		size_t len)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct vf610_adc *info = iio_priv(indio_dev);
> +	int i, mode = -EINVAL;
> +
> +	mutex_lock(&indio_dev->mlock);
> +	if (iio_buffer_enabled(indio_dev)) {
> +		mutex_unlock(&indio_dev->mlock);
> +		return -EBUSY;
> +	}
> +	mutex_unlock(&indio_dev->mlock);
> +
> +	for (i = 0; i < ARRAY_SIZE(vf610_conv_modes); i++) {
> +		if (!strcmp(vf610_conv_modes[i], buf)) {
> +			mode = i;
> +			break;
> +		}
> +	}
> +
> +	if (mode < 0)
> +		return mode;
> +
> +	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 len;
> +}
> +
>  static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(vf610_show_samp_freq_avail);
>  
> +static IIO_CONST_ATTR_NAMED(conversion_mode_available,
> +	conversion_mode_available, "normal high-speed low-power");
> +
> +IIO_DEVICE_ATTR(conversion_mode, S_IWUSR | S_IRUGO, vf610_read_mode,
> +	vf610_write_mode, 0);
> +
>  static struct attribute *vf610_attributes[] = {
>  	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
> +	&iio_const_attr_conversion_mode_available.dev_attr.attr,
> +	&iio_dev_attr_conversion_mode.dev_attr.attr,
>  	NULL
>  };
>  
> @@ -654,6 +731,9 @@ 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);
> 

[PATCH 3/3] ARM: dts: add property for maximum ADC clock frequencies

[Stefan Agner]

The ADC clock frequency is limited depending on modes used. Add
device tree property which allow to set the mode used and the
maximum frequency ratings for the instance. These allows to
set the ADC clock to a frequency which is within specification
according to the actual mode used.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 Documentation/devicetree/bindings/iio/adc/vf610-adc.txt | 9 +++++++++
 arch/arm/boot/dts/vfxxx.dtsi                            | 4 ++++
 2 files changed, 13 insertions(+)

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/arch/arm/boot/dts/vfxxx.dtsi b/arch/arm/boot/dts/vfxxx.dtsi
index 505969a..7584e0a 100644
--- a/arch/arm/boot/dts/vfxxx.dtsi
+++ b/arch/arm/boot/dts/vfxxx.dtsi
@@ -182,6 +182,8 @@
 				clocks = <&clks VF610_CLK_ADC0>;
 				clock-names = "adc";
 				status = "disabled";
+				fsl,adck-max-frequency = <30000000>, <40000000>,
+							<20000000>;
 			};
 
 			wdog at 4003e000 {
@@ -361,6 +363,8 @@
 				clocks = <&clks VF610_CLK_ADC1>;
 				clock-names = "adc";
 				status = "disabled";
+				fsl,adck-max-frequency = <30000000>, <40000000>,
+							<20000000>;
 			};
 
 			esdhc1: esdhc at 400b2000 {
-- 
2.2.2

[PATCH 3/3] ARM: dts: add property for maximum ADC clock frequencies

[Jonathan Cameron]

On 20/01/15 16:02, Stefan Agner wrote:
> The ADC clock frequency is limited depending on modes used. Add
> device tree property which allow to set the mode used and the
> maximum frequency ratings for the instance. These allows to
> set the ADC clock to a frequency which is within specification
> according to the actual mode used.
> 
> Signed-off-by: Stefan Agner <stefan@agner.ch>
This should have been sent to the devicetree list and maintainers
in the first place.  Now cc'd.
> ---
>  Documentation/devicetree/bindings/iio/adc/vf610-adc.txt | 9 +++++++++
>  arch/arm/boot/dts/vfxxx.dtsi                            | 4 ++++
>  2 files changed, 13 insertions(+)
> 
> 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/arch/arm/boot/dts/vfxxx.dtsi b/arch/arm/boot/dts/vfxxx.dtsi
> index 505969a..7584e0a 100644
> --- a/arch/arm/boot/dts/vfxxx.dtsi
> +++ b/arch/arm/boot/dts/vfxxx.dtsi
> @@ -182,6 +182,8 @@
>  				clocks = <&clks VF610_CLK_ADC0>;
>  				clock-names = "adc";
>  				status = "disabled";
> +				fsl,adck-max-frequency = <30000000>, <40000000>,
> +							<20000000>;
>  			};
>  
>  			wdog at 4003e000 {
> @@ -361,6 +363,8 @@
>  				clocks = <&clks VF610_CLK_ADC1>;
>  				clock-names = "adc";
>  				status = "disabled";
> +				fsl,adck-max-frequency = <30000000>, <40000000>,
> +							<20000000>;
>  			};
>  
>  			esdhc1: esdhc at 400b2000 {
> 

[PATCH 0/3] iio: adc: vf610: respect ADC clocking limitations

[fugang.duan at freescale.com]

From: Stefan Agner <stefan@agner.ch> Sent: Wednesday, January 21, 2015 12:02 AM
> To: jic23 at kernel.org
> Cc: shawn.guo at linaro.org; Duan Fugang-B38611; maitysanchayan at gmail.com;
> linux-iio at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org; stefan at agner.ch
> Subject: [PATCH 0/3] iio: adc: vf610: respect ADC clocking limitations
> 
> Respect ADC clocking limitations which lead to bogous reading on 500MHz
> clocked Vybrid SoC's. Additionally, also implement a sysfs-property to
> configure the conversion mode available in this ADC peripherial.
> 
> Stefan Agner (3):
>   iio: adc: vf610: use ADC clock within specification
>   iio: adc: vf610: implement configurable conversion modes
>   ARM: dts: add property for maximum ADC clock frequencies
> 
>  .../devicetree/bindings/iio/adc/vf610-adc.txt      |   9 ++
>  arch/arm/boot/dts/vfxxx.dtsi                       |   4 +
>  drivers/iio/adc/vf610_adc.c                        | 175
> +++++++++++++++++----
>  3 files changed, 156 insertions(+), 32 deletions(-)
> 
> --
> 2.2.2

The patch set are fine for me.

Acked-by: Fugang Duan <B38611@freescale.com>

Thanks. 
Fugang