Subject: [PATCH v2] iio: adc: vf610: Add IIO buffer support for Vybrid ADC

From: [email-masked] (Jonathan Cameron)
Date: Sat, 8 Aug 2015 15:29:47 +0100

On 05/08/15 13:10, Sanchayan Maity wrote:
> This patch adds support for IIO buffer to the Vybrid ADC driver.
> IIO triggered buffer infrastructure along with iio sysfs trigger
> is used to leverage continuous sampling support provided by the
> ADC block.
Looking good.  Just a couple more bits and pieces inline from me.
One or two of which aren't corrected from Peter's review of v1.

I will want Fugang Dong's ack / review tag on the final version
before applying it however.  This driver is some distance form my
area of expertise!

Jonathan
> 
> Signed-off-by: Sanchayan Maity <[email-masked]>
> ---
>  drivers/iio/adc/Kconfig     |   4 ++
>  drivers/iio/adc/vf610_adc.c | 107 +++++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 105 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 7c55658..4661241 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -337,6 +337,10 @@ config TWL6030_GPADC
>  config VF610_ADC
>  	tristate "Freescale vf610 ADC driver"
>  	depends on OF
> +	select IIO_BUFFER
> +	select IIO_TRIGGER
> +	select IIO_SYSFS_TRIGGER
Unless I missed something there is no dependency on this particular
trigger (it just happens to be the one you've been testing with I guess).
Could be driven from a hardware trigger belonging to another device for
example.

> +	select IIO_TRIGGERED_BUFFER
>  	help
>  	  Say yes here to support for Vybrid board analog-to-digital converter.
>  	  Since the IP is used for i.MX6SLX, the driver also support i.MX6SLX.
> diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c
> index 23b8fb9..97cb2ed 100644
> --- a/drivers/iio/adc/vf610_adc.c
> +++ b/drivers/iio/adc/vf610_adc.c
> @@ -34,8 +34,11 @@
>  #include <linux/err.h>
>  
>  #include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
>  #include <linux/iio/sysfs.h>
> -#include <linux/iio/driver.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
>  
>  /* This will be the driver name the kernel reports */
>  #define DRIVER_NAME "vf610-adc"
> @@ -170,6 +173,7 @@ struct vf610_adc {
>  	u32 sample_freq_avail[5];
>  
>  	struct completion completion;
> +	u16 buffer[2];
Note the requirements on the buffer provided to
iio_push_to_buffers_with_timestamp
Needs to be u16 buffer[8] to allow for the aligned 64bit (4 word) timestamp.

Peter pointed this out in his follow up email and you said you'd implement
it.. Guessing this got lost somewhere.

>  };
>  
>  static const u32 vf610_hw_avgs[] = { 1, 4, 8, 16, 32 };
> @@ -505,12 +509,22 @@ static const struct iio_chan_spec_ext_info vf610_ext_info[] = {
>  	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |	\
>  				BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
>  	.ext_info = vf610_ext_info,				\
> +	.address = (_idx),				\
> +	.scan_index = (_idx),			\
> +	.scan_type.sign = 'u',			\
> +	.scan_type.realbits = 12,		\
> +	.scan_type.storagebits = 16,	\
>  }
>  
>  #define VF610_ADC_TEMPERATURE_CHAN(_idx, _chan_type) {	\
>  	.type = (_chan_type),	\
>  	.channel = (_idx),		\
>  	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),	\
> +	.address = (_idx),						\
> +	.scan_index = (_idx),					\
.scan_type = {
	   .sign = 'u',
	   etc.

Peter picked up on this..

> +	.scan_type.sign = 'u',					\
> +	.scan_type.realbits = 12,				\
> +	.scan_type.storagebits = 16,			\
>  }
>  
>  static const struct iio_chan_spec vf610_adc_iio_channels[] = {
> @@ -531,6 +545,7 @@ static const struct iio_chan_spec vf610_adc_iio_channels[] = {
>  	VF610_ADC_CHAN(14, IIO_VOLTAGE),
>  	VF610_ADC_CHAN(15, IIO_VOLTAGE),
>  	VF610_ADC_TEMPERATURE_CHAN(26, IIO_TEMP),
> +	IIO_CHAN_SOFT_TIMESTAMP(32),
It's bit extreme throwing it out at scan_index 32.  Is there a reason
to think that migh be neccesary?  Mind you, why is the temperature
channel down at 26?  Are we dealing with a set of reserved real channels
inbetween?
>  	/* sentinel */
>  };
>  
> @@ -559,13 +574,20 @@ static int vf610_adc_read_data(struct vf610_adc *info)
>  
>  static irqreturn_t vf610_adc_isr(int irq, void *dev_id)
>  {
> -	struct vf610_adc *info = (struct vf610_adc *)dev_id;
> +	struct iio_dev *indio_dev = (struct iio_dev *)dev_id;
> +	struct vf610_adc *info = iio_priv(indio_dev);
>  	int coco;
>  
>  	coco = readl(info->regs + VF610_REG_ADC_HS);
>  	if (coco & VF610_ADC_HS_COCO0) {
>  		info->value = vf610_adc_read_data(info);

I'd be tempted to make the non buffered path also use
info->bufffer[0] and drop info->value entirely.
A more invasive patch, but a cleaner resulting code (slightly!)
> -		complete(&info->completion);
> +		if (iio_buffer_enabled(indio_dev)) {
> +			info->buffer[0] = info->value;
> +			iio_push_to_buffers_with_timestamp(indio_dev,
> +					info->buffer, iio_get_time_ns());
> +			iio_trigger_notify_done(indio_dev->trig);
> +		} else
> +			complete(&info->completion);
>  	}
>  
>  	return IRQ_HANDLED;
> @@ -612,6 +634,9 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
>  	case IIO_CHAN_INFO_PROCESSED:

To avoid possible races this check should be done under the mlock.
> +		if (iio_buffer_enabled(indio_dev))
> +			return -EBUSY;
> +
>  		mutex_lock(&indio_dev->mlock);
>  		reinit_completion(&info->completion);
>  
> @@ -694,6 +719,68 @@ static int vf610_write_raw(struct iio_dev *indio_dev,
>  	return -EINVAL;
>  }
>  
> +static int vf610_adc_buffer_postenable(struct iio_dev *indio_dev)
> +{
> +	struct vf610_adc *info = iio_priv(indio_dev);
> +	unsigned int channel;
> +	int ret;
> +	int val;
> +
> +	ret = iio_triggered_buffer_postenable(indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	val = readl(info->regs + VF610_REG_ADC_GC);
> +	val |= VF610_ADC_ADCON;
> +	writel(val, info->regs + VF610_REG_ADC_GC);
> +
> +	channel = find_first_bit(indio_dev->active_scan_mask,
> +						indio_dev->masklength);
> +
> +	val = VF610_ADC_ADCHC(channel);
> +	val |= VF610_ADC_AIEN;
> +
> +	writel(val, info->regs + VF610_REG_ADC_HC0);
> +
> +	return 0;
> +}
> +
> +static int vf610_adc_buffer_postdisable(struct iio_dev *indio_dev)
> +{
> +	struct vf610_adc *info = iio_priv(indio_dev);
> +	unsigned int hc_cfg = 0;
> +	int val;
> +
> +	val = readl(info->regs + VF610_REG_ADC_GC);
> +	val &= ~VF610_ADC_ADCON;
> +	writel(val, info->regs + VF610_REG_ADC_GC);
> +
> +	hc_cfg |= VF610_ADC_CONV_DISABLE;
> +	hc_cfg &= ~VF610_ADC_AIEN;
> +
> +	writel(hc_cfg, info->regs + VF610_REG_ADC_HC0);
> +
> +	return 0;
> +}
> +
> +static const struct iio_buffer_setup_ops iio_triggered_buffer_setup_ops = {
> +	.postenable = &vf610_adc_buffer_postenable,
> +	.predisable = &iio_triggered_buffer_predisable,
> +	.postdisable = &vf610_adc_buffer_postdisable,
> +	.validate_scan_mask = &iio_validate_scan_mask_onehot,
> +};
> +
> +static int vf610_adc_buffer_init(struct iio_dev *indio_dev)
> +{
> +	return iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
> +		NULL, &iio_triggered_buffer_setup_ops);
> +}
> +
> +static void vf610_adc_buffer_remove(struct iio_dev *indio_dev)
> +{
> +	iio_triggered_buffer_cleanup(indio_dev);
> +}
These to wrappers seem a little superflous. I'd have just put the code
inline, but it's obviously a matter of personal taste and I don't care
that much!

> +
>  static int vf610_adc_reg_access(struct iio_dev *indio_dev,
>  			unsigned reg, unsigned writeval,
>  			unsigned *readval)
> @@ -753,7 +840,7 @@ static int vf610_adc_probe(struct platform_device *pdev)
>  
>  	ret = devm_request_irq(info->dev, irq,
>  				vf610_adc_isr, 0,
> -				dev_name(&pdev->dev), info);
> +				dev_name(&pdev->dev), indio_dev);
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "failed requesting irq, irq = %d\n", irq);
>  		return ret;
> @@ -806,15 +893,22 @@ static int vf610_adc_probe(struct platform_device *pdev)
>  	vf610_adc_cfg_init(info);
>  	vf610_adc_hw_init(info);
>  
> +	ret = vf610_adc_buffer_init(indio_dev);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "Couldn't initialise the buffer\n");
> +		goto error_iio_device_register;
> +	}
> +
>  	ret = iio_device_register(indio_dev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Couldn't register the device.\n");
> -		goto error_iio_device_register;
> +		goto error_adc_buffer_init;
>  	}
>  
>  	return 0;
>  
> -
> +error_adc_buffer_init:
> +	vf610_adc_buffer_remove(indio_dev);
>  error_iio_device_register:
>  	clk_disable_unprepare(info->clk);
>  error_adc_clk_enable:
> @@ -829,6 +923,7 @@ static int vf610_adc_remove(struct platform_device *pdev)
>  	struct vf610_adc *info = iio_priv(indio_dev);
>  
>  	iio_device_unregister(indio_dev);
> +	vf610_adc_buffer_remove(indio_dev);
>  	regulator_disable(info->vref);
>  	clk_disable_unprepare(info->clk);
>  
>