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

From: [email-masked] (Jonathan Cameron)
Date: Sat, 8 Aug 2015 19:46:00 +0100

On 08/08/15 18:22, maitysanchayan at gmail.com wrote:
> Hello Jonathan,
> 
> On 15-08-08 15:29:47, Jonathan Cameron wrote:
>> 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.
> 
> Sure.
> 
>> This driver is some distance form my area of expertise!
> 
> I doubt :).
> 
>>
>> 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.
> 
> Yes right in a way. Right now we do not provide or there is no provision
> for hardware triggers. On the Vybrid, the Peripheral Delay Block (PDB)
> does the job of providing support for software and hardware triggers. PDB
> support is not yet there in Linux however. 
Not supplying a trigger is fine, but any trigger (that allows other devices
to bind to it) will be fine.
> 
> There is also the question of where the Vybrid PDB driver would belong
> to? In the TRM it is put in the timers but the kernel has no generic timer
> framework that I am aware of.
It's been debated a number of times, but no one has ever written one.
Not seen anything recently on this topic..  Lars, you seen anything?
(the blackfin-timer trigger is similar to what you are describing I think).

> After some internal reviews we decided to
> do a platform driver which provided functions ADC driver could called into.
Does rather feel like there ought to be at least a standard home for these.
Might be worth asking the arm-soc guys...
> 
> I have a patchset ready which provides trigger support using PDB however
> configuring the PDB properly has proven to be tricky. While it works but
> not reliably with multiple channels and it would be a while before I get
> that working and post that patchset. So kind of stalled there and just
> because of two registers which need to be written with the correct value
> :). For what it's worth if someone comes across this, some discussion
> here [1] along with patches. (Note however those are a bit old patches
> not exactly my new work).
> 
> Sorry for digressing from the topic. Anyways so the idea was to provide
> sysfs triggers as default for using this continuous sampling. Later the
> driver may provide additional triggers. So for now I added the sysfs
> trigger as a select option so that a user won't have to recompile the
> kernel for using the buffers with continuous sampling.
It's a policy decision so should really be left to the distro builders.
There are lots of possible triggers out there (though sysfs might be
the most likely one!)

Hence don't put the select there in Kconfig.  We should shortly have
Daniel's update to the patches for the high resolution timer
which would give another obvious choice for starters.

I doubt many distros build without the sysfs triggers but with other IIO
stuff.

> 
>>
>>> +	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.
> 
> No, I meant to implement what Peter recommended but I guess I did not completely
> grasp what he intended. Sorry about that. Will fix this and ask further if in
> more doubts.
> 
>>
>>
>>>  };
>>>  
>>>  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..
> 
> Sorry yes missed that. Will definitely fix.
> 
>>
>>> +	.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?
> 
> 
> The temperature channel is the 26th channel and there are some reserved
> channels in between. 31st is the channel which acts as a conversion
> disabled setting. So I put the timestamp at index 32.
Fair enough if weird ;)
> 
> 
>>>  	/* 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!)
> 
> I did think of that but decided against it as I wanted the changes
> to as less invasive as possible making only the necessary changes
> and keeping the old code as is.
You could do this then clean up in a follow up patch which would be
really easy to review.
> 
>>> -		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
> 
> Thanks for picking this. Somehow I remember seeing it outside of the
> mlock. However grepping again shows otherwise. Will fix.
> 
> .
>>> +		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!
> 
> Ok. I do not have strong opinions on this. I just tried to follow how the
> at91 adc code did it considering it as a good example. Will drop it.
> 
>>
>>> +
>>>  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);
>>>  
>>>
>>
> 
> Thanks for the review.
> 
> - Sanchayan.
> 
> [1]. https://community.freescale.com/thread/357619
>