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

From: maitysanchayan
Date: Mon Aug 10 2015 - 02:38:34 EST

Hello,

On 15-08-08 19:46:00, Jonathan Cameron wrote:
> On 08/08/15 18:22, maitysanchayan@xxxxxxxxx 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 <maitysanchayan@xxxxxxxxx>
> >>> ---
> >>> 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.

Ok.

> >
> > 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.

Alright. Will drop that iio sysfs tigger select from the Kconfig.

>
> 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.

Ok. Will implement the same with a follow up second patch in the third
revision.

- Sanchayan.

> >
> >>> - 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
> >
>
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