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Message-ID: <20181216134913.1751b640@archlinux>
Date: Sun, 16 Dec 2018 13:49:13 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Stefan Popa <stefan.popa@...log.com>
Cc: <robh+dt@...nel.org>, <mark.rutland@....com>,
<Michael.Hennerich@...log.com>, <knaack.h@....de>,
<lars@...afoo.de>, <pmeerw@...erw.net>,
<gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>,
<linux-iio@...r.kernel.org>, <devel@...verdev.osuosl.org>,
<stefan.popa@...log.co>
Subject: Re: [PATCH 05/11] staging: iio: adc: ad7606: Add support for
threaded irq
On Thu, 13 Dec 2018 14:46:17 +0200
Stefan Popa <stefan.popa@...log.com> wrote:
> This patch replaces the use of a polling ring buffer with a threaded
> interrupt.
>
> Enabling the buffer sets the CONVST signal to high. When the rising edge
> of the CONVST is applied, BUSY signal goes logic high and transitions low
> at the end of the entire conversion process. The falling edge of the BUSY
> signal triggers the interrupt.
>
> ad7606_trigger_handler() is used as bottom half of the poll function.
> It reads data from the device and stores it in the internal buffer.
>
> Signed-off-by: Stefan Popa <stefan.popa@...log.com>
I'd like a little more info as comments in this one. See below.
Which is another way of saying I have no idea what is going on :)
Thanks,
Jonathan.
> ---
> drivers/staging/iio/adc/ad7606.c | 116 +++++++++++++++++++++++++++++----------
> drivers/staging/iio/adc/ad7606.h | 6 +-
> 2 files changed, 89 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/staging/iio/adc/ad7606.c b/drivers/staging/iio/adc/ad7606.c
> index 7191d51..13aeeec 100644
> --- a/drivers/staging/iio/adc/ad7606.c
> +++ b/drivers/staging/iio/adc/ad7606.c
> @@ -21,6 +21,7 @@
> #include <linux/iio/sysfs.h>
> #include <linux/iio/buffer.h>
> #include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/trigger.h>
> #include <linux/iio/triggered_buffer.h>
>
> #include "ad7606.h"
> @@ -81,36 +82,24 @@ static int ad7606_read_samples(struct ad7606_state *st)
> static irqreturn_t ad7606_trigger_handler(int irq, void *p)
> {
> struct iio_poll_func *pf = p;
> - struct ad7606_state *st = iio_priv(pf->indio_dev);
> -
> - gpiod_set_value(st->gpio_convst, 1);
> -
> - return IRQ_HANDLED;
> -}
> -
> -/**
> - * ad7606_poll_bh_to_ring() bh of trigger launched polling to ring buffer
> - * @work_s: the work struct through which this was scheduled
> - *
> - * Currently there is no option in this driver to disable the saving of
> - * timestamps within the ring.
> - * I think the one copy of this at a time was to avoid problems if the
> - * trigger was set far too high and the reads then locked up the computer.
> - **/
> -static void ad7606_poll_bh_to_ring(struct work_struct *work_s)
> -{
> - struct ad7606_state *st = container_of(work_s, struct ad7606_state,
> - poll_work);
> - struct iio_dev *indio_dev = iio_priv_to_dev(st);
> + struct iio_dev *indio_dev = pf->indio_dev;
> + struct ad7606_state *st = iio_priv(indio_dev);
> int ret;
>
> + mutex_lock(&st->lock);
> +
> ret = ad7606_read_samples(st);
> if (ret == 0)
> iio_push_to_buffers_with_timestamp(indio_dev, st->data,
> iio_get_time_ns(indio_dev));
>
> - gpiod_set_value(st->gpio_convst, 0);
> iio_trigger_notify_done(indio_dev->trig);
> + /* The rising edge of the CONVST signal starts a new conversion. */
> + gpiod_set_value(st->gpio_convst, 1);
> +
> + mutex_unlock(&st->lock);
> +
> + return IRQ_HANDLED;
> }
>
> static int ad7606_scan_direct(struct iio_dev *indio_dev, unsigned int ch)
> @@ -378,8 +367,11 @@ static int ad7606_request_gpios(struct ad7606_state *st)
> return PTR_ERR_OR_ZERO(st->gpio_os);
> }
>
> -/**
> - * Interrupt handler
> +/*
> + * The BUSY signal indicates when conversions are in progress, so when a rising
> + * edge of CONVST is applied, BUSY goes logic high and transitions low at the
> + * end of the entire conversion process. The falling edge of the BUSY signal
> + * triggers this interrupt.
> */
> static irqreturn_t ad7606_interrupt(int irq, void *dev_id)
> {
> @@ -387,7 +379,8 @@ static irqreturn_t ad7606_interrupt(int irq, void *dev_id)
> struct ad7606_state *st = iio_priv(indio_dev);
>
> if (iio_buffer_enabled(indio_dev)) {
> - schedule_work(&st->poll_work);
> + gpiod_set_value(st->gpio_convst, 0);
> + iio_trigger_poll_chained(st->trig);
> } else {
> complete(&st->completion);
> }
> @@ -395,26 +388,74 @@ static irqreturn_t ad7606_interrupt(int irq, void *dev_id)
> return IRQ_HANDLED;
> };
>
> +static int ad7606_validate_trigger(struct iio_dev *indio_dev,
> + struct iio_trigger *trig)
> +{
> + struct ad7606_state *st = iio_priv(indio_dev);
> +
> + if (st->trig != trig)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static int ad7606_buffer_postenable(struct iio_dev *indio_dev)
> +{
> + struct ad7606_state *st = iio_priv(indio_dev);
> +
> + iio_triggered_buffer_postenable(indio_dev);
> + gpiod_set_value(st->gpio_convst, 1);
> +
> + return 0;
> +}
> +
> +static int ad7606_buffer_predisable(struct iio_dev *indio_dev)
> +{
> + struct ad7606_state *st = iio_priv(indio_dev);
> + int ret;
> +
> + reinit_completion(&st->completion);
> + gpiod_set_value(st->gpio_convst, 1);
> + ret = wait_for_completion_timeout(&st->completion,
> + msecs_to_jiffies(1000));
Along with Dan's comment. I'd like to see a comment here on what
is actually going on. Not immediately obvious a conversion should
be triggered to disable the buffer...
I'll guess there is a race against the normal handler that we
are closing with this dance, but that race needs explaining.
> + gpiod_set_value(st->gpio_convst, 0);
> +
> + return iio_triggered_buffer_predisable(indio_dev);
> +}
> +
> +static const struct iio_buffer_setup_ops ad7606_buffer_ops = {
> + .postenable = &ad7606_buffer_postenable,
> + .predisable = &ad7606_buffer_predisable,
> +};
> +
> static const struct iio_info ad7606_info_no_os_or_range = {
> .read_raw = &ad7606_read_raw,
> + .validate_trigger = &ad7606_validate_trigger,
> };
>
> static const struct iio_info ad7606_info_os_and_range = {
> .read_raw = &ad7606_read_raw,
> .write_raw = &ad7606_write_raw,
> .attrs = &ad7606_attribute_group_os_and_range,
> + .validate_trigger = &ad7606_validate_trigger,
> };
>
> static const struct iio_info ad7606_info_os = {
> .read_raw = &ad7606_read_raw,
> .write_raw = &ad7606_write_raw,
> .attrs = &ad7606_attribute_group_os,
> + .validate_trigger = &ad7606_validate_trigger,
> };
>
> static const struct iio_info ad7606_info_range = {
> .read_raw = &ad7606_read_raw,
> .write_raw = &ad7606_write_raw,
> .attrs = &ad7606_attribute_group_range,
> + .validate_trigger = &ad7606_validate_trigger,
> +};
> +
> +static const struct iio_trigger_ops ad7606_trigger_ops = {
> + .validate_device = iio_trigger_validate_own_device,
> };
>
> static void ad7606_regulator_disable(void *data)
> @@ -446,7 +487,6 @@ int ad7606_probe(struct device *dev, int irq, void __iomem *base_address,
> /* tied to logic low, analog input range is +/- 5V */
> st->range = 0;
> st->oversampling = 1;
> - INIT_WORK(&st->poll_work, &ad7606_poll_bh_to_ring);
>
> st->reg = devm_regulator_get(dev, "avcc");
> if (IS_ERR(st->reg))
> @@ -491,14 +531,32 @@ int ad7606_probe(struct device *dev, int irq, void __iomem *base_address,
> if (ret)
> dev_warn(st->dev, "failed to RESET: no RESET GPIO specified\n");
>
> - ret = devm_request_irq(dev, irq, ad7606_interrupt, IRQF_TRIGGER_FALLING,
> - name, indio_dev);
> + st->trig = devm_iio_trigger_alloc(dev, "%s-dev%d",
> + indio_dev->name, indio_dev->id);
> + if (!st->trig)
> + return -ENOMEM;
> +
> + st->trig->ops = &ad7606_trigger_ops;
> + st->trig->dev.parent = dev;
> + iio_trigger_set_drvdata(st->trig, indio_dev);
> + ret = devm_iio_trigger_register(dev, st->trig);
> + if (ret)
> + return ret;
> +
> + indio_dev->trig = iio_trigger_get(st->trig);
> +
> + ret = devm_request_threaded_irq(dev, irq,
> + NULL,
> + &ad7606_interrupt,
> + IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
> + name, indio_dev);
> if (ret)
> return ret;
>
> ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
> + &iio_pollfunc_store_time,
> &ad7606_trigger_handler,
> - NULL, NULL);
> + &ad7606_buffer_ops);
> if (ret)
> return ret;
>
> diff --git a/drivers/staging/iio/adc/ad7606.h b/drivers/staging/iio/adc/ad7606.h
> index 70486ef..b238e9b 100644
> --- a/drivers/staging/iio/adc/ad7606.h
> +++ b/drivers/staging/iio/adc/ad7606.h
> @@ -26,8 +26,6 @@ struct ad7606_chip_info {
> * @dev pointer to kernel device
> * @chip_info entry in the table of chips that describes this device
> * @reg regulator info for the the power supply of the device
> - * @poll_work work struct for continuously reading data from the device
> - * into an IIO triggered buffer
> * @bops bus operations (SPI or parallel)
> * @range voltage range selection, selects which scale to apply
> * @oversampling oversampling selection
> @@ -42,14 +40,13 @@ struct ad7606_chip_info {
> * is being read on the first channel
> * @gpio_os GPIO descriptors to control oversampling on the device
> * @complete completion to indicate end of conversion
> + * @trig The IIO trigger associated with the device.
> * @data buffer for reading data from the device
> */
> -
> struct ad7606_state {
> struct device *dev;
> const struct ad7606_chip_info *chip_info;
> struct regulator *reg;
> - struct work_struct poll_work;
> const struct ad7606_bus_ops *bops;
> unsigned int range;
> unsigned int oversampling;
> @@ -62,6 +59,7 @@ struct ad7606_state {
> struct gpio_desc *gpio_standby;
> struct gpio_desc *gpio_frstdata;
> struct gpio_descs *gpio_os;
> + struct iio_trigger *trig;
> struct completion completion;
>
> /*
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