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From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Nuno Sa <Nuno.Sa@analog.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>
Subject: [PATCH v4 14/16] iio: adc: max1027: Use the EOC IRQ when populated for single reads
Date: Tue, 21 Sep 2021 13:54:06 +0200	[thread overview]
Message-ID: <20210921115408.66711-15-miquel.raynal@bootlin.com> (raw)
In-Reply-To: <20210921115408.66711-1-miquel.raynal@bootlin.com>

So far the End-Of-Conversion interrupt was only used in conjunction with
the internal trigger to process the data. Let's extend the use of this
interrupt handler to support regular single-shot conversions as well.

Doing so requires writing our own hard IRQ handler. This handler has to
check if buffers are enabled or not:

*** Buffers disabled condition ***

  This means the user requested a single conversion and the sample is
  ready to be retrieved.

    -> This implies adding the relevant completion boilerplate.

*** Buffers enabled condition ***

  Triggers are used. So far there is only support for the internal
  trigger but this trigger might soon be attached to another device as
  well so it is the core duty to decide which handler to call in order
  to process the data. The core will decide to either:

  * Call the internal trigger handler which will extract the data that
    is already present in the ADC FIFOs

  or

  * Call the trigger handler of another driver when using this trigger
    with another device, even though this call will be slightly delayed
    by the fact that the max1027 IRQ is a data-ready interrupt rather
    than a real trigger:

  -> The new handler will manually inform the core about the trigger
     having transitioned by directly calling iio_trigger_poll() (which
     iio_trigger_generic_data_rdy_poll() initially did).

In order for the handler to be "source" agnostic, we also need to change
the private pointer and provide the IIO device instead of the trigger
object.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---

Jonathan,

I hope this fits the IIO model now. In order to be sure I got the big
picture I first refused to look at your code snippets. Just with your
"plain english" explanations I wrote most of these three patches, before
checking back that they were indeed fully aligned with your examples. I
truly hope they do now, but do not hesitate if I missed something.

Cheers,
Miquèl

 drivers/iio/adc/max1027.c | 43 +++++++++++++++++++++++++++++++++++----
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
index 84217e18ef70..0fa7b0fbdba0 100644
--- a/drivers/iio/adc/max1027.c
+++ b/drivers/iio/adc/max1027.c
@@ -270,15 +270,26 @@ struct max1027_state {
 	struct iio_trigger		*trig;
 	__be16				*buffer;
 	struct mutex			lock;
+	struct completion		complete;
 
 	u8				reg ____cacheline_aligned;
 };
 
 static int max1027_wait_eoc(struct iio_dev *indio_dev)
 {
+	struct max1027_state *st = iio_priv(indio_dev);
 	unsigned int conversion_time = MAX1027_CONVERSION_UDELAY;
+	int ret;
 
-	usleep_range(conversion_time, conversion_time * 2);
+	if (st->spi->irq) {
+		ret = wait_for_completion_timeout(&st->complete,
+						  msecs_to_jiffies(1000));
+		reinit_completion(&st->complete);
+		if (!ret)
+			return ret;
+	} else {
+		usleep_range(conversion_time, conversion_time * 2);
+	}
 
 	return 0;
 }
@@ -473,6 +484,30 @@ static int max1027_read_scan(struct iio_dev *indio_dev)
 	return 0;
 }
 
+static irqreturn_t max1027_handler(int irq, void *private)
+{
+	struct iio_dev *indio_dev = private;
+	struct max1027_state *st = iio_priv(indio_dev);
+
+	/*
+	 * If buffers are disabled (raw read), we just need to unlock the
+	 * waiters which will then handle the data.
+	 *
+	 * When using the internal trigger, we must hand-off the choice of the
+	 * handler to the core which will then lookup through the interrupt tree
+	 * for the right handler registered with iio_triggered_buffer_setup()
+	 * to execute, as this trigger might very well be used in conjunction
+	 * with another device. The core will then call the relevant handler to
+	 * perform the data processing step.
+	 */
+	if (!iio_buffer_enabled(indio_dev))
+		complete(&st->complete);
+	else
+		iio_trigger_poll(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
 static irqreturn_t max1027_trigger_handler(int irq, void *private)
 {
 	struct iio_poll_func *pf = private;
@@ -517,6 +552,7 @@ static int max1027_probe(struct spi_device *spi)
 	st->info = &max1027_chip_info_tbl[spi_get_device_id(spi)->driver_data];
 
 	mutex_init(&st->lock);
+	init_completion(&st->complete);
 
 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->info = &max1027_info;
@@ -560,10 +596,9 @@ static int max1027_probe(struct spi_device *spi)
 			return ret;
 		}
 
-		ret = devm_request_irq(&spi->dev, spi->irq,
-				       iio_trigger_generic_data_rdy_poll,
+		ret = devm_request_irq(&spi->dev, spi->irq, max1027_handler,
 				       IRQF_TRIGGER_FALLING,
-				       spi->dev.driver->name, st->trig);
+				       spi->dev.driver->name, indio_dev);
 		if (ret < 0) {
 			dev_err(&indio_dev->dev, "Failed to allocate IRQ.\n");
 			return ret;
-- 
2.27.0


  parent reply	other threads:[~2021-09-21 11:54 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-21 11:53 [PATCH v4 00/16] Bring external triggers support to MAX1027-like ADCs Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 01/16] iio: adc: max1027: Fix style Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 02/16] iio: adc: max1027: Drop extra warning message Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 03/16] iio: adc: max1027: Drop useless debug messages Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 04/16] iio: adc: max1027: Minimize the number of converted channels Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 05/16] iio: adc: max1027: Rename a helper Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 06/16] iio: adc: max1027: Create a helper to enable/disable the cnvst trigger Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 07/16] iio: adc: max1027: Simplify the _set_trigger_state() helper Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 08/16] iio: adc: max1027: Ensure a default cnvst trigger configuration Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 09/16] iio: adc: max1027: Create a helper to configure the channels to scan Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 10/16] iio: adc: max1027: Prevent single channel accesses during buffer reads Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 11/16] iio: adc: max1027: Separate the IRQ handler from the read logic Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 12/16] iio: adc: max1027: Introduce an end of conversion helper Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 13/16] iio: adc: max1027: Stop requesting a threaded IRQ Miquel Raynal
2021-09-21 11:54 ` Miquel Raynal [this message]
2021-09-26 14:36   ` [PATCH v4 14/16] iio: adc: max1027: Use the EOC IRQ when populated for single reads Jonathan Cameron
2021-09-27 14:30     ` Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 15/16] iio: adc: max1027: Allow all kind of triggers to be used Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 16/16] iio: adc: max1027: Don't reject external triggers when there is no IRQ Miquel Raynal
2021-09-26 14:38 ` [PATCH v4 00/16] Bring external triggers support to MAX1027-like ADCs Jonathan Cameron

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