linux-kernel - [PATCH v2 10/10] iio: adc: ad7606: Disable PWM usage for non backend version

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Message-Id: <20240920-ad7606_add_iio_backend_support-v2-10-0e78782ae7d0@baylibre.com>
Date: Fri, 20 Sep 2024 17:33:30 +0000
From: Guillaume Stols <gstols@...libre.com>
To: Uwe Kleine-König <ukleinek@...nel.org>, 
 Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, Jonathan Corbet <corbet@....net>, 
 Michal Marek <mmarek@...e.com>
Cc: linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Michael Hennerich <michael.hennerich@...log.com>, 
 linux-fbdev@...r.kernel.org, linux-iio@...r.kernel.org, 
 devicetree@...r.kernel.org, linux-doc@...r.kernel.org, 
 aardelean@...libre.com, dlechner@...libre.com, 
 Guillaume Stols <gstols@...libre.com>, jstephan@...libre.com
Subject: [PATCH v2 10/10] iio: adc: ad7606: Disable PWM usage for non
 backend version

Since the pwm was introduced before backend, there was an example use
whit triggered buffers. However, using it may be dangerous, because if
the PWM goes too fast, a new conversion can be triggered before the
transmission is over, whit the associated mess in the buffers.
Until a solution is found to mitigate this risk, for instante CRC
support, the PWM will be disabled.

Signed-off-by: Guillaume Stols <gstols@...libre.com>
---
 drivers/iio/adc/ad7606.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/ad7606.c b/drivers/iio/adc/ad7606.c
index f710445bdc22..0c12ca237ee9 100644
--- a/drivers/iio/adc/ad7606.c
+++ b/drivers/iio/adc/ad7606.c
@@ -599,7 +599,6 @@ static int ad7606_buffer_postenable(struct iio_dev *indio_dev)
 	struct ad7606_state *st = iio_priv(indio_dev);

 	gpiod_set_value(st->gpio_convst, 1);
-	ad7606_pwm_set_swing(st);

 	return 0;
 }
@@ -609,7 +608,6 @@ static int ad7606_buffer_predisable(struct iio_dev *indio_dev)
 	struct ad7606_state *st = iio_priv(indio_dev);

 	gpiod_set_value(st->gpio_convst, 0);
-	ad7606_pwm_set_low(st);

 	return 0;
 }
@@ -838,6 +836,12 @@ int ad7606_probe(struct device *dev, int irq, void __iomem *base_address,
 		indio_dev->setup_ops = &ad7606_pwm_buffer_ops;
 	} else {
 		init_completion(&st->completion);
+
+		/* Reserve the PWM use only for backend (force gpio_convst definition) */
+		if (!st->gpio_convst)
+			return dev_err_probe(dev, -EINVAL,
+					     "No backend, connect convst to a GPIO");
+
 		ret = devm_request_threaded_irq(dev, irq,
 						NULL,
 						&ad7606_interrupt,

-- 
2.34.1