linux-kernel - [PATCH 4.4 056/190] iio: hi8435: cleanup reset gpio

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Date:   Wed, 11 Apr 2018 20:35:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.4 056/190] iio: hi8435: cleanup reset gpio

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nikita Yushchenko <nikita.yoush@...entembedded.com>


[ Upstream commit 61305664a542f874283f74bf0b27ddb31f5045d7 ]

Reset GPIO is active low.

Currently driver uses gpiod_set_value(1) to clean reset, which depends
on device tree to contain GPIO_ACTIVE_HIGH - that does not match reality.

This fixes driver to use _raw version of gpiod_set_value() to enforce
active-low semantics despite of what's written in device tree. Allowing
device tree to override that only opens possibility for errors and does
not add any value.

Additionally, use _cansleep version to make things work with i2c-gpio
and other sleeping gpio drivers.

Signed-off-by: Nikita Yushchenko <nikita.yoush@...entembedded.com>
Signed-off-by: Jonathan Cameron <jic23@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/iio/adc/hi8435.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/iio/adc/hi8435.c
+++ b/drivers/iio/adc/hi8435.c
@@ -453,13 +453,15 @@ static int hi8435_probe(struct spi_devic
 	priv->spi = spi;
 
 	reset_gpio = devm_gpiod_get(&spi->dev, NULL, GPIOD_OUT_LOW);
-	if (IS_ERR(reset_gpio)) {
-		/* chip s/w reset if h/w reset failed */
+	if (!IS_ERR(reset_gpio)) {
+		/* need >=100ns low pulse to reset chip */
+		gpiod_set_raw_value_cansleep(reset_gpio, 0);
+		udelay(1);
+		gpiod_set_raw_value_cansleep(reset_gpio, 1);
+	} else {
+		/* s/w reset chip if h/w reset is not available */
 		hi8435_writeb(priv, HI8435_CTRL_REG, HI8435_CTRL_SRST);
 		hi8435_writeb(priv, HI8435_CTRL_REG, 0);
-	} else {
-		udelay(5);
-		gpiod_set_value(reset_gpio, 1);
 	}
 
 	spi_set_drvdata(spi, idev);