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From c979072887ef70aab2ab6e71544853df71017925 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Wed, 12 Jan 2022 08:23:28 +0000
Subject: [PATCH] spi: gpio: Add sck-idle-input property
The sck-idle-input property indicates that the spi-gpio driver should
return the SCK line to an input when the chip select signals are
inactive.
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
drivers/spi/spi-gpio.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -35,6 +35,7 @@ struct spi_gpio {
struct gpio_desc *sck;
struct gpio_desc *miso;
struct gpio_desc *mosi;
+ bool sck_idle_input;
struct gpio_desc **cs_gpios;
};
@@ -201,8 +202,12 @@ static void spi_gpio_chipselect(struct s
struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
/* set initial clock line level */
- if (is_active)
- gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL);
+ if (is_active) {
+ if (spi_gpio->sck_idle_input)
+ gpiod_direction_output(spi_gpio->sck, spi->mode & SPI_CPOL);
+ else
+ gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL);
+ }
/* Drive chip select line, if we have one */
if (spi_gpio->cs_gpios) {
@@ -211,6 +216,9 @@ static void spi_gpio_chipselect(struct s
/* SPI chip selects are normally active-low */
gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
}
+
+ if (spi_gpio->sck_idle_input && !is_active)
+ gpiod_direction_input(spi_gpio->sck);
}
static int spi_gpio_setup(struct spi_device *spi)
@@ -289,6 +297,7 @@ static int spi_gpio_request(struct devic
if (IS_ERR(spi_gpio->miso))
return PTR_ERR(spi_gpio->miso);
+ spi_gpio->sck_idle_input = device_property_read_bool(dev, "sck-idle-input");
spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
return PTR_ERR_OR_ZERO(spi_gpio->sck);
}
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