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Date: Fri, 29 Jan 2016 07:31:37 +0100
From: Sean Nyekjær <sean.nyekjaer@...vas.dk>
To: "Andrew F. Davis" <afd@...com>,
Linus Walleij <linus.walleij@...aro.org>,
Alexandre Courbot <gnurou@...il.com>,
Mark Brown <broonie@...nel.org>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>
CC: <linux-gpio@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] gpio: Add driver for SPI serializers
On 2016-01-25 17:37, Andrew F. Davis wrote:
> Add generic parallel-in/serial-out shift register GPIO driver.
>
> This includes SPI compatible devices like SN74165 serial-out shift
> registers and the SN65HVS88x series of industrial serializers that can
> be read over the SPI bus and used for GPI (General Purpose Input).
>
> Signed-off-by: Andrew F. Davis <afd@...com>
> ---
> drivers/gpio/Kconfig | 6 ++
> drivers/gpio/Makefile | 1 +
> drivers/gpio/gpio-pisosr.c | 188 +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 195 insertions(+)
> create mode 100644 drivers/gpio/gpio-pisosr.c
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index c88dd24..bec3489 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -1011,6 +1011,12 @@ config GPIO_MC33880
> SPI driver for Freescale MC33880 high-side/low-side switch.
> This provides GPIO interface supporting inputs and outputs.
>
> +config GPIO_PISOSR
> + tristate "Generic parallel-in/serial-out shift register"
> + help
> + GPIO driver for SPI compatible parallel-in/serial-out shift
> + registers. These are input only devices.
> +
> endmenu
>
> menu "SPI or I2C GPIO expanders"
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index ece7d7c..8e4f09f 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -75,6 +75,7 @@ obj-$(CONFIG_GPIO_OMAP) += gpio-omap.o
> obj-$(CONFIG_GPIO_PCA953X) += gpio-pca953x.o
> obj-$(CONFIG_GPIO_PCF857X) += gpio-pcf857x.o
> obj-$(CONFIG_GPIO_PCH) += gpio-pch.o
> +obj-$(CONFIG_GPIO_PISOSR) += gpio-pisosr.o
> obj-$(CONFIG_GPIO_PL061) += gpio-pl061.o
> obj-$(CONFIG_GPIO_PXA) += gpio-pxa.o
> obj-$(CONFIG_GPIO_RC5T583) += gpio-rc5t583.o
> diff --git a/drivers/gpio/gpio-pisosr.c b/drivers/gpio/gpio-pisosr.c
> new file mode 100644
> index 0000000..58ea08d
> --- /dev/null
> +++ b/drivers/gpio/gpio-pisosr.c
> @@ -0,0 +1,188 @@
> +/*
> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
> + * Andrew F. Davis <afd@...com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether expressed or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License version 2 for more details.
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/spi/spi.h>
> +
> +#define DEFAULT_NGPIO 8
> +
> +/**
> + * struct pisosr_gpio - GPIO driver data
> + * @chip: GPIO controller chip
> + * @spi: SPI device pointer
> + * @buffer: Buffer for device reads
> + * @buffer_size: Size of buffer
> + * @load_gpio: GPIO pin used to load input into device
> + * @lock: Protects read sequences
> + */
> +struct pisosr_gpio {
> + struct gpio_chip chip;
> + struct spi_device *spi;
> + u8 *buffer;
> + size_t buffer_size;
> + struct gpio_desc *load_gpio;
> + struct mutex lock;
> +};
> +
> +static int pisosr_gpio_refresh(struct pisosr_gpio *gpio)
> +{
> + int ret;
> +
> + mutex_lock(&gpio->lock);
> +
> + if (gpio->load_gpio) {
> + gpiod_set_value(gpio->load_gpio, 1);
> + udelay(1); /* registers load time (~10ns) */
> + gpiod_set_value(gpio->load_gpio, 0);
> + udelay(1); /* registers recovery time (~5ns) */
> + }
> +
> + ret = spi_read(gpio->spi, gpio->buffer, gpio->buffer_size);
> + if (ret)
> + return ret;
> +
> + mutex_unlock(&gpio->lock);
> +
> + return 0;
> +}
> +
> +static int pisosr_gpio_get_direction(struct gpio_chip *chip,
> + unsigned offset)
> +{
> + /* This device always input */
> + return 1;
> +}
> +
> +static int pisosr_gpio_direction_input(struct gpio_chip *chip,
> + unsigned offset)
> +{
> + /* This device always input */
> + return 0;
> +}
> +
> +static int pisosr_gpio_direction_output(struct gpio_chip *chip,
> + unsigned offset, int value)
> +{
> + /* This device is input only */
> + return -EINVAL;
> +}
> +
> +static int pisosr_gpio_get(struct gpio_chip *chip, unsigned offset)
> +{
> + struct pisosr_gpio *gpio = gpiochip_get_data(chip);
> +
> + /* Refresh may not always be needed */
> + pisosr_gpio_refresh(gpio);
> +
> + return (gpio->buffer[offset / 8] >> (offset % 8)) & 0x1;
> +}
> +
> +static struct gpio_chip template_chip = {
> + .label = "pisosr-gpio",
> + .owner = THIS_MODULE,
> + .get_direction = pisosr_gpio_get_direction,
> + .direction_input = pisosr_gpio_direction_input,
> + .direction_output = pisosr_gpio_direction_output,
> + .get = pisosr_gpio_get,
> + .base = -1,
> + .ngpio = DEFAULT_NGPIO,
> + .can_sleep = true,
> +};
> +
> +static int pisosr_gpio_probe(struct spi_device *spi)
> +{
> + struct device *dev = &spi->dev;
> + struct pisosr_gpio *gpio;
> + int ret;
> +
> + gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
> + if (!gpio)
> + return -ENOMEM;
> +
> + spi_set_drvdata(spi, gpio);
> +
> + gpio->chip = template_chip;
> + gpio->chip.parent = dev;
> + of_property_read_u16(dev->of_node, "ngpios", &gpio->chip.ngpio);
> +
> + gpio->spi = spi;
> +
> + gpio->buffer_size = DIV_ROUND_UP(gpio->chip.ngpio, 8);
> + gpio->buffer = devm_kzalloc(dev, gpio->buffer_size, GFP_KERNEL);
> + if (!gpio->buffer)
> + return -ENOMEM;
> +
> + gpio->load_gpio = devm_gpiod_get(dev, "load", GPIOD_OUT_LOW);
> + if (IS_ERR(gpio->load_gpio)) {
> + ret = PTR_ERR(gpio->load_gpio);
> + if (ret != -ENOENT && ret != -ENOSYS) {
> + if (ret != -EPROBE_DEFER)
> + dev_err(dev, "Unable to allocate load GPIO\n");
> + return ret;
> + }
> + gpio->load_gpio = NULL;
> + }
> +
> + mutex_init(&gpio->lock);
> +
> + ret = gpiochip_add_data(&gpio->chip, gpio);
> + if (ret < 0) {
> + dev_err(dev, "Unable to register gpiochip\n");
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static int pisosr_gpio_remove(struct spi_device *spi)
> +{
> + struct pisosr_gpio *gpio = spi_get_drvdata(spi);
> +
> + gpiochip_remove(&gpio->chip);
> +
> + mutex_destroy(&gpio->lock);
> +
> + return 0;
> +}
> +
> +static const struct spi_device_id pisosr_gpio_id_table[] = {
> + { "pisosr-gpio", },
> + { /* sentinel */ }
Please add this :-)
{"ti,sn65hvs885", 0},
> +};
> +MODULE_DEVICE_TABLE(spi, pisosr_gpio_id_table);
> +
> +static const struct of_device_id pisosr_gpio_of_match_table[] = {
> + { .compatible = "pisosr-gpio", },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, pisosr_gpio_of_match_table);
> +
> +static struct spi_driver pisosr_gpio_driver = {
> + .driver = {
> + .name = "pisosr-gpio",
> + .of_match_table = pisosr_gpio_of_match_table,
> + },
> + .probe = pisosr_gpio_probe,
> + .remove = pisosr_gpio_remove,
> + .id_table = pisosr_gpio_id_table,
> +};
> +module_spi_driver(pisosr_gpio_driver);
> +
> +MODULE_AUTHOR("Andrew F. Davis <afd@...com>");
> +MODULE_DESCRIPTION("SPI Compatible PISO Shift Register GPIO Driver");
> +MODULE_LICENSE("GPL v2");
Hi Andrew
I have created an driver for the sn65hvs885 at the same time as you, and
the output is nearly identical :-)
We are both missing the support for cacading devices, but i guess that
can come later on.
/Sean
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