Re: [PATCH v2 2/2] gpio: Add driver for SPI serializers

"Andrew F. Davis" <afd@xxxxxx> · Mon, 1 Feb 2016 08:52:02 -0600

On 01/29/2016 12:31 AM, Sean Nyekjær wrote:


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@xxxxxx>
---
  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@xxxxxx>
+ *
+ * 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},

See below.

+};
+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@xxxxxx>");
+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

Hi Sean,

This started as a driver for the sn65hvs88*2*, after seeing other drivers
for similar parts I found that these input shift-register devices interface
mostly the same way, so a more generic catch-all driver might be more
useful.

I would like to avoid explicitly putting the individual part names that may be
compatible in this driver for reasons described well by Rob's comment[0]. If
you disagree I don't have any real serious qualms with adding some part names.

Also by allowing a variable number of bits to be defined in DT I think
cascaded devices should work with this driver already.

[0] https://lkml.org/lkml/2016/1/28/581

Andrew
--
To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html






