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

["Sean Nyekjær" <sean.nyekjaer@prevas.dk>]

On 2016-02-01 15:52, Andrew F. Davis wrote:
> 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@ti.com>

Tested-by: Sean Nyekjaer <sean.nyekjaer@prevas.dk>

>>> ---
>>>   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@ti.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},
>
> 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@ti.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
>
> 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

Hi Andrew

I have tested this with 2 sn65hvs885 cacaded and i does indeed work :-)

/Sean