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Date: Wed, 31 Aug 2022 10:01:09 +0200
From: Marco Felsch <m.felsch@...gutronix.de>
To: Sascha Hauer <s.hauer@...gutronix.de>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
Geert Uytterhoeven <geert@...ux-m68k.org>,
kernel@...gutronix.de, Bartosz Golaszewski <brgl@...ev.pl>,
Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v2 1/2] gpio: Add gpio latch driver
Hi Sascha,
On 22-08-31, Sascha Hauer wrote:
> This driver implements a GPIO multiplexer based on latches connected to
> other GPIOs. A set of data GPIOs is connected to the data input of
> multiple latches. The clock input of each latch is driven by another
> set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
> 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
> are output only.
>
> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
apart the one minor nit (see end) feel free to add my
Reviewed-by: Marco Felsch <m.felsch@...gutronix.de>
> ---
> drivers/gpio/Kconfig | 6 ++
> drivers/gpio/Makefile | 1 +
> drivers/gpio/gpio-latch.c | 190 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 197 insertions(+)
> create mode 100644 drivers/gpio/gpio-latch.c
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 0642f579196f2..e4603810ec910 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -1690,6 +1690,12 @@ config GPIO_AGGREGATOR
> industrial control context, to be operated from userspace using
> the GPIO chardev interface.
>
> +config GPIO_LATCH
> + tristate "GPIO latch driver"
> + help
> + Say yes here to enable a driver for GPIO multiplexers based on latches
> + connected to other GPIOs.
> +
> config GPIO_MOCKUP
> tristate "GPIO Testing Driver"
> select IRQ_SIM
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index a0985d30f51bb..310fa08decc69 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -75,6 +75,7 @@ obj-$(CONFIG_GPIO_IT87) += gpio-it87.o
> obj-$(CONFIG_GPIO_IXP4XX) += gpio-ixp4xx.o
> obj-$(CONFIG_GPIO_JANZ_TTL) += gpio-janz-ttl.o
> obj-$(CONFIG_GPIO_KEMPLD) += gpio-kempld.o
> +obj-$(CONFIG_GPIO_LATCH) += gpio-latch.o
> obj-$(CONFIG_GPIO_LOGICVC) += gpio-logicvc.o
> obj-$(CONFIG_GPIO_LOONGSON1) += gpio-loongson1.o
> obj-$(CONFIG_GPIO_LOONGSON) += gpio-loongson.o
> diff --git a/drivers/gpio/gpio-latch.c b/drivers/gpio/gpio-latch.c
> new file mode 100644
> index 0000000000000..4068ed4066272
> --- /dev/null
> +++ b/drivers/gpio/gpio-latch.c
> @@ -0,0 +1,190 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * GPIO latch driver
> + *
> + * Copyright (C) 2022 Sascha Hauer <s.hauer@...gutronix.de>
> + *
> + * This driver implements a GPIO (or better GPO as there is no input)
> + * multiplexer based on latches like this:
> + *
> + * CLK0 ----------------------. ,--------.
> + * CLK1 -------------------. `--------|> #0 |
> + * | | |
> + * OUT0 ----------------+--|-----------|D0 Q0|-----|<
> + * OUT1 --------------+-|--|-----------|D1 Q1|-----|<
> + * OUT2 ------------+-|-|--|-----------|D2 Q2|-----|<
> + * OUT3 ----------+-|-|-|--|-----------|D3 Q3|-----|<
> + * OUT4 --------+-|-|-|-|--|-----------|D4 Q4|-----|<
> + * OUT5 ------+-|-|-|-|-|--|-----------|D5 Q5|-----|<
> + * OUT6 ----+-|-|-|-|-|-|--|-----------|D6 Q6|-----|<
> + * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7 Q7|-----|<
> + * | | | | | | | | | `--------'
> + * | | | | | | | | |
> + * | | | | | | | | | ,--------.
> + * | | | | | | | | `-----------|> #1 |
> + * | | | | | | | | | |
> + * | | | | | | | `--------------|D0 Q0|-----|<
> + * | | | | | | `----------------|D1 Q1|-----|<
> + * | | | | | `------------------|D2 Q2|-----|<
> + * | | | | `--------------------|D3 Q3|-----|<
> + * | | | `----------------------|D4 Q4|-----|<
> + * | | `------------------------|D5 Q5|-----|<
> + * | `--------------------------|D6 Q6|-----|<
> + * `----------------------------|D7 Q7|-----|<
> + * `--------'
> + *
> + * The above is just an example. The actual number of number of latches and
> + * the number of inputs per latch is derived from the number of GPIOs given
> + * in the corresponding device tree properties.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/platform_device.h>
> +#include <linux/gpio/consumer.h>
> +
> +#include "gpiolib.h"
> +
> +struct gpio_latch_priv {
> + struct gpio_chip gc;
> + struct gpio_descs *clk_gpios;
> + struct gpio_descs *data_gpios;
> + spinlock_t lock;
> + int n_ports;
> + int n_pins;
> + unsigned int *shadow;
> + struct mutex mutex;
> + spinlock_t spinlock;
> +};
> +
> +static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)
> +{
> + return GPIO_LINE_DIRECTION_OUT;
> +}
> +
> +static void __gpio_latch_set(struct gpio_latch_priv *priv,
> + void (* set)(struct gpio_desc *desc, int value),
> + unsigned int offset, int val)
> +{
> + int latch = offset / priv->n_pins;
> + int i;
> +
> + if (val)
> + priv->shadow[latch] |= BIT(offset % priv->n_pins);
> + else
> + priv->shadow[latch] &= ~BIT(offset % priv->n_pins);
> +
> + for (i = 0; i < priv->n_pins; i++)
> + set(priv->data_gpios->desc[i], priv->shadow[latch] & BIT(i));
> +
> + set(priv->clk_gpios->desc[latch], 1);
> + set(priv->clk_gpios->desc[latch], 0);
> +}
> +
> +static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)
> +{
> + struct gpio_latch_priv *priv = gpiochip_get_data(gc);
> + unsigned long flags;
> +
> + spin_lock_irqsave(&priv->spinlock, flags);
> +
> + __gpio_latch_set(priv, gpiod_set_value, offset, val);
> +
> + spin_unlock_irqrestore(&priv->spinlock, flags);
> +}
> +
> +static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)
> +{
> + struct gpio_latch_priv *priv = gpiochip_get_data(gc);
> +
> + mutex_lock(&priv->mutex);
> +
> + __gpio_latch_set(priv, gpiod_set_value_cansleep, offset, val);
> +
> + mutex_unlock(&priv->mutex);
> +}
> +
> +static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv)
> +{
> + int i;
> +
> + for (i = 0; i < priv->n_ports; i++)
> + if (gpiod_cansleep(priv->clk_gpios->desc[i]))
> + return true;
> +
> + for (i = 0; i < priv->n_pins; i++)
> + if (gpiod_cansleep(priv->data_gpios->desc[i]))
> + return true;
> +
> + return false;
> +}
> +
> +static int gpio_latch_probe(struct platform_device *pdev)
> +{
> + struct gpio_latch_priv *priv;
> +
> + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + priv->clk_gpios = devm_gpiod_get_array(&pdev->dev, "clk", GPIOD_OUT_LOW);
> + if (IS_ERR(priv->clk_gpios))
> + return PTR_ERR(priv->clk_gpios);
> +
> + priv->data_gpios = devm_gpiod_get_array(&pdev->dev, "data", GPIOD_OUT_LOW);
> + if (IS_ERR(priv->data_gpios))
> + return PTR_ERR(priv->data_gpios);
> +
> + priv->n_ports = priv->clk_gpios->ndescs;
> + priv->n_pins = priv->data_gpios->ndescs;
> +
> + priv->shadow = devm_kcalloc(&pdev->dev, priv->n_ports, sizeof(*priv->shadow),
> + GFP_KERNEL);
> + if (!priv->shadow)
> + return -ENOMEM;
> +
> + if (gpio_latch_can_sleep(priv)) {
> + priv->gc.can_sleep = true;
> + priv->gc.set = gpio_latch_set_can_sleep;
> + mutex_init(&priv->mutex);
> + } else {
> + priv->gc.can_sleep = false;
> + priv->gc.set = gpio_latch_set;
> + spin_lock_init(&priv->spinlock);
> + }
> +
> + priv->gc.get_direction = gpio_latch_get_direction;
> + priv->gc.ngpio = priv->n_ports * priv->n_pins;
> + priv->gc.owner = THIS_MODULE;
> + priv->gc.base = -1;
> + priv->gc.parent = &pdev->dev;
> + priv->gc.of_node = pdev->dev.of_node;
> +
> + platform_set_drvdata(pdev, priv);
> +
> + return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv);
> +}
> +
> +static const struct of_device_id gpio_latch_ids[] = {
> + {
> + .compatible = "gpio-latch",
> + }, {
> + /* sentinel */
> + }
> +};
> +MODULE_DEVICE_TABLE(of, gpio_latch_ids);
> +
> +static struct platform_driver gpio_latch_driver = {
> + .driver = {
> + .name = "gpio-latch",
> + .of_match_table = gpio_latch_ids,
> + },
> + .probe = gpio_latch_probe,
> +};
> +module_platform_driver(gpio_latch_driver);
> +
> +MODULE_LICENSE("GPL v2");
checkpatch.pl should complain about this since it it now GPL, see commit
bf7fbeeae6db. Sorry for not spotted that earlier.
Regards,
Marco
> +MODULE_AUTHOR("Sascha Hauer <s.hauer@...gutronix.de>");
> +MODULE_DESCRIPTION("GPIO latch driver");
> --
> 2.30.2
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