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1// SPDX-License-Identifier: GPL-2.02/*3 * GPIO latch driver4 *5 * Copyright (C) 2022 Sascha Hauer <s.hauer@pengutronix.de>6 *7 * This driver implements a GPIO (or better GPO as there is no input)8 * multiplexer based on latches like this:9 *10 * CLK0 ----------------------. ,--------.11 * CLK1 -------------------. `--------|> #0 |12 * | | |13 * OUT0 ----------------+--|-----------|D0 Q0|-----|<14 * OUT1 --------------+-|--|-----------|D1 Q1|-----|<15 * OUT2 ------------+-|-|--|-----------|D2 Q2|-----|<16 * OUT3 ----------+-|-|-|--|-----------|D3 Q3|-----|<17 * OUT4 --------+-|-|-|-|--|-----------|D4 Q4|-----|<18 * OUT5 ------+-|-|-|-|-|--|-----------|D5 Q5|-----|<19 * OUT6 ----+-|-|-|-|-|-|--|-----------|D6 Q6|-----|<20 * OUT7 --+-|-|-|-|-|-|-|--|-----------|D7 Q7|-----|<21 * | | | | | | | | | `--------'22 * | | | | | | | | |23 * | | | | | | | | | ,--------.24 * | | | | | | | | `-----------|> #1 |25 * | | | | | | | | | |26 * | | | | | | | `--------------|D0 Q0|-----|<27 * | | | | | | `----------------|D1 Q1|-----|<28 * | | | | | `------------------|D2 Q2|-----|<29 * | | | | `--------------------|D3 Q3|-----|<30 * | | | `----------------------|D4 Q4|-----|<31 * | | `------------------------|D5 Q5|-----|<32 * | `--------------------------|D6 Q6|-----|<33 * `----------------------------|D7 Q7|-----|<34 * `--------'35 *36 * The above is just an example. The actual number of number of latches and37 * the number of inputs per latch is derived from the number of GPIOs given38 * in the corresponding device tree properties.39 */40 41#include <linux/err.h>42#include <linux/gpio/consumer.h>43#include <linux/gpio/driver.h>44#include <linux/module.h>45#include <linux/mod_devicetable.h>46#include <linux/platform_device.h>47#include <linux/delay.h>48 49#include "gpiolib.h"50 51struct gpio_latch_priv {52 struct gpio_chip gc;53 struct gpio_descs *clk_gpios;54 struct gpio_descs *latched_gpios;55 int n_latched_gpios;56 unsigned int setup_duration_ns;57 unsigned int clock_duration_ns;58 unsigned long *shadow;59 /*60 * Depending on whether any of the underlying GPIOs may sleep we either61 * use a mutex or a spinlock to protect our shadow map.62 */63 union {64 struct mutex mutex; /* protects @shadow */65 spinlock_t spinlock; /* protects @shadow */66 };67};68 69static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset)70{71 return GPIO_LINE_DIRECTION_OUT;72}73 74static void gpio_latch_set_unlocked(struct gpio_latch_priv *priv,75 void (*set)(struct gpio_desc *desc, int value),76 unsigned int offset, bool val)77{78 int latch = offset / priv->n_latched_gpios;79 int i;80 81 assign_bit(offset, priv->shadow, val);82 83 for (i = 0; i < priv->n_latched_gpios; i++)84 set(priv->latched_gpios->desc[i],85 test_bit(latch * priv->n_latched_gpios + i, priv->shadow));86 87 ndelay(priv->setup_duration_ns);88 set(priv->clk_gpios->desc[latch], 1);89 ndelay(priv->clock_duration_ns);90 set(priv->clk_gpios->desc[latch], 0);91}92 93static void gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val)94{95 struct gpio_latch_priv *priv = gpiochip_get_data(gc);96 unsigned long flags;97 98 spin_lock_irqsave(&priv->spinlock, flags);99 100 gpio_latch_set_unlocked(priv, gpiod_set_value, offset, val);101 102 spin_unlock_irqrestore(&priv->spinlock, flags);103}104 105static void gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val)106{107 struct gpio_latch_priv *priv = gpiochip_get_data(gc);108 109 mutex_lock(&priv->mutex);110 111 gpio_latch_set_unlocked(priv, gpiod_set_value_cansleep, offset, val);112 113 mutex_unlock(&priv->mutex);114}115 116static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv, unsigned int n_latches)117{118 int i;119 120 for (i = 0; i < n_latches; i++)121 if (gpiod_cansleep(priv->clk_gpios->desc[i]))122 return true;123 124 for (i = 0; i < priv->n_latched_gpios; i++)125 if (gpiod_cansleep(priv->latched_gpios->desc[i]))126 return true;127 128 return false;129}130 131/*132 * Some value which is still acceptable to delay in atomic context.133 * If we need to go higher we might have to switch to usleep_range(),134 * but that cannot ne used in atomic context and the driver would have135 * to be adjusted to support that.136 */137#define DURATION_NS_MAX 5000138 139static int gpio_latch_probe(struct platform_device *pdev)140{141 struct gpio_latch_priv *priv;142 unsigned int n_latches;143 struct device_node *np = pdev->dev.of_node;144 145 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);146 if (!priv)147 return -ENOMEM;148 149 priv->clk_gpios = devm_gpiod_get_array(&pdev->dev, "clk", GPIOD_OUT_LOW);150 if (IS_ERR(priv->clk_gpios))151 return PTR_ERR(priv->clk_gpios);152 153 priv->latched_gpios = devm_gpiod_get_array(&pdev->dev, "latched", GPIOD_OUT_LOW);154 if (IS_ERR(priv->latched_gpios))155 return PTR_ERR(priv->latched_gpios);156 157 n_latches = priv->clk_gpios->ndescs;158 priv->n_latched_gpios = priv->latched_gpios->ndescs;159 160 priv->shadow = devm_bitmap_zalloc(&pdev->dev, n_latches * priv->n_latched_gpios,161 GFP_KERNEL);162 if (!priv->shadow)163 return -ENOMEM;164 165 if (gpio_latch_can_sleep(priv, n_latches)) {166 priv->gc.can_sleep = true;167 priv->gc.set = gpio_latch_set_can_sleep;168 mutex_init(&priv->mutex);169 } else {170 priv->gc.can_sleep = false;171 priv->gc.set = gpio_latch_set;172 spin_lock_init(&priv->spinlock);173 }174 175 of_property_read_u32(np, "setup-duration-ns", &priv->setup_duration_ns);176 if (priv->setup_duration_ns > DURATION_NS_MAX) {177 dev_warn(&pdev->dev, "setup-duration-ns too high, limit to %d\n",178 DURATION_NS_MAX);179 priv->setup_duration_ns = DURATION_NS_MAX;180 }181 182 of_property_read_u32(np, "clock-duration-ns", &priv->clock_duration_ns);183 if (priv->clock_duration_ns > DURATION_NS_MAX) {184 dev_warn(&pdev->dev, "clock-duration-ns too high, limit to %d\n",185 DURATION_NS_MAX);186 priv->clock_duration_ns = DURATION_NS_MAX;187 }188 189 priv->gc.get_direction = gpio_latch_get_direction;190 priv->gc.ngpio = n_latches * priv->n_latched_gpios;191 priv->gc.owner = THIS_MODULE;192 priv->gc.base = -1;193 priv->gc.parent = &pdev->dev;194 195 platform_set_drvdata(pdev, priv);196 197 return devm_gpiochip_add_data(&pdev->dev, &priv->gc, priv);198}199 200static const struct of_device_id gpio_latch_ids[] = {201 {202 .compatible = "gpio-latch",203 },204 { /* sentinel */ }205};206MODULE_DEVICE_TABLE(of, gpio_latch_ids);207 208static struct platform_driver gpio_latch_driver = {209 .driver = {210 .name = "gpio-latch",211 .of_match_table = gpio_latch_ids,212 },213 .probe = gpio_latch_probe,214};215module_platform_driver(gpio_latch_driver);216 217MODULE_LICENSE("GPL v2");218MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");219MODULE_DESCRIPTION("GPIO latch driver");220