1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * GPIO latch driver 4 * 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 and 37 * the number of inputs per latch is derived from the number of GPIOs given 38 * in the corresponding device tree properties. 39 */ 40 41 #include <linux/cleanup.h> 42 #include <linux/err.h> 43 #include <linux/gpio/consumer.h> 44 #include <linux/gpio/driver.h> 45 #include <linux/module.h> 46 #include <linux/platform_device.h> 47 #include <linux/property.h> 48 #include <linux/delay.h> 49 50 struct gpio_latch_priv { 51 struct gpio_chip gc; 52 struct gpio_descs *clk_gpios; 53 struct gpio_descs *latched_gpios; 54 int n_latched_gpios; 55 unsigned int setup_duration_ns; 56 unsigned int clock_duration_ns; 57 unsigned long *shadow; 58 /* 59 * Depending on whether any of the underlying GPIOs may sleep we either 60 * use a mutex or a spinlock to protect our shadow map. 61 */ 62 union { 63 struct mutex mutex; /* protects @shadow */ 64 spinlock_t spinlock; /* protects @shadow */ 65 }; 66 }; 67 68 static int gpio_latch_get_direction(struct gpio_chip *gc, unsigned int offset) 69 { 70 return GPIO_LINE_DIRECTION_OUT; 71 } 72 73 static int gpio_latch_set_unlocked(struct gpio_latch_priv *priv, 74 int (*set)(struct gpio_desc *desc, int value), 75 unsigned int offset, bool val) 76 { 77 int latch = offset / priv->n_latched_gpios, i, ret; 78 79 assign_bit(offset, priv->shadow, val); 80 81 for (i = 0; i < priv->n_latched_gpios; i++) { 82 ret = set(priv->latched_gpios->desc[i], 83 test_bit(latch * priv->n_latched_gpios + i, 84 priv->shadow)); 85 if (ret) 86 return ret; 87 } 88 89 ndelay(priv->setup_duration_ns); 90 set(priv->clk_gpios->desc[latch], 1); 91 ndelay(priv->clock_duration_ns); 92 set(priv->clk_gpios->desc[latch], 0); 93 94 return 0; 95 } 96 97 static int gpio_latch_set(struct gpio_chip *gc, unsigned int offset, int val) 98 { 99 struct gpio_latch_priv *priv = gpiochip_get_data(gc); 100 101 guard(spinlock_irqsave)(&priv->spinlock); 102 103 return gpio_latch_set_unlocked(priv, gpiod_set_value, offset, val); 104 } 105 106 static int gpio_latch_set_can_sleep(struct gpio_chip *gc, unsigned int offset, int val) 107 { 108 struct gpio_latch_priv *priv = gpiochip_get_data(gc); 109 110 guard(mutex)(&priv->mutex); 111 112 return gpio_latch_set_unlocked(priv, gpiod_set_value_cansleep, offset, val); 113 } 114 115 static bool gpio_latch_can_sleep(struct gpio_latch_priv *priv, unsigned int n_latches) 116 { 117 int i; 118 119 for (i = 0; i < n_latches; i++) 120 if (gpiod_cansleep(priv->clk_gpios->desc[i])) 121 return true; 122 123 for (i = 0; i < priv->n_latched_gpios; i++) 124 if (gpiod_cansleep(priv->latched_gpios->desc[i])) 125 return true; 126 127 return false; 128 } 129 130 /* 131 * Some value which is still acceptable to delay in atomic context. 132 * If we need to go higher we might have to switch to usleep_range(), 133 * but that cannot ne used in atomic context and the driver would have 134 * to be adjusted to support that. 135 */ 136 #define DURATION_NS_MAX 5000 137 138 static int gpio_latch_probe(struct platform_device *pdev) 139 { 140 struct device *dev = &pdev->dev; 141 struct gpio_latch_priv *priv; 142 unsigned int n_latches; 143 144 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); 145 if (!priv) 146 return -ENOMEM; 147 148 priv->clk_gpios = devm_gpiod_get_array(dev, "clk", GPIOD_OUT_LOW); 149 if (IS_ERR(priv->clk_gpios)) 150 return PTR_ERR(priv->clk_gpios); 151 152 priv->latched_gpios = devm_gpiod_get_array(dev, "latched", GPIOD_OUT_LOW); 153 if (IS_ERR(priv->latched_gpios)) 154 return PTR_ERR(priv->latched_gpios); 155 156 n_latches = priv->clk_gpios->ndescs; 157 priv->n_latched_gpios = priv->latched_gpios->ndescs; 158 159 priv->shadow = devm_bitmap_zalloc(dev, n_latches * priv->n_latched_gpios, 160 GFP_KERNEL); 161 if (!priv->shadow) 162 return -ENOMEM; 163 164 if (gpio_latch_can_sleep(priv, n_latches)) { 165 priv->gc.can_sleep = true; 166 priv->gc.set = gpio_latch_set_can_sleep; 167 mutex_init(&priv->mutex); 168 } else { 169 priv->gc.can_sleep = false; 170 priv->gc.set = gpio_latch_set; 171 spin_lock_init(&priv->spinlock); 172 } 173 174 device_property_read_u32(dev, "setup-duration-ns", 175 &priv->setup_duration_ns); 176 if (priv->setup_duration_ns > DURATION_NS_MAX) { 177 dev_warn(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 device_property_read_u32(dev, "clock-duration-ns", 183 &priv->clock_duration_ns); 184 if (priv->clock_duration_ns > DURATION_NS_MAX) { 185 dev_warn(dev, "clock-duration-ns too high, limit to %d\n", 186 DURATION_NS_MAX); 187 priv->clock_duration_ns = DURATION_NS_MAX; 188 } 189 190 priv->gc.get_direction = gpio_latch_get_direction; 191 priv->gc.ngpio = n_latches * priv->n_latched_gpios; 192 priv->gc.owner = THIS_MODULE; 193 priv->gc.base = -1; 194 priv->gc.parent = dev; 195 196 platform_set_drvdata(pdev, priv); 197 198 return devm_gpiochip_add_data(dev, &priv->gc, priv); 199 } 200 201 static const struct of_device_id gpio_latch_ids[] = { 202 { 203 .compatible = "gpio-latch", 204 }, 205 { /* sentinel */ } 206 }; 207 MODULE_DEVICE_TABLE(of, gpio_latch_ids); 208 209 static struct platform_driver gpio_latch_driver = { 210 .driver = { 211 .name = "gpio-latch", 212 .of_match_table = gpio_latch_ids, 213 }, 214 .probe = gpio_latch_probe, 215 }; 216 module_platform_driver(gpio_latch_driver); 217 218 MODULE_LICENSE("GPL v2"); 219 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>"); 220 MODULE_DESCRIPTION("GPIO latch driver"); 221