1 /* 2 * SPEAr platform SPI chipselect abstraction over gpiolib 3 * 4 * Copyright (C) 2012 ST Microelectronics 5 * Shiraz Hashim <shiraz.linux.kernel@gmail.com> 6 * 7 * This file is licensed under the terms of the GNU General Public 8 * License version 2. This program is licensed "as is" without any 9 * warranty of any kind, whether express or implied. 10 */ 11 12 #include <linux/err.h> 13 #include <linux/gpio.h> 14 #include <linux/io.h> 15 #include <linux/module.h> 16 #include <linux/of.h> 17 #include <linux/platform_device.h> 18 #include <linux/types.h> 19 20 /* maximum chipselects */ 21 #define NUM_OF_GPIO 4 22 23 /* 24 * Provision is available on some SPEAr SoCs to control ARM PL022 spi cs 25 * through system registers. This register lies outside spi (pl022) 26 * address space into system registers. 27 * 28 * It provides control for spi chip select lines so that any chipselect 29 * (out of 4 possible chipselects in pl022) can be made low to select 30 * the particular slave. 31 */ 32 33 /** 34 * struct spear_spics - represents spi chip select control 35 * @base: base address 36 * @perip_cfg: configuration register 37 * @sw_enable_bit: bit to enable s/w control over chipselects 38 * @cs_value_bit: bit to program high or low chipselect 39 * @cs_enable_mask: mask to select bits required to select chipselect 40 * @cs_enable_shift: bit pos of cs_enable_mask 41 * @use_count: use count of a spi controller cs lines 42 * @last_off: stores last offset caller of set_value() 43 * @chip: gpio_chip abstraction 44 */ 45 struct spear_spics { 46 void __iomem *base; 47 u32 perip_cfg; 48 u32 sw_enable_bit; 49 u32 cs_value_bit; 50 u32 cs_enable_mask; 51 u32 cs_enable_shift; 52 unsigned long use_count; 53 int last_off; 54 struct gpio_chip chip; 55 }; 56 57 /* gpio framework specific routines */ 58 static int spics_get_value(struct gpio_chip *chip, unsigned offset) 59 { 60 return -ENXIO; 61 } 62 63 static void spics_set_value(struct gpio_chip *chip, unsigned offset, int value) 64 { 65 struct spear_spics *spics = container_of(chip, struct spear_spics, 66 chip); 67 u32 tmp; 68 69 /* select chip select from register */ 70 tmp = readl_relaxed(spics->base + spics->perip_cfg); 71 if (spics->last_off != offset) { 72 spics->last_off = offset; 73 tmp &= ~(spics->cs_enable_mask << spics->cs_enable_shift); 74 tmp |= offset << spics->cs_enable_shift; 75 } 76 77 /* toggle chip select line */ 78 tmp &= ~(0x1 << spics->cs_value_bit); 79 tmp |= value << spics->cs_value_bit; 80 writel_relaxed(tmp, spics->base + spics->perip_cfg); 81 } 82 83 static int spics_direction_input(struct gpio_chip *chip, unsigned offset) 84 { 85 return -ENXIO; 86 } 87 88 static int spics_direction_output(struct gpio_chip *chip, unsigned offset, 89 int value) 90 { 91 spics_set_value(chip, offset, value); 92 return 0; 93 } 94 95 static int spics_request(struct gpio_chip *chip, unsigned offset) 96 { 97 struct spear_spics *spics = container_of(chip, struct spear_spics, 98 chip); 99 u32 tmp; 100 101 if (!spics->use_count++) { 102 tmp = readl_relaxed(spics->base + spics->perip_cfg); 103 tmp |= 0x1 << spics->sw_enable_bit; 104 tmp |= 0x1 << spics->cs_value_bit; 105 writel_relaxed(tmp, spics->base + spics->perip_cfg); 106 } 107 108 return 0; 109 } 110 111 static void spics_free(struct gpio_chip *chip, unsigned offset) 112 { 113 struct spear_spics *spics = container_of(chip, struct spear_spics, 114 chip); 115 u32 tmp; 116 117 if (!--spics->use_count) { 118 tmp = readl_relaxed(spics->base + spics->perip_cfg); 119 tmp &= ~(0x1 << spics->sw_enable_bit); 120 writel_relaxed(tmp, spics->base + spics->perip_cfg); 121 } 122 } 123 124 static int spics_gpio_probe(struct platform_device *pdev) 125 { 126 struct device_node *np = pdev->dev.of_node; 127 struct spear_spics *spics; 128 struct resource *res; 129 int ret; 130 131 spics = devm_kzalloc(&pdev->dev, sizeof(*spics), GFP_KERNEL); 132 if (!spics) 133 return -ENOMEM; 134 135 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 136 spics->base = devm_ioremap_resource(&pdev->dev, res); 137 if (IS_ERR(spics->base)) 138 return PTR_ERR(spics->base); 139 140 if (of_property_read_u32(np, "st-spics,peripcfg-reg", 141 &spics->perip_cfg)) 142 goto err_dt_data; 143 if (of_property_read_u32(np, "st-spics,sw-enable-bit", 144 &spics->sw_enable_bit)) 145 goto err_dt_data; 146 if (of_property_read_u32(np, "st-spics,cs-value-bit", 147 &spics->cs_value_bit)) 148 goto err_dt_data; 149 if (of_property_read_u32(np, "st-spics,cs-enable-mask", 150 &spics->cs_enable_mask)) 151 goto err_dt_data; 152 if (of_property_read_u32(np, "st-spics,cs-enable-shift", 153 &spics->cs_enable_shift)) 154 goto err_dt_data; 155 156 platform_set_drvdata(pdev, spics); 157 158 spics->chip.ngpio = NUM_OF_GPIO; 159 spics->chip.base = -1; 160 spics->chip.request = spics_request; 161 spics->chip.free = spics_free; 162 spics->chip.direction_input = spics_direction_input; 163 spics->chip.direction_output = spics_direction_output; 164 spics->chip.get = spics_get_value; 165 spics->chip.set = spics_set_value; 166 spics->chip.label = dev_name(&pdev->dev); 167 spics->chip.dev = &pdev->dev; 168 spics->chip.owner = THIS_MODULE; 169 spics->last_off = -1; 170 171 ret = gpiochip_add(&spics->chip); 172 if (ret) { 173 dev_err(&pdev->dev, "unable to add gpio chip\n"); 174 return ret; 175 } 176 177 dev_info(&pdev->dev, "spear spics registered\n"); 178 return 0; 179 180 err_dt_data: 181 dev_err(&pdev->dev, "DT probe failed\n"); 182 return -EINVAL; 183 } 184 185 static const struct of_device_id spics_gpio_of_match[] = { 186 { .compatible = "st,spear-spics-gpio" }, 187 {} 188 }; 189 MODULE_DEVICE_TABLE(of, spics_gpio_of_match); 190 191 static struct platform_driver spics_gpio_driver = { 192 .probe = spics_gpio_probe, 193 .driver = { 194 .name = "spear-spics-gpio", 195 .of_match_table = spics_gpio_of_match, 196 }, 197 }; 198 199 static int __init spics_gpio_init(void) 200 { 201 return platform_driver_register(&spics_gpio_driver); 202 } 203 subsys_initcall(spics_gpio_init); 204 205 MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>"); 206 MODULE_DESCRIPTION("STMicroelectronics SPEAr SPI Chip Select Abstraction"); 207 MODULE_LICENSE("GPL"); 208