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 = gpiochip_get_data(chip); 66 u32 tmp; 67 68 /* select chip select from register */ 69 tmp = readl_relaxed(spics->base + spics->perip_cfg); 70 if (spics->last_off != offset) { 71 spics->last_off = offset; 72 tmp &= ~(spics->cs_enable_mask << spics->cs_enable_shift); 73 tmp |= offset << spics->cs_enable_shift; 74 } 75 76 /* toggle chip select line */ 77 tmp &= ~(0x1 << spics->cs_value_bit); 78 tmp |= value << spics->cs_value_bit; 79 writel_relaxed(tmp, spics->base + spics->perip_cfg); 80 } 81 82 static int spics_direction_input(struct gpio_chip *chip, unsigned offset) 83 { 84 return -ENXIO; 85 } 86 87 static int spics_direction_output(struct gpio_chip *chip, unsigned offset, 88 int value) 89 { 90 spics_set_value(chip, offset, value); 91 return 0; 92 } 93 94 static int spics_request(struct gpio_chip *chip, unsigned offset) 95 { 96 struct spear_spics *spics = gpiochip_get_data(chip); 97 u32 tmp; 98 99 if (!spics->use_count++) { 100 tmp = readl_relaxed(spics->base + spics->perip_cfg); 101 tmp |= 0x1 << spics->sw_enable_bit; 102 tmp |= 0x1 << spics->cs_value_bit; 103 writel_relaxed(tmp, spics->base + spics->perip_cfg); 104 } 105 106 return 0; 107 } 108 109 static void spics_free(struct gpio_chip *chip, unsigned offset) 110 { 111 struct spear_spics *spics = gpiochip_get_data(chip); 112 u32 tmp; 113 114 if (!--spics->use_count) { 115 tmp = readl_relaxed(spics->base + spics->perip_cfg); 116 tmp &= ~(0x1 << spics->sw_enable_bit); 117 writel_relaxed(tmp, spics->base + spics->perip_cfg); 118 } 119 } 120 121 static int spics_gpio_probe(struct platform_device *pdev) 122 { 123 struct device_node *np = pdev->dev.of_node; 124 struct spear_spics *spics; 125 struct resource *res; 126 int ret; 127 128 spics = devm_kzalloc(&pdev->dev, sizeof(*spics), GFP_KERNEL); 129 if (!spics) 130 return -ENOMEM; 131 132 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 133 spics->base = devm_ioremap_resource(&pdev->dev, res); 134 if (IS_ERR(spics->base)) 135 return PTR_ERR(spics->base); 136 137 if (of_property_read_u32(np, "st-spics,peripcfg-reg", 138 &spics->perip_cfg)) 139 goto err_dt_data; 140 if (of_property_read_u32(np, "st-spics,sw-enable-bit", 141 &spics->sw_enable_bit)) 142 goto err_dt_data; 143 if (of_property_read_u32(np, "st-spics,cs-value-bit", 144 &spics->cs_value_bit)) 145 goto err_dt_data; 146 if (of_property_read_u32(np, "st-spics,cs-enable-mask", 147 &spics->cs_enable_mask)) 148 goto err_dt_data; 149 if (of_property_read_u32(np, "st-spics,cs-enable-shift", 150 &spics->cs_enable_shift)) 151 goto err_dt_data; 152 153 platform_set_drvdata(pdev, spics); 154 155 spics->chip.ngpio = NUM_OF_GPIO; 156 spics->chip.base = -1; 157 spics->chip.request = spics_request; 158 spics->chip.free = spics_free; 159 spics->chip.direction_input = spics_direction_input; 160 spics->chip.direction_output = spics_direction_output; 161 spics->chip.get = spics_get_value; 162 spics->chip.set = spics_set_value; 163 spics->chip.label = dev_name(&pdev->dev); 164 spics->chip.parent = &pdev->dev; 165 spics->chip.owner = THIS_MODULE; 166 spics->last_off = -1; 167 168 ret = gpiochip_add_data(&spics->chip, spics); 169 if (ret) { 170 dev_err(&pdev->dev, "unable to add gpio chip\n"); 171 return ret; 172 } 173 174 dev_info(&pdev->dev, "spear spics registered\n"); 175 return 0; 176 177 err_dt_data: 178 dev_err(&pdev->dev, "DT probe failed\n"); 179 return -EINVAL; 180 } 181 182 static const struct of_device_id spics_gpio_of_match[] = { 183 { .compatible = "st,spear-spics-gpio" }, 184 {} 185 }; 186 MODULE_DEVICE_TABLE(of, spics_gpio_of_match); 187 188 static struct platform_driver spics_gpio_driver = { 189 .probe = spics_gpio_probe, 190 .driver = { 191 .name = "spear-spics-gpio", 192 .of_match_table = spics_gpio_of_match, 193 }, 194 }; 195 196 static int __init spics_gpio_init(void) 197 { 198 return platform_driver_register(&spics_gpio_driver); 199 } 200 subsys_initcall(spics_gpio_init); 201 202 MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>"); 203 MODULE_DESCRIPTION("STMicroelectronics SPEAr SPI Chip Select Abstraction"); 204 MODULE_LICENSE("GPL"); 205