drivers/gpio/gpio-spear-spics.c

   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");