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/driver.h>
  14 #include <linux/io.h>
  15 #include <linux/init.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
 126         spics = devm_kzalloc(&pdev->dev, sizeof(*spics), GFP_KERNEL);
 127         if (!spics)
 128                 return -ENOMEM;
 129
 130         spics->base = devm_platform_ioremap_resource(pdev, 0);
 131         if (IS_ERR(spics->base))
 132                 return PTR_ERR(spics->base);
 133
 134         if (of_property_read_u32(np, "st-spics,peripcfg-reg",
 135                                 &spics->perip_cfg))
 136                 goto err_dt_data;
 137         if (of_property_read_u32(np, "st-spics,sw-enable-bit",
 138                                 &spics->sw_enable_bit))
 139                 goto err_dt_data;
 140         if (of_property_read_u32(np, "st-spics,cs-value-bit",
 141                                 &spics->cs_value_bit))
 142                 goto err_dt_data;
 143         if (of_property_read_u32(np, "st-spics,cs-enable-mask",
 144                                 &spics->cs_enable_mask))
 145                 goto err_dt_data;
 146         if (of_property_read_u32(np, "st-spics,cs-enable-shift",
 147                                 &spics->cs_enable_shift))
 148                 goto err_dt_data;
 149
 150         spics->chip.ngpio = NUM_OF_GPIO;
 151         spics->chip.base = -1;
 152         spics->chip.request = spics_request;
 153         spics->chip.free = spics_free;
 154         spics->chip.direction_input = spics_direction_input;
 155         spics->chip.direction_output = spics_direction_output;
 156         spics->chip.get = spics_get_value;
 157         spics->chip.set = spics_set_value;
 158         spics->chip.label = dev_name(&pdev->dev);
 159         spics->chip.parent = &pdev->dev;
 160         spics->chip.owner = THIS_MODULE;
 161         spics->last_off = -1;
 162
 163         return devm_gpiochip_add_data(&pdev->dev, &spics->chip, spics);
 164
 165 err_dt_data:
 166         dev_err(&pdev->dev, "DT probe failed\n");
 167         return -EINVAL;
 168 }
 169
 170 static const struct of_device_id spics_gpio_of_match[] = {
 171         { .compatible = "st,spear-spics-gpio" },
 172         {}
 173 };
 174
 175 static struct platform_driver spics_gpio_driver = {
 176         .probe = spics_gpio_probe,
 177         .driver = {
 178                 .name = "spear-spics-gpio",
 179                 .of_match_table = spics_gpio_of_match,
 180         },
 181 };
 182
 183 static int __init spics_gpio_init(void)
 184 {
 185         return platform_driver_register(&spics_gpio_driver);
 186 }
 187 subsys_initcall(spics_gpio_init);