diff options
Diffstat (limited to 'drivers/gpio/gpio-spear-spics.c')
| -rw-r--r-- | drivers/gpio/gpio-spear-spics.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/drivers/gpio/gpio-spear-spics.c b/drivers/gpio/gpio-spear-spics.c new file mode 100644 index 0000000..5f45fc4 --- /dev/null +++ b/drivers/gpio/gpio-spear-spics.c @@ -0,0 +1,217 @@ +/* + * SPEAr platform SPI chipselect abstraction over gpiolib + * + * Copyright (C) 2012 ST Microelectronics + * Shiraz Hashim <shiraz.hashim@st.com> + * + * This file is licensed under the terms of the GNU General Public + * License version 2. This program is licensed "as is" without any + * warranty of any kind, whether express or implied. + */ + +#include <linux/err.h> +#include <linux/gpio.h> +#include <linux/io.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/types.h> + +/* maximum chipselects */ +#define NUM_OF_GPIO 4 + +/* + * Provision is available on some SPEAr SoCs to control ARM PL022 spi cs + * through system registers. This register lies outside spi (pl022) + * address space into system registers. + * + * It provides control for spi chip select lines so that any chipselect + * (out of 4 possible chipselects in pl022) can be made low to select + * the particular slave. + */ + +/** + * struct spear_spics - represents spi chip select control + * @base: base address + * @perip_cfg: configuration register + * @sw_enable_bit: bit to enable s/w control over chipselects + * @cs_value_bit: bit to program high or low chipselect + * @cs_enable_mask: mask to select bits required to select chipselect + * @cs_enable_shift: bit pos of cs_enable_mask + * @use_count: use count of a spi controller cs lines + * @last_off: stores last offset caller of set_value() + * @chip: gpio_chip abstraction + */ +struct spear_spics { + void __iomem *base; + u32 perip_cfg; + u32 sw_enable_bit; + u32 cs_value_bit; + u32 cs_enable_mask; + u32 cs_enable_shift; + unsigned long use_count; + int last_off; + struct gpio_chip chip; +}; + +/* gpio framework specific routines */ +static int spics_get_value(struct gpio_chip *chip, unsigned offset) +{ + return -ENXIO; +} + +static void spics_set_value(struct gpio_chip *chip, unsigned offset, int value) +{ + struct spear_spics *spics = container_of(chip, struct spear_spics, + chip); + u32 tmp; + + /* select chip select from register */ + tmp = readl_relaxed(spics->base + spics->perip_cfg); + if (spics->last_off != offset) { + spics->last_off = offset; + tmp &= ~(spics->cs_enable_mask << spics->cs_enable_shift); + tmp |= offset << spics->cs_enable_shift; + } + + /* toggle chip select line */ + tmp &= ~(0x1 << spics->cs_value_bit); + tmp |= value << spics->cs_value_bit; + writel_relaxed(tmp, spics->base + spics->perip_cfg); +} + +static int spics_direction_input(struct gpio_chip *chip, unsigned offset) +{ + return -ENXIO; +} + +static int spics_direction_output(struct gpio_chip *chip, unsigned offset, + int value) +{ + spics_set_value(chip, offset, value); + return 0; +} + +static int spics_request(struct gpio_chip *chip, unsigned offset) +{ + struct spear_spics *spics = container_of(chip, struct spear_spics, + chip); + u32 tmp; + + if (!spics->use_count++) { + tmp = readl_relaxed(spics->base + spics->perip_cfg); + tmp |= 0x1 << spics->sw_enable_bit; + tmp |= 0x1 << spics->cs_value_bit; + writel_relaxed(tmp, spics->base + spics->perip_cfg); + } + + return 0; +} + +static void spics_free(struct gpio_chip *chip, unsigned offset) +{ + struct spear_spics *spics = container_of(chip, struct spear_spics, + chip); + u32 tmp; + + if (!--spics->use_count) { + tmp = readl_relaxed(spics->base + spics->perip_cfg); + tmp &= ~(0x1 << spics->sw_enable_bit); + writel_relaxed(tmp, spics->base + spics->perip_cfg); + } +} + +static int spics_gpio_probe(struct platform_device *pdev) +{ + struct device_node *np = pdev->dev.of_node; + struct spear_spics *spics; + struct resource *res; + int ret; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + if (!res) { + dev_err(&pdev->dev, "invalid IORESOURCE_MEM\n"); + return -EBUSY; + } + + spics = devm_kzalloc(&pdev->dev, sizeof(*spics), GFP_KERNEL); + if (!spics) { + dev_err(&pdev->dev, "memory allocation fail\n"); + return -ENOMEM; + } + + spics->base = devm_request_and_ioremap(&pdev->dev, res); + if (!spics->base) { + dev_err(&pdev->dev, "request and ioremap fail\n"); + return -ENOMEM; + } + + if (of_property_read_u32(np, "st-spics,peripcfg-reg", + &spics->perip_cfg)) + goto err_dt_data; + if (of_property_read_u32(np, "st-spics,sw-enable-bit", + &spics->sw_enable_bit)) + goto err_dt_data; + if (of_property_read_u32(np, "st-spics,cs-value-bit", + &spics->cs_value_bit)) + goto err_dt_data; + if (of_property_read_u32(np, "st-spics,cs-enable-mask", + &spics->cs_enable_mask)) + goto err_dt_data; + if (of_property_read_u32(np, "st-spics,cs-enable-shift", + &spics->cs_enable_shift)) + goto err_dt_data; + + platform_set_drvdata(pdev, spics); + + spics->chip.ngpio = NUM_OF_GPIO; + spics->chip.base = -1; + spics->chip.request = spics_request; + spics->chip.free = spics_free; + spics->chip.direction_input = spics_direction_input; + spics->chip.direction_output = spics_direction_output; + spics->chip.get = spics_get_value; + spics->chip.set = spics_set_value; + spics->chip.label = dev_name(&pdev->dev); + spics->chip.dev = &pdev->dev; + spics->chip.owner = THIS_MODULE; + spics->last_off = -1; + + ret = gpiochip_add(&spics->chip); + if (ret) { + dev_err(&pdev->dev, "unable to add gpio chip\n"); + return ret; + } + + dev_info(&pdev->dev, "spear spics registered\n"); + return 0; + +err_dt_data: + dev_err(&pdev->dev, "DT probe failed\n"); + return -EINVAL; +} + +static const struct of_device_id spics_gpio_of_match[] = { + { .compatible = "st,spear-spics-gpio" }, + {} +}; +MODULE_DEVICE_TABLE(of, spics_gpio_of_match); + +static struct platform_driver spics_gpio_driver = { + .probe = spics_gpio_probe, + .driver = { + .owner = THIS_MODULE, + .name = "spear-spics-gpio", + .of_match_table = spics_gpio_of_match, + }, +}; + +static int __init spics_gpio_init(void) +{ + return platform_driver_register(&spics_gpio_driver); +} +subsys_initcall(spics_gpio_init); + +MODULE_AUTHOR("Shiraz Hashim <shiraz.hashim@st.com>"); +MODULE_DESCRIPTION("ST Microlectronics SPEAr SPI Chip Select Abstraction"); +MODULE_LICENSE("GPL"); |