gpio-spear-spics.c

/*
 * SPEAr platform SPI chipselect abstraction over gpiolib
 *
 * Copyright (C) 2012 ST Microelectronics
 * Shiraz Hashim <shiraz.linux.kernel@gmail.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 = gpiochip_get_data(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 = gpiochip_get_data(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 = gpiochip_get_data(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;

	spics = devm_kzalloc(&pdev->dev, sizeof(*spics), GFP_KERNEL);
	if (!spics)
		return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	spics->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(spics->base))
		return PTR_ERR(spics->base);

	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.parent = &pdev->dev;
	spics->chip.owner = THIS_MODULE;
	spics->last_off = -1;

	ret = devm_gpiochip_add_data(&pdev->dev, &spics->chip, spics);
	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 = {
		.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.linux.kernel@gmail.com>");
MODULE_DESCRIPTION("STMicroelectronics SPEAr SPI Chip Select Abstraction");
MODULE_LICENSE("GPL");