drm/solomon: Add SSD130x OLED displays SPI support

	  I2C bus.

	  If M is selected the module will be called ssd130x-i2c.

config DRM_SSD130X_SPI

	tristate "DRM support for Solomon SSD130X OLED displays (SPI bus)"

	depends on DRM_SSD130X && SPI

	select REGMAP

	help

	  Say Y here if the SSD130x OLED display is connected via SPI bus.

	  If M is selected the module will be called ssd130x-spi.

obj-$(CONFIG_DRM_SSD130X)	+= ssd130x.o

obj-$(CONFIG_DRM_SSD130X_I2C)	+= ssd130x-i2c.o

obj-$(CONFIG_DRM_SSD130X_SPI)	+= ssd130x-spi.o

// SPDX-License-Identifier: GPL-2.0-only

/*

 * DRM driver for Solomon SSD130X OLED displays (SPI bus)

 *

 * Copyright 2022 Red Hat Inc.

 * Authors: Javier Martinez Canillas <javierm@redhat.com>

 */

#include <linux/spi/spi.h>

#include <linux/module.h>

#include "ssd130x.h"

#define DRIVER_NAME	"ssd130x-spi"

#define DRIVER_DESC	"DRM driver for Solomon SSD130X OLED displays (SPI)"

struct ssd130x_spi_transport {

	struct spi_device *spi;

	struct gpio_desc *dc;

};

static const struct regmap_config ssd130x_spi_regmap_config = {

	.reg_bits = 8,

	.val_bits = 8,

};

/*

 * The regmap bus .write handler, it is just a wrapper around spi_write()

 * but toggling the Data/Command control pin (D/C#). Since for 4-wire SPI

 * a D/C# pin is used, in contrast with I2C where a control byte is sent,

 * prior to every data byte, that contains a bit with the D/C# value.

 *

 * These control bytes are considered registers by the ssd130x core driver

 * and can be used by the ssd130x SPI driver to determine if the data sent

 * is for a command register or for the Graphic Display Data RAM (GDDRAM).

 */

static int ssd130x_spi_write(void *context, const void *data, size_t count)

{

	struct ssd130x_spi_transport *t = context;

	struct spi_device *spi = t->spi;

	const u8 *reg = data;

	if (*reg == SSD130X_COMMAND)

		gpiod_set_value_cansleep(t->dc, 0);

	if (*reg == SSD130X_DATA)

		gpiod_set_value_cansleep(t->dc, 1);

	/* Remove control byte since is not used in a 4-wire SPI interface */

	return spi_write(spi, reg + 1, count - 1);

}

/* The ssd130x driver does not read registers but regmap expects a .read */

static int ssd130x_spi_read(void *context, const void *reg, size_t reg_size,

			    void *val, size_t val_size)

{

	return -EOPNOTSUPP;

}

/*

 * A custom bus is needed due the special write that toggles a D/C# pin,

 * another option could be to just have a .reg_write() callback but that

 * will prevent to do data writes in bulk.

 *

 * Once the regmap API is extended to support defining a bulk write handler

 * in the struct regmap_config, this can be simplified and the bus dropped.

 */

static struct regmap_bus regmap_ssd130x_spi_bus = {

	.write = ssd130x_spi_write,

	.read = ssd130x_spi_read,

};

static int ssd130x_spi_probe(struct spi_device *spi)

{

	struct ssd130x_spi_transport *t;

	struct ssd130x_device *ssd130x;

	struct regmap *regmap;

	struct gpio_desc *dc;

	struct device *dev = &spi->dev;

	dc = devm_gpiod_get(dev, "dc", GPIOD_OUT_LOW);

	if (IS_ERR(dc))

		return dev_err_probe(dev, PTR_ERR(dc),

				     "Failed to get dc gpio\n");

	t = devm_kzalloc(dev, sizeof(*t), GFP_KERNEL);

	if (!t)

		return dev_err_probe(dev, -ENOMEM,

				     "Failed to allocate SPI transport data\n");

	t->spi = spi;

	t->dc = dc;

	regmap = devm_regmap_init(dev, &regmap_ssd130x_spi_bus, t,

				  &ssd130x_spi_regmap_config);

	if (IS_ERR(regmap))

		return PTR_ERR(regmap);

	ssd130x = ssd130x_probe(dev, regmap);

	if (IS_ERR(ssd130x))

		return PTR_ERR(ssd130x);

	spi_set_drvdata(spi, ssd130x);

	return 0;

}

static void ssd130x_spi_remove(struct spi_device *spi)

{

	struct ssd130x_device *ssd130x = spi_get_drvdata(spi);

	ssd130x_remove(ssd130x);

}

static void ssd130x_spi_shutdown(struct spi_device *spi)

{

	struct ssd130x_device *ssd130x = spi_get_drvdata(spi);

	ssd130x_shutdown(ssd130x);

}

static const struct of_device_id ssd130x_of_match[] = {

	{

		.compatible = "sinowealth,sh1106",

		.data = &ssd130x_variants[SH1106_ID],

	},

	{

		.compatible = "solomon,ssd1305",

		.data = &ssd130x_variants[SSD1305_ID],

	},

	{

		.compatible = "solomon,ssd1306",

		.data = &ssd130x_variants[SSD1306_ID],

	},

	{

		.compatible = "solomon,ssd1307",

		.data = &ssd130x_variants[SSD1307_ID],

	},

	{

		.compatible = "solomon,ssd1309",

		.data = &ssd130x_variants[SSD1309_ID],

	},

	{ /* sentinel */ }

};

MODULE_DEVICE_TABLE(of, ssd130x_of_match);

/*

 * The SPI core always reports a MODALIAS uevent of the form "spi:<dev>", even

 * if the device was registered via OF. This means that the module will not be

 * auto loaded, unless it contains an alias that matches the MODALIAS reported.

 *

 * To workaround this issue, add a SPI device ID table. Even when this should

 * not be needed for this driver to match the registered SPI devices.

 */

static const struct spi_device_id ssd130x_spi_table[] = {

	{ "sh1106",  SH1106_ID },

	{ "ssd1305", SSD1305_ID },

	{ "ssd1306", SSD1306_ID },

	{ "ssd1307", SSD1307_ID },

	{ "ssd1309", SSD1309_ID },

	{ /* sentinel */ }

};

MODULE_DEVICE_TABLE(spi, ssd130x_spi_table);

static struct spi_driver ssd130x_spi_driver = {

	.driver = {

		.name = DRIVER_NAME,

		.of_match_table = ssd130x_of_match,

	},

	.probe = ssd130x_spi_probe,

	.remove = ssd130x_spi_remove,

	.shutdown = ssd130x_spi_shutdown,

};

module_spi_driver(ssd130x_spi_driver);

MODULE_DESCRIPTION(DRIVER_DESC);

MODULE_AUTHOR("Javier Martinez Canillas <javierm@redhat.com>");

MODULE_LICENSE("GPL");

MODULE_IMPORT_NS(DRM_SSD130X);