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// 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, ®map_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);
#if IS_MODULE(CONFIG_DRM_SSD130X_SPI)
/*
* 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);
#endif
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);
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