1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * DRM driver for Solomon SSD130X OLED displays (SPI bus)
  4 *
  5 * Copyright 2022 Red Hat Inc.
  6 * Authors: Javier Martinez Canillas <javierm@redhat.com>
  7 */
  8#include <linux/spi/spi.h>
  9#include <linux/module.h>
 10
 11#include "ssd130x.h"
 12
 13#define DRIVER_NAME	"ssd130x-spi"
 14#define DRIVER_DESC	"DRM driver for Solomon SSD130X OLED displays (SPI)"
 15
 16struct ssd130x_spi_transport {
 17	struct spi_device *spi;
 18	struct gpio_desc *dc;
 19};
 20
 21/*
 22 * The regmap bus .write handler, it is just a wrapper around spi_write()
 23 * but toggling the Data/Command control pin (D/C#). Since for 4-wire SPI
 24 * a D/C# pin is used, in contrast with I2C where a control byte is sent,
 25 * prior to every data byte, that contains a bit with the D/C# value.
 26 *
 27 * These control bytes are considered registers by the ssd130x core driver
 28 * and can be used by the ssd130x SPI driver to determine if the data sent
 29 * is for a command register or for the Graphic Display Data RAM (GDDRAM).
 30 */
 31static int ssd130x_spi_write(void *context, const void *data, size_t count)
 32{
 33	struct ssd130x_spi_transport *t = context;
 34	struct spi_device *spi = t->spi;
 35	const u8 *reg = data;
 36
 37	if (*reg == SSD130X_COMMAND)
 38		gpiod_set_value_cansleep(t->dc, 0);
 39
 40	if (*reg == SSD130X_DATA)
 41		gpiod_set_value_cansleep(t->dc, 1);
 42
 43	/* Remove control byte since is not used in a 4-wire SPI interface */
 44	return spi_write(spi, reg + 1, count - 1);
 45}
 46
 47/* The ssd130x driver does not read registers but regmap expects a .read */
 48static int ssd130x_spi_read(void *context, const void *reg, size_t reg_size,
 49			    void *val, size_t val_size)
 50{
 51	return -EOPNOTSUPP;
 52}
 53
 54static const struct regmap_config ssd130x_spi_regmap_config = {
 55	.reg_bits = 8,
 56	.val_bits = 8,
 57	.write = ssd130x_spi_write,
 58	.read = ssd130x_spi_read,
 59	.can_multi_write = true,
 60};
 61
 62static int ssd130x_spi_probe(struct spi_device *spi)
 63{
 64	struct ssd130x_spi_transport *t;
 65	struct ssd130x_device *ssd130x;
 66	struct regmap *regmap;
 67	struct gpio_desc *dc;
 68	struct device *dev = &spi->dev;
 69
 70	dc = devm_gpiod_get(dev, "dc", GPIOD_OUT_LOW);
 71	if (IS_ERR(dc))
 72		return dev_err_probe(dev, PTR_ERR(dc),
 73				     "Failed to get dc gpio\n");
 74
 75	t = devm_kzalloc(dev, sizeof(*t), GFP_KERNEL);
 76	if (!t)
 77		return dev_err_probe(dev, -ENOMEM,
 78				     "Failed to allocate SPI transport data\n");
 79
 80	t->spi = spi;
 81	t->dc = dc;
 82
 83	regmap = devm_regmap_init(dev, NULL, t, &ssd130x_spi_regmap_config);
 84	if (IS_ERR(regmap))
 85		return PTR_ERR(regmap);
 86
 87	ssd130x = ssd130x_probe(dev, regmap);
 88	if (IS_ERR(ssd130x))
 89		return PTR_ERR(ssd130x);
 90
 91	spi_set_drvdata(spi, ssd130x);
 92
 93	return 0;
 94}
 95
 96static void ssd130x_spi_remove(struct spi_device *spi)
 97{
 98	struct ssd130x_device *ssd130x = spi_get_drvdata(spi);
 99
100	ssd130x_remove(ssd130x);
101}
102
103static void ssd130x_spi_shutdown(struct spi_device *spi)
104{
105	struct ssd130x_device *ssd130x = spi_get_drvdata(spi);
106
107	ssd130x_shutdown(ssd130x);
108}
109
110static const struct of_device_id ssd130x_of_match[] = {
111	{
112		.compatible = "sinowealth,sh1106",
113		.data = &ssd130x_variants[SH1106_ID],
114	},
115	{
116		.compatible = "solomon,ssd1305",
117		.data = &ssd130x_variants[SSD1305_ID],
118	},
119	{
120		.compatible = "solomon,ssd1306",
121		.data = &ssd130x_variants[SSD1306_ID],
122	},
123	{
124		.compatible = "solomon,ssd1307",
125		.data = &ssd130x_variants[SSD1307_ID],
126	},
127	{
128		.compatible = "solomon,ssd1309",
129		.data = &ssd130x_variants[SSD1309_ID],
130	},
131	{ /* sentinel */ }
132};
133MODULE_DEVICE_TABLE(of, ssd130x_of_match);
134
135#if IS_MODULE(CONFIG_DRM_SSD130X_SPI)
136/*
137 * The SPI core always reports a MODALIAS uevent of the form "spi:<dev>", even
138 * if the device was registered via OF. This means that the module will not be
139 * auto loaded, unless it contains an alias that matches the MODALIAS reported.
140 *
141 * To workaround this issue, add a SPI device ID table. Even when this should
142 * not be needed for this driver to match the registered SPI devices.
143 */
144static const struct spi_device_id ssd130x_spi_table[] = {
145	{ "sh1106",  SH1106_ID },
146	{ "ssd1305", SSD1305_ID },
147	{ "ssd1306", SSD1306_ID },
148	{ "ssd1307", SSD1307_ID },
149	{ "ssd1309", SSD1309_ID },
150	{ /* sentinel */ }
151};
152MODULE_DEVICE_TABLE(spi, ssd130x_spi_table);
153#endif
154
155static struct spi_driver ssd130x_spi_driver = {
156	.driver = {
157		.name = DRIVER_NAME,
158		.of_match_table = ssd130x_of_match,
159	},
160	.probe = ssd130x_spi_probe,
161	.remove = ssd130x_spi_remove,
162	.shutdown = ssd130x_spi_shutdown,
163};
164module_spi_driver(ssd130x_spi_driver);
165
166MODULE_DESCRIPTION(DRIVER_DESC);
167MODULE_AUTHOR("Javier Martinez Canillas <javierm@redhat.com>");
168MODULE_LICENSE("GPL");
169MODULE_IMPORT_NS(DRM_SSD130X);