drm/solomon/ssd130x-spi.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * DRM driver for Solomon SSD130X OLED displays (SPI bus)
0004  *
0005  * Copyright 2022 Red Hat Inc.
0006  * Authors: Javier Martinez Canillas <javierm@redhat.com>
0007  */
0008 #include <linux/spi/spi.h>
0009 #include <linux/module.h>
0010
0011 #include "ssd130x.h"
0012
0013 #define DRIVER_NAME "ssd130x-spi"
0014 #define DRIVER_DESC "DRM driver for Solomon SSD130X OLED displays (SPI)"
0015
0016 struct ssd130x_spi_transport {
0017     struct spi_device *spi;
0018     struct gpio_desc *dc;
0019 };
0020
0021 static const struct regmap_config ssd130x_spi_regmap_config = {
0022     .reg_bits = 8,
0023     .val_bits = 8,
0024 };
0025
0026 /*
0027  * The regmap bus .write handler, it is just a wrapper around spi_write()
0028  * but toggling the Data/Command control pin (D/C#). Since for 4-wire SPI
0029  * a D/C# pin is used, in contrast with I2C where a control byte is sent,
0030  * prior to every data byte, that contains a bit with the D/C# value.
0031  *
0032  * These control bytes are considered registers by the ssd130x core driver
0033  * and can be used by the ssd130x SPI driver to determine if the data sent
0034  * is for a command register or for the Graphic Display Data RAM (GDDRAM).
0035  */
0036 static int ssd130x_spi_write(void *context, const void *data, size_t count)
0037 {
0038     struct ssd130x_spi_transport *t = context;
0039     struct spi_device *spi = t->spi;
0040     const u8 *reg = data;
0041
0042     if (*reg == SSD130X_COMMAND)
0043         gpiod_set_value_cansleep(t->dc, 0);
0044
0045     if (*reg == SSD130X_DATA)
0046         gpiod_set_value_cansleep(t->dc, 1);
0047
0048     /* Remove control byte since is not used in a 4-wire SPI interface */
0049     return spi_write(spi, reg + 1, count - 1);
0050 }
0051
0052 /* The ssd130x driver does not read registers but regmap expects a .read */
0053 static int ssd130x_spi_read(void *context, const void *reg, size_t reg_size,
0054                 void *val, size_t val_size)
0055 {
0056     return -EOPNOTSUPP;
0057 }
0058
0059 /*
0060  * A custom bus is needed due the special write that toggles a D/C# pin,
0061  * another option could be to just have a .reg_write() callback but that
0062  * will prevent to do data writes in bulk.
0063  *
0064  * Once the regmap API is extended to support defining a bulk write handler
0065  * in the struct regmap_config, this can be simplified and the bus dropped.
0066  */
0067 static struct regmap_bus regmap_ssd130x_spi_bus = {
0068     .write = ssd130x_spi_write,
0069     .read = ssd130x_spi_read,
0070 };
0071
0072 static int ssd130x_spi_probe(struct spi_device *spi)
0073 {
0074     struct ssd130x_spi_transport *t;
0075     struct ssd130x_device *ssd130x;
0076     struct regmap *regmap;
0077     struct gpio_desc *dc;
0078     struct device *dev = &spi->dev;
0079
0080     dc = devm_gpiod_get(dev, "dc", GPIOD_OUT_LOW);
0081     if (IS_ERR(dc))
0082         return dev_err_probe(dev, PTR_ERR(dc),
0083                      "Failed to get dc gpio\n");
0084
0085     t = devm_kzalloc(dev, sizeof(*t), GFP_KERNEL);
0086     if (!t)
0087         return dev_err_probe(dev, -ENOMEM,
0088                      "Failed to allocate SPI transport data\n");
0089
0090     t->spi = spi;
0091     t->dc = dc;
0092
0093     regmap = devm_regmap_init(dev, &regmap_ssd130x_spi_bus, t,
0094                   &ssd130x_spi_regmap_config);
0095     if (IS_ERR(regmap))
0096         return PTR_ERR(regmap);
0097
0098     ssd130x = ssd130x_probe(dev, regmap);
0099     if (IS_ERR(ssd130x))
0100         return PTR_ERR(ssd130x);
0101
0102     spi_set_drvdata(spi, ssd130x);
0103
0104     return 0;
0105 }
0106
0107 static void ssd130x_spi_remove(struct spi_device *spi)
0108 {
0109     struct ssd130x_device *ssd130x = spi_get_drvdata(spi);
0110
0111     ssd130x_remove(ssd130x);
0112 }
0113
0114 static void ssd130x_spi_shutdown(struct spi_device *spi)
0115 {
0116     struct ssd130x_device *ssd130x = spi_get_drvdata(spi);
0117
0118     ssd130x_shutdown(ssd130x);
0119 }
0120
0121 static const struct of_device_id ssd130x_of_match[] = {
0122     {
0123         .compatible = "sinowealth,sh1106",
0124         .data = &ssd130x_variants[SH1106_ID],
0125     },
0126     {
0127         .compatible = "solomon,ssd1305",
0128         .data = &ssd130x_variants[SSD1305_ID],
0129     },
0130     {
0131         .compatible = "solomon,ssd1306",
0132         .data = &ssd130x_variants[SSD1306_ID],
0133     },
0134     {
0135         .compatible = "solomon,ssd1307",
0136         .data = &ssd130x_variants[SSD1307_ID],
0137     },
0138     {
0139         .compatible = "solomon,ssd1309",
0140         .data = &ssd130x_variants[SSD1309_ID],
0141     },
0142     { /* sentinel */ }
0143 };
0144 MODULE_DEVICE_TABLE(of, ssd130x_of_match);
0145
0146 #if IS_MODULE(CONFIG_DRM_SSD130X_SPI)
0147 /*
0148  * The SPI core always reports a MODALIAS uevent of the form "spi:<dev>", even
0149  * if the device was registered via OF. This means that the module will not be
0150  * auto loaded, unless it contains an alias that matches the MODALIAS reported.
0151  *
0152  * To workaround this issue, add a SPI device ID table. Even when this should
0153  * not be needed for this driver to match the registered SPI devices.
0154  */
0155 static const struct spi_device_id ssd130x_spi_table[] = {
0156     { "sh1106",  SH1106_ID },
0157     { "ssd1305", SSD1305_ID },
0158     { "ssd1306", SSD1306_ID },
0159     { "ssd1307", SSD1307_ID },
0160     { "ssd1309", SSD1309_ID },
0161     { /* sentinel */ }
0162 };
0163 MODULE_DEVICE_TABLE(spi, ssd130x_spi_table);
0164 #endif
0165
0166 static struct spi_driver ssd130x_spi_driver = {
0167     .driver = {
0168         .name = DRIVER_NAME,
0169         .of_match_table = ssd130x_of_match,
0170     },
0171     .probe = ssd130x_spi_probe,
0172     .remove = ssd130x_spi_remove,
0173     .shutdown = ssd130x_spi_shutdown,
0174 };
0175 module_spi_driver(ssd130x_spi_driver);
0176
0177 MODULE_DESCRIPTION(DRIVER_DESC);
0178 MODULE_AUTHOR("Javier Martinez Canillas <javierm@redhat.com>");
0179 MODULE_LICENSE("GPL");
0180 MODULE_IMPORT_NS(DRM_SSD130X);