fb_ssd1325.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * FB driver for the SSD1325 OLED Controller
  4 */
  5
  6#include <linux/module.h>
  7#include <linux/kernel.h>
  8#include <linux/init.h>
  9#include <linux/gpio/consumer.h>
 10#include <linux/delay.h>
 11
 12#include "fbtft.h"
 13
 14#define DRVNAME		"fb_ssd1325"
 15
 16#define WIDTH 128
 17#define HEIGHT 64
 18#define GAMMA_NUM   1
 19#define GAMMA_LEN   15
 20#define DEFAULT_GAMMA "7 1 1 1 1 2 2 3 3 4 4 5 5 6 6"
 21
 22/*
 23 * write_reg() caveat:
 24 *
 25 *    This doesn't work because D/C has to be LOW for both values:
 26 *      write_reg(par, val1, val2);
 27 *
 28 *    Do it like this:
 29 *      write_reg(par, val1);
 30 *      write_reg(par, val2);
 31 */
 32
 33/* Init sequence taken from the Adafruit SSD1306 Arduino library */
 34static int init_display(struct fbtft_par *par)
 35{
 36	par->fbtftops.reset(par);
 37
 38	write_reg(par, 0xb3);
 39	write_reg(par, 0xf0);
 40	write_reg(par, 0xae);
 41	write_reg(par, 0xa1);
 42	write_reg(par, 0x00);
 43	write_reg(par, 0xa8);
 44	write_reg(par, 0x3f);
 45	write_reg(par, 0xa0);
 46	write_reg(par, 0x45);
 47	write_reg(par, 0xa2);
 48	write_reg(par, 0x40);
 49	write_reg(par, 0x75);
 50	write_reg(par, 0x00);
 51	write_reg(par, 0x3f);
 52	write_reg(par, 0x15);
 53	write_reg(par, 0x00);
 54	write_reg(par, 0x7f);
 55	write_reg(par, 0xa4);
 56	write_reg(par, 0xaf);
 57
 58	return 0;
 59}
 60
 61static uint8_t rgb565_to_g16(u16 pixel)
 62{
 63	u16 b = pixel & 0x1f;
 64	u16 g = (pixel & (0x3f << 5)) >> 5;
 65	u16 r = (pixel & (0x1f << (5 + 6))) >> (5 + 6);
 66
 67	pixel = (299 * r + 587 * g + 114 * b) / 195;
 68	if (pixel > 255)
 69		pixel = 255;
 70	return (uint8_t)pixel / 16;
 71}
 72
 73static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
 74{
 75	write_reg(par, 0x75);
 76	write_reg(par, 0x00);
 77	write_reg(par, 0x3f);
 78	write_reg(par, 0x15);
 79	write_reg(par, 0x00);
 80	write_reg(par, 0x7f);
 81}
 82
 83static int blank(struct fbtft_par *par, bool on)
 84{
 85	if (on)
 86		write_reg(par, 0xAE);
 87	else
 88		write_reg(par, 0xAF);
 89	return 0;
 90}
 91
 92/*
 93 * Grayscale Lookup Table
 94 * GS1 - GS15
 95 * The "Gamma curve" contains the relative values between the entries
 96 * in the Lookup table.
 97 *
 98 * 0 = Setting of GS1 < Setting of GS2 < Setting of GS3.....<
 99 * Setting of GS14 < Setting of GS15
100 */
101static int set_gamma(struct fbtft_par *par, u32 *curves)
102{
103	int i;
104
105	for (i = 0; i < GAMMA_LEN; i++) {
106		if (i > 0 && curves[i] < 1) {
107			dev_err(par->info->device,
108				"Illegal value in Grayscale Lookup Table at index %d.\n"
109				"Must be greater than 0\n", i);
110			return -EINVAL;
111		}
112		if (curves[i] > 7) {
113			dev_err(par->info->device,
114				"Illegal value(s) in Grayscale Lookup Table.\n"
115				"At index=%d, the accumulated value has exceeded 7\n",
116				i);
117			return -EINVAL;
118		}
119	}
120	write_reg(par, 0xB8);
121	for (i = 0; i < 8; i++)
122		write_reg(par, (curves[i] & 0xFF));
123	return 0;
124}
125
126static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
127{
128	u16 *vmem16 = (u16 *)par->info->screen_buffer;
129	u8 *buf = par->txbuf.buf;
130	u8 n1;
131	u8 n2;
132	int y, x;
133	int ret;
134
135	for (x = 0; x < par->info->var.xres; x++) {
136		if (x % 2)
137			continue;
138		for (y = 0; y < par->info->var.yres; y++) {
139			n1 = rgb565_to_g16(vmem16[y * par->info->var.xres + x]);
140			n2 = rgb565_to_g16(vmem16
141					   [y * par->info->var.xres + x + 1]);
142			*buf = (n1 << 4) | n2;
143			buf++;
144		}
145	}
146
147	gpiod_set_value(par->gpio.dc, 1);
148
149	/* Write data */
150	ret = par->fbtftops.write(par, par->txbuf.buf,
151				par->info->var.xres * par->info->var.yres / 2);
152	if (ret < 0)
153		dev_err(par->info->device,
154			"%s: write failed and returned: %d\n", __func__, ret);
155
156	return ret;
157}
158
159static struct fbtft_display display = {
160	.regwidth = 8,
161	.width = WIDTH,
162	.height = HEIGHT,
163	.txbuflen = WIDTH * HEIGHT / 2,
164	.gamma_num = GAMMA_NUM,
165	.gamma_len = GAMMA_LEN,
166	.gamma = DEFAULT_GAMMA,
167	.fbtftops = {
168		.write_vmem = write_vmem,
169		.init_display = init_display,
170		.set_addr_win = set_addr_win,
171		.blank = blank,
172		.set_gamma = set_gamma,
173	},
174};
175
176FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display);
177
178MODULE_ALIAS("spi:" DRVNAME);
179MODULE_ALIAS("platform:" DRVNAME);
180MODULE_ALIAS("spi:ssd1325");
181MODULE_ALIAS("platform:ssd1325");
182
183MODULE_DESCRIPTION("SSD1325 OLED Driver");
184MODULE_AUTHOR("Alexey Mednyy");
185MODULE_LICENSE("GPL");