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	fbtft_par_dbg(DEBUG_SET_ADDR_WIN, par,
76		      "%s(xs=%d, ys=%d, xe=%d, ye=%d)\n", __func__, xs, ys, xe,
77		      ye);
78
79	write_reg(par, 0x75);
80	write_reg(par, 0x00);
81	write_reg(par, 0x3f);
82	write_reg(par, 0x15);
83	write_reg(par, 0x00);
84	write_reg(par, 0x7f);
85}
86
87static int blank(struct fbtft_par *par, bool on)
88{
89	fbtft_par_dbg(DEBUG_BLANK, par, "(%s=%s)\n",
90		      __func__, on ? "true" : "false");
91
92	if (on)
93		write_reg(par, 0xAE);
94	else
95		write_reg(par, 0xAF);
96	return 0;
97}
98
99/*
100 * Grayscale Lookup Table
101 * GS1 - GS15
102 * The "Gamma curve" contains the relative values between the entries
103 * in the Lookup table.
104 *
105 * 0 = Setting of GS1 < Setting of GS2 < Setting of GS3.....<
106 * Setting of GS14 < Setting of GS15
107 */
108static int set_gamma(struct fbtft_par *par, u32 *curves)
109{
110	int i;
111
112	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
113
114	for (i = 0; i < GAMMA_LEN; i++) {
115		if (i > 0 && curves[i] < 1) {
116			dev_err(par->info->device,
117				"Illegal value in Grayscale Lookup Table at index %d.\n"
118				"Must be greater than 0\n", i);
119			return -EINVAL;
120		}
121		if (curves[i] > 7) {
122			dev_err(par->info->device,
123				"Illegal value(s) in Grayscale Lookup Table.\n"
124				"At index=%d, the accumulated value has exceeded 7\n",
125				i);
126			return -EINVAL;
127		}
128	}
129	write_reg(par, 0xB8);
130	for (i = 0; i < 8; i++)
131		write_reg(par, (curves[i] & 0xFF));
132	return 0;
133}
134
135static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
136{
137	u16 *vmem16 = (u16 *)par->info->screen_buffer;
138	u8 *buf = par->txbuf.buf;
139	u8 n1;
140	u8 n2;
141	int y, x;
142	int ret;
143
144	for (x = 0; x < par->info->var.xres; x++) {
145		if (x % 2)
146			continue;
147		for (y = 0; y < par->info->var.yres; y++) {
148			n1 = rgb565_to_g16(vmem16[y * par->info->var.xres + x]);
149			n2 = rgb565_to_g16(vmem16
150					   [y * par->info->var.xres + x + 1]);
151			*buf = (n1 << 4) | n2;
152			buf++;
153		}
154	}
155
156	gpiod_set_value(par->gpio.dc, 1);
157
158	/* Write data */
159	ret = par->fbtftops.write(par, par->txbuf.buf,
160				par->info->var.xres * par->info->var.yres / 2);
161	if (ret < 0)
162		dev_err(par->info->device,
163			"%s: write failed and returned: %d\n", __func__, ret);
164
165	return ret;
166}
167
168static struct fbtft_display display = {
169	.regwidth = 8,
170	.width = WIDTH,
171	.height = HEIGHT,
172	.txbuflen = WIDTH * HEIGHT / 2,
173	.gamma_num = GAMMA_NUM,
174	.gamma_len = GAMMA_LEN,
175	.gamma = DEFAULT_GAMMA,
176	.fbtftops = {
177		.write_vmem = write_vmem,
178		.init_display = init_display,
179		.set_addr_win = set_addr_win,
180		.blank = blank,
181		.set_gamma = set_gamma,
182	},
183};
184
185FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display);
186
187MODULE_ALIAS("spi:" DRVNAME);
188MODULE_ALIAS("platform:" DRVNAME);
189MODULE_ALIAS("spi:ssd1325");
190MODULE_ALIAS("platform:ssd1325");
191
192MODULE_DESCRIPTION("SSD1325 OLED Driver");
193MODULE_AUTHOR("Alexey Mednyy");
194MODULE_LICENSE("GPL");
195