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 */
init_display(struct fbtft_par * par)34 static 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
rgb565_to_g16(u16 pixel)61 static 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
set_addr_win(struct fbtft_par * par,int xs,int ys,int xe,int ye)73 static 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
blank(struct fbtft_par * par,bool on)83 static 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 */
set_gamma(struct fbtft_par * par,u32 * curves)101 static 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
write_vmem(struct fbtft_par * par,size_t offset,size_t len)126 static 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
159 static 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
176 FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display);
177
178 MODULE_ALIAS("spi:" DRVNAME);
179 MODULE_ALIAS("platform:" DRVNAME);
180 MODULE_ALIAS("spi:ssd1325");
181 MODULE_ALIAS("platform:ssd1325");
182
183 MODULE_DESCRIPTION("SSD1325 OLED Driver");
184 MODULE_AUTHOR("Alexey Mednyy");
185 MODULE_LICENSE("GPL");
186