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 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
blank(struct fbtft_par * par,bool on)87 static 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 */
set_gamma(struct fbtft_par * par,u32 * curves)108 static 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
write_vmem(struct fbtft_par * par,size_t offset,size_t len)135 static 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
168 static 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
185 FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display);
186
187 MODULE_ALIAS("spi:" DRVNAME);
188 MODULE_ALIAS("platform:" DRVNAME);
189 MODULE_ALIAS("spi:ssd1325");
190 MODULE_ALIAS("platform:ssd1325");
191
192 MODULE_DESCRIPTION("SSD1325 OLED Driver");
193 MODULE_AUTHOR("Alexey Mednyy");
194 MODULE_LICENSE("GPL");
195