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.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 */ 34 static int init_display(struct fbtft_par *par) 35 { 36 par->fbtftops.reset(par); 37 38 gpio_set_value(par->gpio.cs, 0); 39 40 write_reg(par, 0xb3); 41 write_reg(par, 0xf0); 42 write_reg(par, 0xae); 43 write_reg(par, 0xa1); 44 write_reg(par, 0x00); 45 write_reg(par, 0xa8); 46 write_reg(par, 0x3f); 47 write_reg(par, 0xa0); 48 write_reg(par, 0x45); 49 write_reg(par, 0xa2); 50 write_reg(par, 0x40); 51 write_reg(par, 0x75); 52 write_reg(par, 0x00); 53 write_reg(par, 0x3f); 54 write_reg(par, 0x15); 55 write_reg(par, 0x00); 56 write_reg(par, 0x7f); 57 write_reg(par, 0xa4); 58 write_reg(par, 0xaf); 59 60 return 0; 61 } 62 63 static uint8_t rgb565_to_g16(u16 pixel) 64 { 65 u16 b = pixel & 0x1f; 66 u16 g = (pixel & (0x3f << 5)) >> 5; 67 u16 r = (pixel & (0x1f << (5 + 6))) >> (5 + 6); 68 69 pixel = (299 * r + 587 * g + 114 * b) / 195; 70 if (pixel > 255) 71 pixel = 255; 72 return (uint8_t)pixel / 16; 73 } 74 75 static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye) 76 { 77 fbtft_par_dbg(DEBUG_SET_ADDR_WIN, par, 78 "%s(xs=%d, ys=%d, xe=%d, ye=%d)\n", __func__, xs, ys, xe, 79 ye); 80 81 write_reg(par, 0x75); 82 write_reg(par, 0x00); 83 write_reg(par, 0x3f); 84 write_reg(par, 0x15); 85 write_reg(par, 0x00); 86 write_reg(par, 0x7f); 87 } 88 89 static int blank(struct fbtft_par *par, bool on) 90 { 91 fbtft_par_dbg(DEBUG_BLANK, par, "(%s=%s)\n", 92 __func__, on ? "true" : "false"); 93 94 if (on) 95 write_reg(par, 0xAE); 96 else 97 write_reg(par, 0xAF); 98 return 0; 99 } 100 101 /* 102 * Grayscale Lookup Table 103 * GS1 - GS15 104 * The "Gamma curve" contains the relative values between the entries 105 * in the Lookup table. 106 * 107 * 0 = Setting of GS1 < Setting of GS2 < Setting of GS3.....< 108 * Setting of GS14 < Setting of GS15 109 */ 110 static int set_gamma(struct fbtft_par *par, u32 *curves) 111 { 112 int i; 113 114 fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__); 115 116 for (i = 0; i < GAMMA_LEN; i++) { 117 if (i > 0 && curves[i] < 1) { 118 dev_err(par->info->device, 119 "Illegal value in Grayscale Lookup Table at index %d.\n" 120 "Must be greater than 0\n", i); 121 return -EINVAL; 122 } 123 if (curves[i] > 7) { 124 dev_err(par->info->device, 125 "Illegal value(s) in Grayscale Lookup Table.\n" 126 "At index=%d, the accumulated value has exceeded 7\n", 127 i); 128 return -EINVAL; 129 } 130 } 131 write_reg(par, 0xB8); 132 for (i = 0; i < 8; i++) 133 write_reg(par, (curves[i] & 0xFF)); 134 return 0; 135 } 136 137 static int write_vmem(struct fbtft_par *par, size_t offset, size_t len) 138 { 139 u16 *vmem16 = (u16 *)par->info->screen_buffer; 140 u8 *buf = par->txbuf.buf; 141 u8 n1; 142 u8 n2; 143 int y, x; 144 int ret; 145 146 for (x = 0; x < par->info->var.xres; x++) { 147 if (x % 2) 148 continue; 149 for (y = 0; y < par->info->var.yres; y++) { 150 n1 = rgb565_to_g16(vmem16[y * par->info->var.xres + x]); 151 n2 = rgb565_to_g16(vmem16 152 [y * par->info->var.xres + x + 1]); 153 *buf = (n1 << 4) | n2; 154 buf++; 155 } 156 } 157 158 gpio_set_value(par->gpio.dc, 1); 159 160 /* Write data */ 161 ret = par->fbtftops.write(par, par->txbuf.buf, 162 par->info->var.xres * par->info->var.yres / 2); 163 if (ret < 0) 164 dev_err(par->info->device, 165 "%s: write failed and returned: %d\n", __func__, ret); 166 167 return ret; 168 } 169 170 static struct fbtft_display display = { 171 .regwidth = 8, 172 .width = WIDTH, 173 .height = HEIGHT, 174 .txbuflen = WIDTH * HEIGHT / 2, 175 .gamma_num = GAMMA_NUM, 176 .gamma_len = GAMMA_LEN, 177 .gamma = DEFAULT_GAMMA, 178 .fbtftops = { 179 .write_vmem = write_vmem, 180 .init_display = init_display, 181 .set_addr_win = set_addr_win, 182 .blank = blank, 183 .set_gamma = set_gamma, 184 }, 185 }; 186 187 FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display); 188 189 MODULE_ALIAS("spi:" DRVNAME); 190 MODULE_ALIAS("platform:" DRVNAME); 191 MODULE_ALIAS("spi:ssd1325"); 192 MODULE_ALIAS("platform:ssd1325"); 193 194 MODULE_DESCRIPTION("SSD1325 OLED Driver"); 195 MODULE_AUTHOR("Alexey Mednyy"); 196 MODULE_LICENSE("GPL"); 197