linux/drivers/staging/fbtft/fb_ssd1325.c
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   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 */
  34static 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
  63static 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
  75static 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
  89static 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 */
 110static 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
 137static 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
 170static 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
 187FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display);
 188
 189MODULE_ALIAS("spi:" DRVNAME);
 190MODULE_ALIAS("platform:" DRVNAME);
 191MODULE_ALIAS("spi:ssd1325");
 192MODULE_ALIAS("platform:ssd1325");
 193
 194MODULE_DESCRIPTION("SSD1325 OLED Driver");
 195MODULE_AUTHOR("Alexey Mednyy");
 196MODULE_LICENSE("GPL");
 197