text: /*
   * FB driver for the SSD1325 OLED Controller
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/gpio.h>
  #include <linux/delay.h>
  
  #include "fbtft.h"
  
  #define DRVNAME		"fb_ssd1325"
  
  #define WIDTH 128
  #define HEIGHT 64
  #define GAMMA_NUM   1
  #define GAMMA_LEN   15
  #define DEFAULT_GAMMA "7 1 1 1 1 2 2 3 3 4 4 5 5 6 6"
  
  /*
   * write_reg() caveat:
   *
   *    This doesn't work because D/C has to be LOW for both values:
   *      write_reg(par, val1, val2);
   *
   *    Do it like this:
   *      write_reg(par, val1);
   *      write_reg(par, val2);
   */
  
  /* Init sequence taken from the Adafruit SSD1306 Arduino library */
  static int init_display(struct fbtft_par *par)
  {
  	par->fbtftops.reset(par);
  
  	gpio_set_value(par->gpio.cs, 0);
  
  	write_reg(par, 0xb3);
  	write_reg(par, 0xf0);
  	write_reg(par, 0xae);
  	write_reg(par, 0xa1);
  	write_reg(par, 0x00);
  	write_reg(par, 0xa8);
  	write_reg(par, 0x3f);
  	write_reg(par, 0xa0);
  	write_reg(par, 0x45);
  	write_reg(par, 0xa2);
  	write_reg(par, 0x40);
  	write_reg(par, 0x75);
  	write_reg(par, 0x00);
  	write_reg(par, 0x3f);
  	write_reg(par, 0x15);
  	write_reg(par, 0x00);
  	write_reg(par, 0x7f);
  	write_reg(par, 0xa4);
  	write_reg(par, 0xaf);
  
  	return 0;
  }
  
  static uint8_t rgb565_to_g16(u16 pixel)
  {
  	u16 b = pixel & 0x1f;
  	u16 g = (pixel & (0x3f << 5)) >> 5;
  	u16 r = (pixel & (0x1f << (5 + 6))) >> (5 + 6);
  
  	pixel = (299 * r + 587 * g + 114 * b) / 195;
  	if (pixel > 255)
  		pixel = 255;
  	return (uint8_t)pixel / 16;
  }
  
  static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
  {
  	fbtft_par_dbg(DEBUG_SET_ADDR_WIN, par,
  		      "%s(xs=%d, ys=%d, xe=%d, ye=%d)\n", __func__, xs, ys, xe,
  		      ye);
  
  	write_reg(par, 0x75);
  	write_reg(par, 0x00);
  	write_reg(par, 0x3f);
  	write_reg(par, 0x15);
  	write_reg(par, 0x00);
  	write_reg(par, 0x7f);
  }
  
  static int blank(struct fbtft_par *par, bool on)
  {
  	fbtft_par_dbg(DEBUG_BLANK, par, "%s(blank=%s)\n",
  		      __func__, on ? "true" : "false");
  
  	if (on)
  		write_reg(par, 0xAE);
  	else
  		write_reg(par, 0xAF);
  	return 0;
  }
  
  /*
   * Grayscale Lookup Table
   * GS1 - GS15
   * The "Gamma curve" contains the relative values between the entries
   * in the Lookup table.
   *
   * 0 = Setting of GS1 < Setting of GS2 < Setting of GS3.....<
   * Setting of GS14 < Setting of GS15
   */
  static int set_gamma(struct fbtft_par *par, u32 *curves)
  {
  	int i;
  
  	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
  
  	for (i = 0; i < GAMMA_LEN; i++) {
  		if (i > 0 && curves[i] < 1) {
  			dev_err(par->info->device,
  				"Illegal value in Grayscale Lookup Table at index %d.\n"
  				"Must be greater than 0\n", i);
  			return -EINVAL;
  		}
  		if (curves[i] > 7) {
  			dev_err(par->info->device,
  				"Illegal value(s) in Grayscale Lookup Table.\n"
  				"At index=%d, the accumulated value has exceeded 7\n",
  				i);
  			return -EINVAL;
  		}
  	}
  	write_reg(par, 0xB8);
  	for (i = 0; i < 8; i++)
  		write_reg(par, (curves[i] & 0xFF));
  	return 0;
  }
  
  static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
  {
  	u16 *vmem16 = (u16 *)par->info->screen_buffer;
  	u8 *buf = par->txbuf.buf;
  	u8 n1;
  	u8 n2;
  	int y, x;
  	int ret;
  
  	for (x = 0; x < par->info->var.xres; x++) {
  		if (x % 2)
  			continue;
  		for (y = 0; y < par->info->var.yres; y++) {
  			n1 = rgb565_to_g16(vmem16[y * par->info->var.xres + x]);
  			n2 = rgb565_to_g16(vmem16
  					   [y * par->info->var.xres + x + 1]);
  			*buf = (n1 << 4) | n2;
  			buf++;
  		}
  	}
  
  	gpio_set_value(par->gpio.dc, 1);
  
  	/* Write data */
  	ret = par->fbtftops.write(par, par->txbuf.buf,
  				par->info->var.xres * par->info->var.yres / 2);
  	if (ret < 0)
  		dev_err(par->info->device,
  			"%s: write failed and returned: %d\n", __func__, ret);
  
  	return ret;
  }
  
  static struct fbtft_display display = {
  	.regwidth = 8,
  	.width = WIDTH,
  	.height = HEIGHT,
  	.txbuflen = WIDTH * HEIGHT / 2,
  	.gamma_num = GAMMA_NUM,
  	.gamma_len = GAMMA_LEN,
  	.gamma = DEFAULT_GAMMA,
  	.fbtftops = {
  		.write_vmem = write_vmem,
  		.init_display = init_display,
  		.set_addr_win = set_addr_win,
  		.blank = blank,
  		.set_gamma = set_gamma,
  	},
  };
  
  FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1325", &display);
  
  MODULE_ALIAS("spi:" DRVNAME);
  MODULE_ALIAS("platform:" DRVNAME);
  MODULE_ALIAS("spi:ssd1325");
  MODULE_ALIAS("platform:ssd1325");
  
  MODULE_DESCRIPTION("SSD1325 OLED Driver");
  MODULE_AUTHOR("Alexey Mednyy");
  MODULE_LICENSE("GPL");
  