// SPDX-License-Identifier: GPL-2.0+
/*
 * FB driver for the SSD1306 OLED Controller
 *
 * Copyright (C) 2013 Noralf Tronnes
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/gpio/consumer.h>
#include <linux/delay.h>

#include "fbtft.h"

#define DRVNAME         "fb_ssd1306"
#define WIDTH           128
#define HEIGHT          64

/*
 * 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);

        if (par->gamma.curves[0] == 0) {
                mutex_lock(&par->gamma.lock);
                if (par->info->var.yres == 64)
                        par->gamma.curves[0] = 0xCF;
                else
                        par->gamma.curves[0] = 0x8F;
                mutex_unlock(&par->gamma.lock);
        }

        /* Set Display OFF */
        write_reg(par, 0xAE);

        /* Set Display Clock Divide Ratio/ Oscillator Frequency */
        write_reg(par, 0xD5);
        write_reg(par, 0x80);

        /* Set Multiplex Ratio */
        write_reg(par, 0xA8);
        if (par->info->var.yres == 64)
                write_reg(par, 0x3F);
        else if (par->info->var.yres == 48)
                write_reg(par, 0x2F);
        else
                write_reg(par, 0x1F);

        /* Set Display Offset */
        write_reg(par, 0xD3);
        write_reg(par, 0x0);

        /* Set Display Start Line */
        write_reg(par, 0x40 | 0x0);

        /* Charge Pump Setting */
        write_reg(par, 0x8D);
        /* A[2] = 1b, Enable charge pump during display on */
        write_reg(par, 0x14);

        /* Set Memory Addressing Mode */
        write_reg(par, 0x20);
        /* Vertical addressing mode  */
        write_reg(par, 0x01);

        /* Set Segment Re-map */
        /* column address 127 is mapped to SEG0 */
        write_reg(par, 0xA0 | 0x1);

        /* Set COM Output Scan Direction */
        /* remapped mode. Scan from COM[N-1] to COM0 */
        write_reg(par, 0xC8);

        /* Set COM Pins Hardware Configuration */
        write_reg(par, 0xDA);
        if (par->info->var.yres == 64)
                /* A[4]=1b, Alternative COM pin configuration */
                write_reg(par, 0x12);
        else if (par->info->var.yres == 48)
                /* A[4]=1b, Alternative COM pin configuration */
                write_reg(par, 0x12);
        else
                /* A[4]=0b, Sequential COM pin configuration */
                write_reg(par, 0x02);

        /* Set Pre-charge Period */
        write_reg(par, 0xD9);
        write_reg(par, 0xF1);

        /* Set VCOMH Deselect Level */
        write_reg(par, 0xDB);
        /* according to the datasheet, this value is out of bounds */
        write_reg(par, 0x40);

        /* Entire Display ON */
        /* Resume to RAM content display. Output follows RAM content */
        write_reg(par, 0xA4);

        /* Set Normal Display
         * 0 in RAM: OFF in display panel
         * 1 in RAM: ON in display panel
         */
        write_reg(par, 0xA6);

        /* Set Display ON */
        write_reg(par, 0xAF);

        return 0;
}

static void set_addr_win_64x48(struct fbtft_par *par)
{
        /* Set Column Address */
        write_reg(par, 0x21);
        write_reg(par, 0x20);
        write_reg(par, 0x5F);

        /* Set Page Address */
        write_reg(par, 0x22);
        write_reg(par, 0x0);
        write_reg(par, 0x5);
}

static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
        /* Set Lower Column Start Address for Page Addressing Mode */
        write_reg(par, 0x00 | 0x0);
        /* Set Higher Column Start Address for Page Addressing Mode */
        write_reg(par, 0x10 | 0x0);
        /* Set Display Start Line */
        write_reg(par, 0x40 | 0x0);

        if (par->info->var.xres == 64 && par->info->var.yres == 48)
                set_addr_win_64x48(par);
}

static int blank(struct fbtft_par *par, bool on)
{
        if (on)
                write_reg(par, 0xAE);
        else
                write_reg(par, 0xAF);
        return 0;
}

/* Gamma is used to control Contrast */
static int set_gamma(struct fbtft_par *par, u32 *curves)
{
        /* apply mask */
        curves[0] &= 0xFF;

        /* Set Contrast Control for BANK0 */
        write_reg(par, 0x81);
        write_reg(par, curves[0]);

        return 0;
}

static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
{
        u16 *vmem16 = (u16 *)par->info->screen_buffer;
        u32 xres = par->info->var.xres;
        u32 yres = par->info->var.yres;
        u8 *buf = par->txbuf.buf;
        int x, y, i;
        int ret = 0;

        for (x = 0; x < xres; x++) {
                for (y = 0; y < yres / 8; y++) {
                        *buf = 0x00;
                        for (i = 0; i < 8; i++)
                                if (vmem16[(y * 8 + i) * xres + x])
                                        *buf |= BIT(i);
                        buf++;
                }
        }

        /* Write data */
        gpiod_set_value(par->gpio.dc, 1);
        ret = par->fbtftops.write(par, par->txbuf.buf, xres * yres / 8);
        if (ret < 0)
                dev_err(par->info->device, "write failed and returned: %d\n",
                        ret);

        return ret;
}

static struct fbtft_display display = {
        .regwidth = 8,
        .width = WIDTH,
        .height = HEIGHT,
        .gamma_num = 1,
        .gamma_len = 1,
        .gamma = "00",
        .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,ssd1306", &display);

MODULE_ALIAS("spi:" DRVNAME);
MODULE_ALIAS("platform:" DRVNAME);
MODULE_ALIAS("spi:ssd1306");
MODULE_ALIAS("platform:ssd1306");

MODULE_DESCRIPTION("SSD1306 OLED Driver");
MODULE_AUTHOR("Noralf Tronnes");
MODULE_LICENSE("GPL");