// SPDX-License-Identifier: GPL-2.0+
/*
 * FB driver for the SH1106 OLED Controller
 * Based on the SSD1306 driver by Noralf Tronnes
 *
 * Copyright (C) 2017 Heiner Kallweit
 */

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

#include "fbtft.h"

#define DRVNAME         "fb_sh1106"
#define WIDTH           128
#define HEIGHT          64

/* Init sequence based on the Adafruit SSD1306 Arduino library */
static int init_display(struct fbtft_par *par)
{
        if (!par->info->var.xres || par->info->var.xres > WIDTH ||
            !par->info->var.yres || par->info->var.yres > HEIGHT ||
            par->info->var.yres % 8) {
                dev_err(par->info->device, "Invalid screen size\n");
                return -EINVAL;
        }

        if (par->info->var.rotate) {
                dev_err(par->info->device, "Display rotation not supported\n");
                return -EINVAL;
        }

        par->fbtftops.reset(par);

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

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

        /* Set Multiplex Ratio */
        write_reg(par, 0xA8, par->info->var.yres - 1);

        /* Set Display Offset */
        write_reg(par, 0xD3, 0x00);

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

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

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

        /* Set VCOMH Deselect Level */
        write_reg(par, 0xDB, 0x40);

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

        msleep(150);

        return 0;
}

static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
}

static int blank(struct fbtft_par *par, bool on)
{
        write_reg(par, on ? 0xAE : 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, 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;
        int page, page_start, page_end, x, i, ret;
        u8 *buf = par->txbuf.buf;

        /* offset refers to vmem with 2 bytes element size */
        page_start = offset / (8 * 2 * xres);
        page_end = DIV_ROUND_UP(offset + len, 8 * 2 * xres);

        for (page = page_start; page < page_end; page++) {
                /* set page and set column to 2 because of vidmem width 132 */
                write_reg(par, 0xb0 | page, 0x00 | 2, 0x10 | 0);

                memset(buf, 0, xres);
                for (x = 0; x < xres; x++)
                        for (i = 0; i < 8; i++)
                                if (vmem16[(page * 8 + i) * xres + x])
                                        buf[x] |= BIT(i);

                /* Write data */
                ret = fbtft_write_buf_dc(par, buf, xres, 1);
                if (ret < 0)
                        return ret;
        }

        return 0;
}

static void write_register(struct fbtft_par *par, int len, ...)
{
        va_list args;
        int i;

        va_start(args, len);

        for (i = 0; i < len; i++)
                par->buf[i] = va_arg(args, unsigned int);

        /* keep DC low for all command bytes to transfer */
        fbtft_write_buf_dc(par, par->buf, len, 0);

        va_end(args);
}

static struct fbtft_display display = {
        .regwidth = 8,
        .width = WIDTH,
        .height = HEIGHT,
        .txbuflen = WIDTH,
        .gamma_num = 1,
        .gamma_len = 1,
        /* set default contrast to 0xcd = 80% */
        .gamma = "cd",
        .fbtftops = {
                .write_vmem = write_vmem,
                .write_register = write_register,
                .init_display = init_display,
                .set_addr_win = set_addr_win,
                .blank = blank,
                .set_gamma = set_gamma,
        },
};

FBTFT_REGISTER_SPI_DRIVER(DRVNAME, "sinowealth", "sh1106", &display);

MODULE_DESCRIPTION("SH1106 OLED Driver");
MODULE_AUTHOR("Heiner Kallweit");
MODULE_LICENSE("GPL");