// SPDX-License-Identifier: GPL-2.0+
/*
 * FB driver for Two KS0108 LCD controllers in AGM1264K-FL display
 *
 * Copyright (C) 2014 ololoshka2871
 */

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

#include "fbtft.h"

/* Uncomment text line to use negative image on display */
/*#define NEGATIVE*/

#define WHITE           0xff
#define BLACK           0

#define DRVNAME         "fb_agm1264k-fl"
#define WIDTH           64
#define HEIGHT          64
#define TOTALWIDTH      (WIDTH * 2)      /* because 2 x ks0108 in one display */
#define FPS                     20

#define EPIN            gpio.wr
#define RS                      gpio.dc
#define RW                      gpio.aux[2]
#define CS0                     gpio.aux[0]
#define CS1                     gpio.aux[1]

/* diffusing error (Floyd-Steinberg) */
#define DIFFUSING_MATRIX_WIDTH  2
#define DIFFUSING_MATRIX_HEIGHT 2

static const signed char
diffusing_matrix[DIFFUSING_MATRIX_WIDTH][DIFFUSING_MATRIX_HEIGHT] = {
        {-1, 3},
        {3, 2},
};

static const unsigned char gamma_correction_table[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6,
6, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 11, 11, 11, 12, 12, 13,
13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21,
22, 22, 23, 23, 24, 25, 25, 26, 26, 27, 28, 28, 29, 30, 30, 31, 32,
33, 33, 34, 35, 35, 36, 37, 38, 39, 39, 40, 41, 42, 43, 43, 44, 45,
46, 47, 48, 49, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 81,
82, 83, 84, 85, 87, 88, 89, 90, 91, 93, 94, 95, 97, 98, 99, 100, 102,
103, 105, 106, 107, 109, 110, 111, 113, 114, 116, 117, 119, 120, 121,
123, 124, 126, 127, 129, 130, 132, 133, 135, 137, 138, 140, 141, 143,
145, 146, 148, 149, 151, 153, 154, 156, 158, 159, 161, 163, 165, 166,
168, 170, 172, 173, 175, 177, 179, 181, 182, 184, 186, 188, 190, 192,
194, 196, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, 219,
221, 223, 225, 227, 229, 231, 234, 236, 238, 240, 242, 244, 246, 248,
251, 253, 255
};

static int init_display(struct fbtft_par *par)
{
        u8 i;

        par->fbtftops.reset(par);

        for (i = 0; i < 2; ++i) {
                write_reg(par, i, 0x3f); /* display on */
                write_reg(par, i, 0x40); /* set x to 0 */
                write_reg(par, i, 0xb0); /* set page to 0 */
                write_reg(par, i, 0xc0); /* set start line to 0 */
        }

        return 0;
}

/* Check if all necessary GPIOS defined */
static int verify_gpios(struct fbtft_par *par)
{
        int i;

        dev_dbg(par->info->device,
                "%s()\n", __func__);

        if (!par->EPIN) {
                dev_err(par->info->device,
                        "Missing info about 'wr' (aka E) gpio. Aborting.\n");
                return -EINVAL;
        }
        for (i = 0; i < 8; ++i) {
                if (!par->gpio.db[i]) {
                        dev_err(par->info->device,
                                "Missing info about 'db[%i]' gpio. Aborting.\n",
                                i);
                        return -EINVAL;
                }
        }
        if (!par->CS0) {
                dev_err(par->info->device,
                        "Missing info about 'cs0' gpio. Aborting.\n");
                return -EINVAL;
        }
        if (!par->CS1) {
                dev_err(par->info->device,
                        "Missing info about 'cs1' gpio. Aborting.\n");
                return -EINVAL;
        }
        if (!par->RW) {
                dev_err(par->info->device,
                        "Missing info about 'rw' gpio. Aborting.\n");
                return -EINVAL;
        }

        return 0;
}

static unsigned long
request_gpios_match(struct fbtft_par *par, const struct fbtft_gpio *gpio)
{
        dev_dbg(par->info->device,
                "%s('%s')\n", __func__, gpio->name);

        if (strcasecmp(gpio->name, "wr") == 0) {
                /* left ks0108 E pin */
                par->EPIN = gpio->gpio;
                return GPIOD_OUT_LOW;
        } else if (strcasecmp(gpio->name, "cs0") == 0) {
                /* left ks0108 controller pin */
                par->CS0 = gpio->gpio;
                return GPIOD_OUT_HIGH;
        } else if (strcasecmp(gpio->name, "cs1") == 0) {
                /* right ks0108 controller pin */
                par->CS1 = gpio->gpio;
                return GPIOD_OUT_HIGH;
        }

        /* if write (rw = 0) e(1->0) perform write */
        /* if read (rw = 1) e(0->1) set data on D0-7*/
        else if (strcasecmp(gpio->name, "rw") == 0) {
                par->RW = gpio->gpio;
                return GPIOD_OUT_LOW;
        }

        return FBTFT_GPIO_NO_MATCH;
}

/* This function oses to enter commands
 * first byte - destination controller 0 or 1
 * following - commands
 */
static void write_reg8_bus8(struct fbtft_par *par, int len, ...)
{
        va_list args;
        int i, ret;
        u8 *buf = par->buf;

        if (unlikely(par->debug & DEBUG_WRITE_REGISTER)) {
                va_start(args, len);
                for (i = 0; i < len; i++)
                        buf[i] = (u8)va_arg(args, unsigned int);

                va_end(args);
                fbtft_par_dbg_hex(DEBUG_WRITE_REGISTER, par, par->info->device,
                                  u8, buf, len, "%s: ", __func__);
}

        va_start(args, len);

        *buf = (u8)va_arg(args, unsigned int);

        if (*buf > 1) {
                va_end(args);
                dev_err(par->info->device,
                        "Incorrect chip select request (%d)\n", *buf);
                return;
        }

        /* select chip */
        if (*buf) {
                /* cs1 */
                gpiod_set_value(par->CS0, 0);
                gpiod_set_value(par->CS1, 1);
        } else {
                /* cs0 */
                gpiod_set_value(par->CS0, 1);
                gpiod_set_value(par->CS1, 0);
        }

        gpiod_set_value(par->RS, 0); /* RS->0 (command mode) */
        len--;

        if (len) {
                i = len;
                while (i--)
                        *buf++ = (u8)va_arg(args, unsigned int);
                ret = par->fbtftops.write(par, par->buf, len * (sizeof(u8)));
                if (ret < 0) {
                        va_end(args);
                        dev_err(par->info->device,
                                "write() failed and returned %d\n", ret);
                        return;
                }
        }

        va_end(args);
}

static struct
{
        int xs, ys_page, xe, ye_page;
} addr_win;

/* save display writing zone */
static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
        addr_win.xs = xs;
        addr_win.ys_page = ys / 8;
        addr_win.xe = xe;
        addr_win.ye_page = ye / 8;
}

static void
construct_line_bitmap(struct fbtft_par *par, u8 *dest, signed short *src,
                      int xs, int xe, int y)
{
        int x, i;

        for (x = xs; x < xe; ++x) {
                u8 res = 0;

                for (i = 0; i < 8; i++)
                        if (src[(y * 8 + i) * par->info->var.xres + x])
                                res |= 1 << i;
#ifdef NEGATIVE
                *dest++ = res;
#else
                *dest++ = ~res;
#endif
        }
}

static void iterate_diffusion_matrix(u32 xres, u32 yres, int x,
                                     int y, signed short *convert_buf,
                                     signed short pixel, signed short error)
{
        u16 i, j;

        /* diffusion matrix row */
        for (i = 0; i < DIFFUSING_MATRIX_WIDTH; ++i)
                /* diffusion matrix column */
                for (j = 0; j < DIFFUSING_MATRIX_HEIGHT; ++j) {
                        signed short *write_pos;
                        signed char coeff;

                        /* skip pixels out of zone */
                        if (x + i < 0 || x + i >= xres || y + j >= yres)
                                continue;
                        write_pos = &convert_buf[(y + j) * xres + x + i];
                        coeff = diffusing_matrix[i][j];
                        if (-1 == coeff) {
                                /* pixel itself */
                                *write_pos = pixel;
                        } else {
                                signed short p = *write_pos + error * coeff;

                                if (p > WHITE)
                                        p = WHITE;
                                if (p < BLACK)
                                        p = BLACK;
                                *write_pos = p;
                        }
                }
}

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;
        int x, y;
        int ret = 0;

        /* buffer to convert RGB565 -> grayscale16 -> Dithered image 1bpp */
        signed short *convert_buf = kmalloc_objs(signed short,
                                                 par->info->var.xres * par->info->var.yres,
                                                 GFP_NOIO);

        if (!convert_buf)
                return -ENOMEM;

        /* converting to grayscale16 */
        for (x = 0; x < par->info->var.xres; ++x)
                for (y = 0; y < par->info->var.yres; ++y) {
                        u16 pixel = vmem16[y *  par->info->var.xres + x];
                        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) / 200;
                        if (pixel > 255)
                                pixel = 255;

                        /* gamma-correction by table */
                        convert_buf[y *  par->info->var.xres + x] =
                                (signed short)gamma_correction_table[pixel];
                }

        /* Image Dithering */
        for (x = 0; x < par->info->var.xres; ++x)
                for (y = 0; y < par->info->var.yres; ++y) {
                        signed short pixel =
                                convert_buf[y *  par->info->var.xres + x];
                        signed short error_b = pixel - BLACK;
                        signed short error_w = pixel - WHITE;
                        signed short error;

                        /* what color close? */
                        if (abs(error_b) >= abs(error_w)) {
                                /* white */
                                error = error_w;
                                pixel = 0xff;
                        } else {
                                /* black */
                                error = error_b;
                                pixel = 0;
                        }

                        error /= 8;

                        iterate_diffusion_matrix(par->info->var.xres,
                                                 par->info->var.yres,
                                                 x, y, convert_buf,
                                                 pixel, error);
                }

        /* 1 string = 2 pages */
        for (y = addr_win.ys_page; y <= addr_win.ye_page; ++y) {
                /* left half of display */
                if (addr_win.xs < par->info->var.xres / 2) {
                        construct_line_bitmap(par, buf, convert_buf,
                                              addr_win.xs,
                                              par->info->var.xres / 2, y);

                        len = par->info->var.xres / 2 - addr_win.xs;

                        /* select left side (sc0)
                         * set addr
                         */
                        write_reg(par, 0x00, BIT(6) | (u8)addr_win.xs);
                        write_reg(par, 0x00, (0x17 << 3) | (u8)y);

                        /* write bitmap */
                        gpiod_set_value(par->RS, 1); /* RS->1 (data mode) */
                        ret = par->fbtftops.write(par, buf, len);
                        if (ret < 0)
                                dev_err(par->info->device,
                                        "write failed and returned: %d\n",
                                        ret);
                }
                /* right half of display */
                if (addr_win.xe >= par->info->var.xres / 2) {
                        construct_line_bitmap(par, buf,
                                              convert_buf,
                                              par->info->var.xres / 2,
                                              addr_win.xe + 1, y);

                        len = addr_win.xe + 1 - par->info->var.xres / 2;

                        /* select right side (sc1)
                         * set addr
                         */
                        write_reg(par, 0x01, BIT(6));
                        write_reg(par, 0x01, (0x17 << 3) | (u8)y);

                        /* write bitmap */
                        gpiod_set_value(par->RS, 1); /* RS->1 (data mode) */
                        par->fbtftops.write(par, buf, len);
                        if (ret < 0)
                                dev_err(par->info->device,
                                        "write failed and returned: %d\n",
                                        ret);
                }
        }
        kfree(convert_buf);

        gpiod_set_value(par->CS0, 0);
        gpiod_set_value(par->CS1, 0);

        return ret;
}

static int write(struct fbtft_par *par, void *buf, size_t len)
{
        fbtft_par_dbg_hex(DEBUG_WRITE, par, par->info->device, u8, buf, len,
                          "%s(len=%zu): ", __func__, len);

        gpiod_set_value(par->RW, 0); /* set write mode */

        while (len--) {
                u8 i, data;

                data = *(u8 *)buf++;

                /* set data bus */
                for (i = 0; i < 8; ++i)
                        gpiod_set_value(par->gpio.db[i], data & (1 << i));
                /* set E */
                gpiod_set_value(par->EPIN, 0);
                udelay(5);
                /* unset E - write */
                gpiod_set_value(par->EPIN, 1);
                udelay(1);
        }

        return 0;
}

static struct fbtft_display display = {
        .regwidth = 8,
        .width = TOTALWIDTH,
        .height = HEIGHT,
        .fps = FPS,
        .fbtftops = {
                .init_display = init_display,
                .set_addr_win = set_addr_win,
                .verify_gpios = verify_gpios,
                .request_gpios_match = request_gpios_match,
                .write = write,
                .write_register = write_reg8_bus8,
                .write_vmem = write_vmem,
        },
};

FBTFT_REGISTER_DRIVER(DRVNAME, "displaytronic,fb_agm1264k-fl", &display);

MODULE_ALIAS("platform:" DRVNAME);

MODULE_DESCRIPTION("Two KS0108 LCD controllers in AGM1264K-FL display");
MODULE_AUTHOR("ololoshka2871");
MODULE_LICENSE("GPL");