// SPDX-License-Identifier: GPL-2.0
/*
 *    Filename: cfag12864b.c
 *     Version: 0.1.0
 * Description: cfag12864b LCD driver
 *     Depends: ks0108
 *
 *      Author: Copyright (C) Miguel Ojeda <ojeda@kernel.org>
 *        Date: 2006-10-31
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/cdev.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/jiffies.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
#include <linux/ks0108.h>
#include <linux/cfag12864b.h>


#define CFAG12864B_NAME "cfag12864b"

/*
 * Module Parameters
 */

static unsigned int cfag12864b_rate = CONFIG_CFAG12864B_RATE;
module_param(cfag12864b_rate, uint, 0444);
MODULE_PARM_DESC(cfag12864b_rate,
        "Refresh rate (hertz)");

/*
 * cfag12864b Commands
 *
 *      E = Enable signal
 *              Every time E switch from low to high,
 *              cfag12864b/ks0108 reads the command/data.
 *
 *      CS1 = First ks0108controller.
 *              If high, the first ks0108 controller receives commands/data.
 *
 *      CS2 = Second ks0108 controller
 *              If high, the second ks0108 controller receives commands/data.
 *
 *      DI = Data/Instruction
 *              If low, cfag12864b will expect commands.
 *              If high, cfag12864b will expect data.
 *
 */

#define bit(n) (((unsigned char)1)<<(n))

#define CFAG12864B_BIT_E        (0)
#define CFAG12864B_BIT_CS1      (2)
#define CFAG12864B_BIT_CS2      (1)
#define CFAG12864B_BIT_DI       (3)

static unsigned char cfag12864b_state;

static void cfag12864b_set(void)
{
        ks0108_writecontrol(cfag12864b_state);
}

static void cfag12864b_setbit(unsigned char state, unsigned char n)
{
        if (state)
                cfag12864b_state |= bit(n);
        else
                cfag12864b_state &= ~bit(n);
}

static void cfag12864b_e(unsigned char state)
{
        cfag12864b_setbit(state, CFAG12864B_BIT_E);
        cfag12864b_set();
}

static void cfag12864b_cs1(unsigned char state)
{
        cfag12864b_setbit(state, CFAG12864B_BIT_CS1);
}

static void cfag12864b_cs2(unsigned char state)
{
        cfag12864b_setbit(state, CFAG12864B_BIT_CS2);
}

static void cfag12864b_di(unsigned char state)
{
        cfag12864b_setbit(state, CFAG12864B_BIT_DI);
}

static void cfag12864b_setcontrollers(unsigned char first,
        unsigned char second)
{
        if (first)
                cfag12864b_cs1(0);
        else
                cfag12864b_cs1(1);

        if (second)
                cfag12864b_cs2(0);
        else
                cfag12864b_cs2(1);
}

static void cfag12864b_controller(unsigned char which)
{
        if (which == 0)
                cfag12864b_setcontrollers(1, 0);
        else if (which == 1)
                cfag12864b_setcontrollers(0, 1);
}

static void cfag12864b_displaystate(unsigned char state)
{
        cfag12864b_di(0);
        cfag12864b_e(1);
        ks0108_displaystate(state);
        cfag12864b_e(0);
}

static void cfag12864b_address(unsigned char address)
{
        cfag12864b_di(0);
        cfag12864b_e(1);
        ks0108_address(address);
        cfag12864b_e(0);
}

static void cfag12864b_page(unsigned char page)
{
        cfag12864b_di(0);
        cfag12864b_e(1);
        ks0108_page(page);
        cfag12864b_e(0);
}

static void cfag12864b_startline(unsigned char startline)
{
        cfag12864b_di(0);
        cfag12864b_e(1);
        ks0108_startline(startline);
        cfag12864b_e(0);
}

static void cfag12864b_writebyte(unsigned char byte)
{
        cfag12864b_di(1);
        cfag12864b_e(1);
        ks0108_writedata(byte);
        cfag12864b_e(0);
}

static void cfag12864b_nop(void)
{
        cfag12864b_startline(0);
}

/*
 * cfag12864b Internal Commands
 */

static void cfag12864b_on(void)
{
        cfag12864b_setcontrollers(1, 1);
        cfag12864b_displaystate(1);
}

static void cfag12864b_off(void)
{
        cfag12864b_setcontrollers(1, 1);
        cfag12864b_displaystate(0);
}

static void cfag12864b_clear(void)
{
        unsigned char i, j;

        cfag12864b_setcontrollers(1, 1);
        for (i = 0; i < CFAG12864B_PAGES; i++) {
                cfag12864b_page(i);
                cfag12864b_address(0);
                for (j = 0; j < CFAG12864B_ADDRESSES; j++)
                        cfag12864b_writebyte(0);
        }
}

/*
 * Update work
 */

unsigned char *cfag12864b_buffer;
static unsigned char *cfag12864b_cache;
static DEFINE_MUTEX(cfag12864b_mutex);
static unsigned char cfag12864b_updating;
static void cfag12864b_update(struct work_struct *delayed_work);
static struct workqueue_struct *cfag12864b_workqueue;
static DECLARE_DELAYED_WORK(cfag12864b_work, cfag12864b_update);

static void cfag12864b_queue(void)
{
        queue_delayed_work(cfag12864b_workqueue, &cfag12864b_work,
                HZ / cfag12864b_rate);
}

unsigned char cfag12864b_enable(void)
{
        unsigned char ret;

        mutex_lock(&cfag12864b_mutex);

        if (!cfag12864b_updating) {
                cfag12864b_updating = 1;
                cfag12864b_queue();
                ret = 0;
        } else
                ret = 1;

        mutex_unlock(&cfag12864b_mutex);

        return ret;
}

void cfag12864b_disable(void)
{
        mutex_lock(&cfag12864b_mutex);

        if (cfag12864b_updating) {
                cfag12864b_updating = 0;
                cancel_delayed_work(&cfag12864b_work);
                flush_workqueue(cfag12864b_workqueue);
        }

        mutex_unlock(&cfag12864b_mutex);
}

static void cfag12864b_update(struct work_struct *work)
{
        unsigned char c;
        unsigned short i, j, k, b;

        if (memcmp(cfag12864b_cache, cfag12864b_buffer, CFAG12864B_SIZE)) {
                for (i = 0; i < CFAG12864B_CONTROLLERS; i++) {
                        cfag12864b_controller(i);
                        cfag12864b_nop();
                        for (j = 0; j < CFAG12864B_PAGES; j++) {
                                cfag12864b_page(j);
                                cfag12864b_nop();
                                cfag12864b_address(0);
                                cfag12864b_nop();
                                for (k = 0; k < CFAG12864B_ADDRESSES; k++) {
                                        for (c = 0, b = 0; b < 8; b++)
                                                if (cfag12864b_buffer
                                                        [i * CFAG12864B_ADDRESSES / 8
                                                        + k / 8 + (j * 8 + b) *
                                                        CFAG12864B_WIDTH / 8]
                                                        & bit(k % 8))
                                                        c |= bit(b);
                                        cfag12864b_writebyte(c);
                                }
                        }
                }

                memcpy(cfag12864b_cache, cfag12864b_buffer, CFAG12864B_SIZE);
        }

        if (cfag12864b_updating)
                cfag12864b_queue();
}

/*
 * cfag12864b Exported Symbols
 */

EXPORT_SYMBOL_GPL(cfag12864b_buffer);
EXPORT_SYMBOL_GPL(cfag12864b_enable);
EXPORT_SYMBOL_GPL(cfag12864b_disable);

/*
 * Is the module inited?
 */

static unsigned char cfag12864b_inited;
unsigned char cfag12864b_isinited(void)
{
        return cfag12864b_inited;
}
EXPORT_SYMBOL_GPL(cfag12864b_isinited);

/*
 * Module Init & Exit
 */

static int __init cfag12864b_init(void)
{
        int ret = -EINVAL;

        /* ks0108_init() must be called first */
        if (!ks0108_isinited()) {
                printk(KERN_ERR CFAG12864B_NAME ": ERROR: "
                        "ks0108 is not initialized\n");
                goto none;
        }
        BUILD_BUG_ON(PAGE_SIZE < CFAG12864B_SIZE);

        cfag12864b_buffer = (unsigned char *) get_zeroed_page(GFP_KERNEL);
        if (cfag12864b_buffer == NULL) {
                printk(KERN_ERR CFAG12864B_NAME ": ERROR: "
                        "can't get a free page\n");
                ret = -ENOMEM;
                goto none;
        }

        cfag12864b_cache = kmalloc(CFAG12864B_SIZE,
                                   GFP_KERNEL);
        if (cfag12864b_cache == NULL) {
                printk(KERN_ERR CFAG12864B_NAME ": ERROR: "
                        "can't alloc cache buffer (%i bytes)\n",
                        CFAG12864B_SIZE);
                ret = -ENOMEM;
                goto bufferalloced;
        }

        cfag12864b_workqueue = create_singlethread_workqueue(CFAG12864B_NAME);
        if (cfag12864b_workqueue == NULL)
                goto cachealloced;

        cfag12864b_clear();
        cfag12864b_on();

        cfag12864b_inited = 1;
        return 0;

cachealloced:
        kfree(cfag12864b_cache);

bufferalloced:
        free_page((unsigned long) cfag12864b_buffer);

none:
        return ret;
}

static void __exit cfag12864b_exit(void)
{
        cfag12864b_disable();
        cfag12864b_off();
        destroy_workqueue(cfag12864b_workqueue);
        kfree(cfag12864b_cache);
        free_page((unsigned long) cfag12864b_buffer);
}

module_init(cfag12864b_init);
module_exit(cfag12864b_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Miguel Ojeda <ojeda@kernel.org>");
MODULE_DESCRIPTION("cfag12864b LCD driver");