// 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");