fb_pcd8544.c

/*
 * FB driver for the PCD8544 LCD Controller
 *
 * The display is monochrome and the video memory is RGB565.
 * Any pixel value except 0 turns the pixel on.
 *
 * Copyright (C) 2013 Noralf Tronnes
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

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

#include "fbtft.h"

#define DRVNAME	       "fb_pcd8544"
#define WIDTH          84
#define HEIGHT         48
#define TXBUFLEN       84*6
#define DEFAULT_GAMMA  "40" /* gamma is used to control contrast in this driver */

static unsigned tc = 0;
module_param(tc, uint, 0);
MODULE_PARM_DESC(tc, "TC[1:0] Temperature coefficient: 0-3 (default: 0)");

static unsigned bs = 4;
module_param(bs, uint, 0);
MODULE_PARM_DESC(bs, "BS[2:0] Bias voltage level: 0-7 (default: 4)");


static int init_display(struct fbtft_par *par)
{
	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);

	par->fbtftops.reset(par);

	/* Function set */
	write_reg(par, 0x21); /* 5:1  1
	                         2:0  PD - Powerdown control: chip is active
							 1:0  V  - Entry mode: horizontal addressing
							 0:1  H  - Extended instruction set control: extended
						  */

	/* H=1 Temperature control */
	write_reg(par, 0x04 | (tc & 0x3)); /* 
	                         2:1  1
	                         1:x  TC1 - Temperature Coefficient: 0x10
							 0:x  TC0
						  */

	/* H=1 Bias system */
	write_reg(par, 0x10 | (bs & 0x7)); /* 
	                         4:1  1
	                         3:0  0
							 2:x  BS2 - Bias System
							 1:x  BS1
							 0:x  BS0
	                      */

	/* Function set */
	write_reg(par, 0x22); /* 5:1  1
	                         2:0  PD - Powerdown control: chip is active
							 1:1  V  - Entry mode: vertical addressing
							 0:0  H  - Extended instruction set control: basic
						  */

	/* H=0 Display control */
	write_reg(par, 0x08 | 4); /* 
	                         3:1  1
	                         2:1  D  - DE: 10=normal mode
							 1:0  0
							 0:0  E
						  */

	return 0;
}

static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
{
	fbtft_par_dbg(DEBUG_SET_ADDR_WIN, par, "%s(xs=%d, ys=%d, xe=%d, ye=%d)\n", __func__, xs, ys, xe, ye);

	/* H=0 Set X address of RAM */
	write_reg(par, 0x80); /* 7:1  1
	                         6-0: X[6:0] - 0x00
	                      */

	/* H=0 Set Y address of RAM */
	write_reg(par, 0x40); /* 7:0  0
	                         6:1  1
	                         2-0: Y[2:0] - 0x0
	                      */
}

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

	fbtft_par_dbg(DEBUG_WRITE_VMEM, par, "%s()\n", __func__);

	for (x=0;x<84;x++) {
		for (y=0;y<6;y++) {
			*buf = 0x00;
			for (i=0;i<8;i++) {
				*buf |= (vmem16[(y*8+i)*84+x] ? 1 : 0) << i;
			}
			buf++;
		}
	}

	/* Write data */
	gpio_set_value(par->gpio.dc, 1);
	ret = par->fbtftops.write(par, par->txbuf.buf, 6*84);
	if (ret < 0)
		dev_err(par->info->device, "%s: write failed and returned: %d\n", __func__, ret);

	return ret;
}

static int set_gamma(struct fbtft_par *par, unsigned long *curves)
{
	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);

	/* apply mask */
	curves[0] &= 0x7F;

	write_reg(par, 0x23); /* turn on extended instruction set */
	write_reg(par, 0x80 | curves[0]);
	write_reg(par, 0x22); /* turn off extended instruction set */

	return 0;
}


static struct fbtft_display display = {
	.regwidth = 8,
	.width = WIDTH,
	.height = HEIGHT,
	.txbuflen = TXBUFLEN,
	.gamma_num = 1,
	.gamma_len = 1,
	.gamma = DEFAULT_GAMMA,
	.fbtftops = {
		.init_display = init_display,
		.set_addr_win = set_addr_win,
		.write_vmem = write_vmem,
		.set_gamma = set_gamma,
	},
	.backlight = 1,
};
FBTFT_REGISTER_DRIVER(DRVNAME, &display);

MODULE_ALIAS("spi:" DRVNAME);

MODULE_DESCRIPTION("FB driver for the PCD8544 LCD Controller");
MODULE_AUTHOR("Noralf Tronnes");
MODULE_LICENSE("GPL");