fb_pcd8544.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * FB driver for the PCD8544 LCD Controller
  4 *
  5 * The display is monochrome and the video memory is RGB565.
  6 * Any pixel value except 0 turns the pixel on.
  7 *
  8 * Copyright (C) 2013 Noralf Tronnes
  9 */
 10
 11#include <linux/module.h>
 12#include <linux/kernel.h>
 13#include <linux/init.h>
 14#include <linux/gpio/consumer.h>
 15#include <linux/spi/spi.h>
 16#include <linux/delay.h>
 17
 18#include "fbtft.h"
 19
 20#define DRVNAME	       "fb_pcd8544"
 21#define WIDTH          84
 22#define HEIGHT         48
 23#define TXBUFLEN       (84 * 6)
 24#define DEFAULT_GAMMA  "40" /* gamma controls the contrast in this driver */
 25
 26static unsigned int tc;
 27module_param(tc, uint, 0000);
 28MODULE_PARM_DESC(tc, "TC[1:0] Temperature coefficient: 0-3 (default: 0)");
 29
 30static unsigned int bs = 4;
 31module_param(bs, uint, 0000);
 32MODULE_PARM_DESC(bs, "BS[2:0] Bias voltage level: 0-7 (default: 4)");
 33
 34static int init_display(struct fbtft_par *par)
 35{
 36	par->fbtftops.reset(par);
 37
 38	/* Function set
 39	 *
 40	 * 5:1  1
 41	 * 2:0  PD - Powerdown control: chip is active
 42	 * 1:0  V  - Entry mode: horizontal addressing
 43	 * 0:1  H  - Extended instruction set control: extended
 44	 */
 45	write_reg(par, 0x21);
 46
 47	/* H=1 Temperature control
 48	 *
 49	 * 2:1  1
 50	 * 1:x  TC1 - Temperature Coefficient: 0x10
 51	 * 0:x  TC0
 52	 */
 53	write_reg(par, 0x04 | (tc & 0x3));
 54
 55	/* H=1 Bias system
 56	 *
 57	 * 4:1  1
 58	 * 3:0  0
 59	 * 2:x  BS2 - Bias System
 60	 * 1:x  BS1
 61	 * 0:x  BS0
 62	 */
 63	write_reg(par, 0x10 | (bs & 0x7));
 64
 65	/* Function set
 66	 *
 67	 * 5:1  1
 68	 * 2:0  PD - Powerdown control: chip is active
 69	 * 1:1  V  - Entry mode: vertical addressing
 70	 * 0:0  H  - Extended instruction set control: basic
 71	 */
 72	write_reg(par, 0x22);
 73
 74	/* H=0 Display control
 75	 *
 76	 * 3:1  1
 77	 * 2:1  D  - DE: 10=normal mode
 78	 * 1:0  0
 79	 * 0:0  E
 80	 */
 81	write_reg(par, 0x08 | 4);
 82
 83	return 0;
 84}
 85
 86static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
 87{
 88	/* H=0 Set X address of RAM
 89	 *
 90	 * 7:1  1
 91	 * 6-0: X[6:0] - 0x00
 92	 */
 93	write_reg(par, 0x80);
 94
 95	/* H=0 Set Y address of RAM
 96	 *
 97	 * 7:0  0
 98	 * 6:1  1
 99	 * 2-0: Y[2:0] - 0x0
100	 */
101	write_reg(par, 0x40);
102}
103
104static int write_vmem(struct fbtft_par *par, size_t offset, size_t len)
105{
106	u16 *vmem16 = (u16 *)par->info->screen_buffer;
107	u8 *buf = par->txbuf.buf;
108	int x, y, i;
109	int ret = 0;
110
111	for (x = 0; x < 84; x++) {
112		for (y = 0; y < 6; y++) {
113			*buf = 0x00;
114			for (i = 0; i < 8; i++)
115				*buf |= (vmem16[(y * 8 + i) * 84 + x] ?
116					 1 : 0) << i;
117			buf++;
118		}
119	}
120
121	/* Write data */
122	gpiod_set_value(par->gpio.dc, 1);
123	ret = par->fbtftops.write(par, par->txbuf.buf, 6 * 84);
124	if (ret < 0)
125		dev_err(par->info->device, "write failed and returned: %d\n",
126			ret);
127
128	return ret;
129}
130
131static int set_gamma(struct fbtft_par *par, u32 *curves)
132{
133	/* apply mask */
134	curves[0] &= 0x7F;
135
136	write_reg(par, 0x23); /* turn on extended instruction set */
137	write_reg(par, 0x80 | curves[0]);
138	write_reg(par, 0x22); /* turn off extended instruction set */
139
140	return 0;
141}
142
143static struct fbtft_display display = {
144	.regwidth = 8,
145	.width = WIDTH,
146	.height = HEIGHT,
147	.txbuflen = TXBUFLEN,
148	.gamma_num = 1,
149	.gamma_len = 1,
150	.gamma = DEFAULT_GAMMA,
151	.fbtftops = {
152		.init_display = init_display,
153		.set_addr_win = set_addr_win,
154		.write_vmem = write_vmem,
155		.set_gamma = set_gamma,
156	},
157	.backlight = 1,
158};
159
160FBTFT_REGISTER_DRIVER(DRVNAME, "philips,pcd8544", &display);
161
162MODULE_ALIAS("spi:" DRVNAME);
163MODULE_ALIAS("spi:pcd8544");
164
165MODULE_DESCRIPTION("FB driver for the PCD8544 LCD Controller");
166MODULE_AUTHOR("Noralf Tronnes");
167MODULE_LICENSE("GPL");