aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/misc/arm-charlcd.c
blob: 1256a4bf1c04aca6465bcdde05158ade90c7881e (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
/*
 * Driver for the on-board character LCD found on some ARM reference boards
 * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it
 * http://en.wikipedia.org/wiki/HD44780_Character_LCD
 * Currently it will just display the text "ARM Linux" and the linux version
 *
 * License terms: GNU General Public License (GPL) version 2
 * Author: Linus Walleij <triad@df.lth.se>
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <generated/utsrelease.h>

#define DRIVERNAME "arm-charlcd"
#define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))

/* Offsets to registers */
#define CHAR_COM	0x00U
#define CHAR_DAT	0x04U
#define CHAR_RD		0x08U
#define CHAR_RAW	0x0CU
#define CHAR_MASK	0x10U
#define CHAR_STAT	0x14U

#define CHAR_RAW_CLEAR	0x00000000U
#define CHAR_RAW_VALID	0x00000100U

/* Hitachi HD44780 display commands */
#define HD_CLEAR			0x01U
#define HD_HOME				0x02U
#define HD_ENTRYMODE			0x04U
#define HD_ENTRYMODE_INCREMENT		0x02U
#define HD_ENTRYMODE_SHIFT		0x01U
#define HD_DISPCTRL			0x08U
#define HD_DISPCTRL_ON			0x04U
#define HD_DISPCTRL_CURSOR_ON		0x02U
#define HD_DISPCTRL_CURSOR_BLINK	0x01U
#define HD_CRSR_SHIFT			0x10U
#define HD_CRSR_SHIFT_DISPLAY		0x08U
#define HD_CRSR_SHIFT_DISPLAY_RIGHT	0x04U
#define HD_FUNCSET			0x20U
#define HD_FUNCSET_8BIT			0x10U
#define HD_FUNCSET_2_LINES		0x08U
#define HD_FUNCSET_FONT_5X10		0x04U
#define HD_SET_CGRAM			0x40U
#define HD_SET_DDRAM			0x80U
#define HD_BUSY_FLAG			0x80U

/**
 * @dev: a pointer back to containing device
 * @phybase: the offset to the controller in physical memory
 * @physize: the size of the physical page
 * @virtbase: the offset to the controller in virtual memory
 * @irq: reserved interrupt number
 * @complete: completion structure for the last LCD command
 */
struct charlcd {
	struct device *dev;
	u32 phybase;
	u32 physize;
	void __iomem *virtbase;
	int irq;
	struct completion complete;
	struct delayed_work init_work;
};

static irqreturn_t charlcd_interrupt(int irq, void *data)
{
	struct charlcd *lcd = data;
	u8 status;

	status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
	/* Clear IRQ */
	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
	if (status)
		complete(&lcd->complete);
	else
		dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status);
	return IRQ_HANDLED;
}


static void charlcd_wait_complete_irq(struct charlcd *lcd)
{
	int ret;

	ret = wait_for_completion_interruptible_timeout(&lcd->complete,
							CHARLCD_TIMEOUT);
	/* Disable IRQ after completion */
	writel(0x00, lcd->virtbase + CHAR_MASK);

	if (ret < 0) {
		dev_err(lcd->dev,
			"wait_for_completion_interruptible_timeout() "
			"returned %d waiting for ready\n", ret);
		return;
	}

	if (ret == 0) {
		dev_err(lcd->dev, "charlcd controller timed out "
			"waiting for ready\n");
		return;
	}
}

static u8 charlcd_4bit_read_char(struct charlcd *lcd)
{
	u8 data;
	u32 val;
	int i;

	/* If we can, use an IRQ to wait for the data, else poll */
	if (lcd->irq >= 0)
		charlcd_wait_complete_irq(lcd);
	else {
		i = 0;
		val = 0;
		while (!(val & CHAR_RAW_VALID) && i < 10) {
			udelay(100);
			val = readl(lcd->virtbase + CHAR_RAW);
			i++;
		}

		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
	}
	msleep(1);

	/* Read the 4 high bits of the data */
	data = readl(lcd->virtbase + CHAR_RD) & 0xf0;

	/*
	 * The second read for the low bits does not trigger an IRQ
	 * so in this case we have to poll for the 4 lower bits
	 */
	i = 0;
	val = 0;
	while (!(val & CHAR_RAW_VALID) && i < 10) {
		udelay(100);
		val = readl(lcd->virtbase + CHAR_RAW);
		i++;
	}
	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
	msleep(1);

	/* Read the 4 low bits of the data */
	data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;

	return data;
}

static bool charlcd_4bit_read_bf(struct charlcd *lcd)
{
	if (lcd->irq >= 0) {
		/*
		 * If we'll use IRQs to wait for the busyflag, clear any
		 * pending flag and enable IRQ
		 */
		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
		init_completion(&lcd->complete);
		writel(0x01, lcd->virtbase + CHAR_MASK);
	}
	readl(lcd->virtbase + CHAR_COM);
	return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false;
}

static void charlcd_4bit_wait_busy(struct charlcd *lcd)
{
	int retries = 50;

	udelay(100);
	while (charlcd_4bit_read_bf(lcd) && retries)
		retries--;
	if (!retries)
		dev_err(lcd->dev, "timeout waiting for busyflag\n");
}

static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
{
	u32 cmdlo = (cmd << 4) & 0xf0;
	u32 cmdhi = (cmd & 0xf0);

	writel(cmdhi, lcd->virtbase + CHAR_COM);
	udelay(10);
	writel(cmdlo, lcd->virtbase + CHAR_COM);
	charlcd_4bit_wait_busy(lcd);
}

static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
{
	u32 chlo = (ch << 4) & 0xf0;
	u32 chhi = (ch & 0xf0);

	writel(chhi, lcd->virtbase + CHAR_DAT);
	udelay(10);
	writel(chlo, lcd->virtbase + CHAR_DAT);
	charlcd_4bit_wait_busy(lcd);
}

static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
{
	u8 offset;
	int i;

	/*
	 * We support line 0, 1
	 * Line 1 runs from 0x00..0x27
	 * Line 2 runs from 0x28..0x4f
	 */
	if (line == 0)
		offset = 0;
	else if (line == 1)
		offset = 0x28;
	else
		return;

	/* Set offset */
	charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);

	/* Send string */
	for (i = 0; i < strlen(str) && i < 0x28; i++)
		charlcd_4bit_char(lcd, str[i]);
}

static void charlcd_4bit_init(struct charlcd *lcd)
{
	/* These commands cannot be checked with the busy flag */
	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
	msleep(5);
	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
	udelay(100);
	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
	udelay(100);
	/* Go to 4bit mode */
	writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
	udelay(100);
	/*
	 * 4bit mode, 2 lines, 5x8 font, after this the number of lines
	 * and the font cannot be changed until the next initialization sequence
	 */
	charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
	charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
	charlcd_4bit_command(lcd, HD_CLEAR);
	charlcd_4bit_command(lcd, HD_HOME);
	/* Put something useful in the display */
	charlcd_4bit_print(lcd, 0, "ARM Linux");
	charlcd_4bit_print(lcd, 1, UTS_RELEASE);
}

static void charlcd_init_work(struct work_struct *work)
{
	struct charlcd *lcd =
		container_of(work, struct charlcd, init_work.work);

	charlcd_4bit_init(lcd);
}

static int __init charlcd_probe(struct platform_device *pdev)
{
	int ret;
	struct charlcd *lcd;
	struct resource *res;

	lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL);
	if (!lcd)
		return -ENOMEM;

	lcd->dev = &pdev->dev;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		ret = -ENOENT;
		goto out_no_resource;
	}
	lcd->phybase = res->start;
	lcd->physize = resource_size(res);

	if (request_mem_region(lcd->phybase, lcd->physize,
			       DRIVERNAME) == NULL) {
		ret = -EBUSY;
		goto out_no_memregion;
	}

	lcd->virtbase = ioremap(lcd->phybase, lcd->physize);
	if (!lcd->virtbase) {
		ret = -ENOMEM;
		goto out_no_memregion;
	}

	lcd->irq = platform_get_irq(pdev, 0);
	/* If no IRQ is supplied, we'll survive without it */
	if (lcd->irq >= 0) {
		if (request_irq(lcd->irq, charlcd_interrupt, IRQF_DISABLED,
				DRIVERNAME, lcd)) {
			ret = -EIO;
			goto out_no_irq;
		}
	}

	platform_set_drvdata(pdev, lcd);

	/*
	 * Initialize the display in a delayed work, because
	 * it is VERY slow and would slow down the boot of the system.
	 */
	INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
	schedule_delayed_work(&lcd->init_work, 0);

	dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n",
		lcd->phybase);

	return 0;

out_no_irq:
	iounmap(lcd->virtbase);
out_no_memregion:
	release_mem_region(lcd->phybase, SZ_4K);
out_no_resource:
	kfree(lcd);
	return ret;
}

static int __exit charlcd_remove(struct platform_device *pdev)
{
	struct charlcd *lcd = platform_get_drvdata(pdev);

	if (lcd) {
		free_irq(lcd->irq, lcd);
		iounmap(lcd->virtbase);
		release_mem_region(lcd->phybase, lcd->physize);
		kfree(lcd);
	}

	return 0;
}

static int charlcd_suspend(struct device *dev)
{
	struct platform_device *pdev = to_platform_device(dev);
	struct charlcd *lcd = platform_get_drvdata(pdev);

	/* Power the display off */
	charlcd_4bit_command(lcd, HD_DISPCTRL);
	return 0;
}

static int charlcd_resume(struct device *dev)
{
	struct platform_device *pdev = to_platform_device(dev);
	struct charlcd *lcd = platform_get_drvdata(pdev);

	/* Turn the display back on */
	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
	return 0;
}

static const struct dev_pm_ops charlcd_pm_ops = {
	.suspend = charlcd_suspend,
	.resume = charlcd_resume,
};

static struct platform_driver charlcd_driver = {
	.driver = {
		.name = DRIVERNAME,
		.owner = THIS_MODULE,
		.pm = &charlcd_pm_ops,
	},
	.remove = __exit_p(charlcd_remove),
};

module_platform_driver_probe(charlcd_driver, charlcd_probe);

MODULE_AUTHOR("Linus Walleij <triad@df.lth.se>");
MODULE_DESCRIPTION("ARM Character LCD Driver");
MODULE_LICENSE("GPL v2");