1/*
2 * Driver for the on-board character LCD found on some ARM reference boards
3 * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it
4 * http://en.wikipedia.org/wiki/HD44780_Character_LCD
5 * Currently it will just display the text "ARM Linux" and the linux version
6 *
7 * License terms: GNU General Public License (GPL) version 2
8 * Author: Linus Walleij <triad@df.lth.se>
9 */
10#include <linux/init.h>
11#include <linux/module.h>
12#include <linux/interrupt.h>
13#include <linux/platform_device.h>
14#include <linux/of.h>
15#include <linux/completion.h>
16#include <linux/delay.h>
17#include <linux/io.h>
18#include <linux/slab.h>
19#include <linux/workqueue.h>
20#include <generated/utsrelease.h>
21
22#define DRIVERNAME "arm-charlcd"
23#define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
24
25/* Offsets to registers */
26#define CHAR_COM	0x00U
27#define CHAR_DAT	0x04U
28#define CHAR_RD		0x08U
29#define CHAR_RAW	0x0CU
30#define CHAR_MASK	0x10U
31#define CHAR_STAT	0x14U
32
33#define CHAR_RAW_CLEAR	0x00000000U
34#define CHAR_RAW_VALID	0x00000100U
35
36/* Hitachi HD44780 display commands */
37#define HD_CLEAR			0x01U
38#define HD_HOME				0x02U
39#define HD_ENTRYMODE			0x04U
40#define HD_ENTRYMODE_INCREMENT		0x02U
41#define HD_ENTRYMODE_SHIFT		0x01U
42#define HD_DISPCTRL			0x08U
43#define HD_DISPCTRL_ON			0x04U
44#define HD_DISPCTRL_CURSOR_ON		0x02U
45#define HD_DISPCTRL_CURSOR_BLINK	0x01U
46#define HD_CRSR_SHIFT			0x10U
47#define HD_CRSR_SHIFT_DISPLAY		0x08U
48#define HD_CRSR_SHIFT_DISPLAY_RIGHT	0x04U
49#define HD_FUNCSET			0x20U
50#define HD_FUNCSET_8BIT			0x10U
51#define HD_FUNCSET_2_LINES		0x08U
52#define HD_FUNCSET_FONT_5X10		0x04U
53#define HD_SET_CGRAM			0x40U
54#define HD_SET_DDRAM			0x80U
55#define HD_BUSY_FLAG			0x80U
56
57/**
58 * @dev: a pointer back to containing device
59 * @phybase: the offset to the controller in physical memory
60 * @physize: the size of the physical page
61 * @virtbase: the offset to the controller in virtual memory
62 * @irq: reserved interrupt number
63 * @complete: completion structure for the last LCD command
64 */
65struct charlcd {
66	struct device *dev;
67	u32 phybase;
68	u32 physize;
69	void __iomem *virtbase;
70	int irq;
71	struct completion complete;
72	struct delayed_work init_work;
73};
74
75static irqreturn_t charlcd_interrupt(int irq, void *data)
76{
77	struct charlcd *lcd = data;
78	u8 status;
79
80	status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
81	/* Clear IRQ */
82	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
83	if (status)
84		complete(&lcd->complete);
85	else
86		dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status);
87	return IRQ_HANDLED;
88}
89
90
91static void charlcd_wait_complete_irq(struct charlcd *lcd)
92{
93	int ret;
94
95	ret = wait_for_completion_interruptible_timeout(&lcd->complete,
96							CHARLCD_TIMEOUT);
97	/* Disable IRQ after completion */
98	writel(0x00, lcd->virtbase + CHAR_MASK);
99
100	if (ret < 0) {
101		dev_err(lcd->dev,
102			"wait_for_completion_interruptible_timeout() "
103			"returned %d waiting for ready\n", ret);
104		return;
105	}
106
107	if (ret == 0) {
108		dev_err(lcd->dev, "charlcd controller timed out "
109			"waiting for ready\n");
110		return;
111	}
112}
113
114static u8 charlcd_4bit_read_char(struct charlcd *lcd)
115{
116	u8 data;
117	u32 val;
118	int i;
119
120	/* If we can, use an IRQ to wait for the data, else poll */
121	if (lcd->irq >= 0)
122		charlcd_wait_complete_irq(lcd);
123	else {
124		i = 0;
125		val = 0;
126		while (!(val & CHAR_RAW_VALID) && i < 10) {
127			udelay(100);
128			val = readl(lcd->virtbase + CHAR_RAW);
129			i++;
130		}
131
132		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
133	}
134	msleep(1);
135
136	/* Read the 4 high bits of the data */
137	data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
138
139	/*
140	 * The second read for the low bits does not trigger an IRQ
141	 * so in this case we have to poll for the 4 lower bits
142	 */
143	i = 0;
144	val = 0;
145	while (!(val & CHAR_RAW_VALID) && i < 10) {
146		udelay(100);
147		val = readl(lcd->virtbase + CHAR_RAW);
148		i++;
149	}
150	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
151	msleep(1);
152
153	/* Read the 4 low bits of the data */
154	data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
155
156	return data;
157}
158
159static bool charlcd_4bit_read_bf(struct charlcd *lcd)
160{
161	if (lcd->irq >= 0) {
162		/*
163		 * If we'll use IRQs to wait for the busyflag, clear any
164		 * pending flag and enable IRQ
165		 */
166		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
167		init_completion(&lcd->complete);
168		writel(0x01, lcd->virtbase + CHAR_MASK);
169	}
170	readl(lcd->virtbase + CHAR_COM);
171	return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false;
172}
173
174static void charlcd_4bit_wait_busy(struct charlcd *lcd)
175{
176	int retries = 50;
177
178	udelay(100);
179	while (charlcd_4bit_read_bf(lcd) && retries)
180		retries--;
181	if (!retries)
182		dev_err(lcd->dev, "timeout waiting for busyflag\n");
183}
184
185static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
186{
187	u32 cmdlo = (cmd << 4) & 0xf0;
188	u32 cmdhi = (cmd & 0xf0);
189
190	writel(cmdhi, lcd->virtbase + CHAR_COM);
191	udelay(10);
192	writel(cmdlo, lcd->virtbase + CHAR_COM);
193	charlcd_4bit_wait_busy(lcd);
194}
195
196static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
197{
198	u32 chlo = (ch << 4) & 0xf0;
199	u32 chhi = (ch & 0xf0);
200
201	writel(chhi, lcd->virtbase + CHAR_DAT);
202	udelay(10);
203	writel(chlo, lcd->virtbase + CHAR_DAT);
204	charlcd_4bit_wait_busy(lcd);
205}
206
207static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
208{
209	u8 offset;
210	int i;
211
212	/*
213	 * We support line 0, 1
214	 * Line 1 runs from 0x00..0x27
215	 * Line 2 runs from 0x28..0x4f
216	 */
217	if (line == 0)
218		offset = 0;
219	else if (line == 1)
220		offset = 0x28;
221	else
222		return;
223
224	/* Set offset */
225	charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
226
227	/* Send string */
228	for (i = 0; i < strlen(str) && i < 0x28; i++)
229		charlcd_4bit_char(lcd, str[i]);
230}
231
232static void charlcd_4bit_init(struct charlcd *lcd)
233{
234	/* These commands cannot be checked with the busy flag */
235	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
236	msleep(5);
237	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
238	udelay(100);
239	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
240	udelay(100);
241	/* Go to 4bit mode */
242	writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
243	udelay(100);
244	/*
245	 * 4bit mode, 2 lines, 5x8 font, after this the number of lines
246	 * and the font cannot be changed until the next initialization sequence
247	 */
248	charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
249	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
250	charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
251	charlcd_4bit_command(lcd, HD_CLEAR);
252	charlcd_4bit_command(lcd, HD_HOME);
253	/* Put something useful in the display */
254	charlcd_4bit_print(lcd, 0, "ARM Linux");
255	charlcd_4bit_print(lcd, 1, UTS_RELEASE);
256}
257
258static void charlcd_init_work(struct work_struct *work)
259{
260	struct charlcd *lcd =
261		container_of(work, struct charlcd, init_work.work);
262
263	charlcd_4bit_init(lcd);
264}
265
266static int __init charlcd_probe(struct platform_device *pdev)
267{
268	int ret;
269	struct charlcd *lcd;
270	struct resource *res;
271
272	lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL);
273	if (!lcd)
274		return -ENOMEM;
275
276	lcd->dev = &pdev->dev;
277
278	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
279	if (!res) {
280		ret = -ENOENT;
281		goto out_no_resource;
282	}
283	lcd->phybase = res->start;
284	lcd->physize = resource_size(res);
285
286	if (request_mem_region(lcd->phybase, lcd->physize,
287			       DRIVERNAME) == NULL) {
288		ret = -EBUSY;
289		goto out_no_memregion;
290	}
291
292	lcd->virtbase = ioremap(lcd->phybase, lcd->physize);
293	if (!lcd->virtbase) {
294		ret = -ENOMEM;
295		goto out_no_memregion;
296	}
297
298	lcd->irq = platform_get_irq(pdev, 0);
299	/* If no IRQ is supplied, we'll survive without it */
300	if (lcd->irq >= 0) {
301		if (request_irq(lcd->irq, charlcd_interrupt, 0,
302				DRIVERNAME, lcd)) {
303			ret = -EIO;
304			goto out_no_irq;
305		}
306	}
307
308	platform_set_drvdata(pdev, lcd);
309
310	/*
311	 * Initialize the display in a delayed work, because
312	 * it is VERY slow and would slow down the boot of the system.
313	 */
314	INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
315	schedule_delayed_work(&lcd->init_work, 0);
316
317	dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n",
318		lcd->phybase);
319
320	return 0;
321
322out_no_irq:
323	iounmap(lcd->virtbase);
324out_no_memregion:
325	release_mem_region(lcd->phybase, SZ_4K);
326out_no_resource:
327	kfree(lcd);
328	return ret;
329}
330
331static int __exit charlcd_remove(struct platform_device *pdev)
332{
333	struct charlcd *lcd = platform_get_drvdata(pdev);
334
335	if (lcd) {
336		free_irq(lcd->irq, lcd);
337		iounmap(lcd->virtbase);
338		release_mem_region(lcd->phybase, lcd->physize);
339		kfree(lcd);
340	}
341
342	return 0;
343}
344
345static int charlcd_suspend(struct device *dev)
346{
347	struct platform_device *pdev = to_platform_device(dev);
348	struct charlcd *lcd = platform_get_drvdata(pdev);
349
350	/* Power the display off */
351	charlcd_4bit_command(lcd, HD_DISPCTRL);
352	return 0;
353}
354
355static int charlcd_resume(struct device *dev)
356{
357	struct platform_device *pdev = to_platform_device(dev);
358	struct charlcd *lcd = platform_get_drvdata(pdev);
359
360	/* Turn the display back on */
361	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
362	return 0;
363}
364
365static const struct dev_pm_ops charlcd_pm_ops = {
366	.suspend = charlcd_suspend,
367	.resume = charlcd_resume,
368};
369
370static const struct of_device_id charlcd_match[] = {
371	{ .compatible = "arm,versatile-lcd", },
372	{}
373};
374
375static struct platform_driver charlcd_driver = {
376	.driver = {
377		.name = DRIVERNAME,
378		.pm = &charlcd_pm_ops,
379		.of_match_table = of_match_ptr(charlcd_match),
380	},
381	.remove = __exit_p(charlcd_remove),
382};
383
384module_platform_driver_probe(charlcd_driver, charlcd_probe);
385
386MODULE_AUTHOR("Linus Walleij <triad@df.lth.se>");
387MODULE_DESCRIPTION("ARM Character LCD Driver");
388MODULE_LICENSE("GPL v2");
389