Root/drivers/misc/arm-charlcd.c

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/completion.h>
15#include <linux/delay.h>
16#include <linux/io.h>
17#include <linux/slab.h>
18#include <linux/workqueue.h>
19#include <generated/utsrelease.h>
20
21#define DRIVERNAME "arm-charlcd"
22#define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
23
24/* Offsets to registers */
25#define CHAR_COM 0x00U
26#define CHAR_DAT 0x04U
27#define CHAR_RD 0x08U
28#define CHAR_RAW 0x0CU
29#define CHAR_MASK 0x10U
30#define CHAR_STAT 0x14U
31
32#define CHAR_RAW_CLEAR 0x00000000U
33#define CHAR_RAW_VALID 0x00000100U
34
35/* Hitachi HD44780 display commands */
36#define HD_CLEAR 0x01U
37#define HD_HOME 0x02U
38#define HD_ENTRYMODE 0x04U
39#define HD_ENTRYMODE_INCREMENT 0x02U
40#define HD_ENTRYMODE_SHIFT 0x01U
41#define HD_DISPCTRL 0x08U
42#define HD_DISPCTRL_ON 0x04U
43#define HD_DISPCTRL_CURSOR_ON 0x02U
44#define HD_DISPCTRL_CURSOR_BLINK 0x01U
45#define HD_CRSR_SHIFT 0x10U
46#define HD_CRSR_SHIFT_DISPLAY 0x08U
47#define HD_CRSR_SHIFT_DISPLAY_RIGHT 0x04U
48#define HD_FUNCSET 0x20U
49#define HD_FUNCSET_8BIT 0x10U
50#define HD_FUNCSET_2_LINES 0x08U
51#define HD_FUNCSET_FONT_5X10 0x04U
52#define HD_SET_CGRAM 0x40U
53#define HD_SET_DDRAM 0x80U
54#define HD_BUSY_FLAG 0x80U
55
56/**
57 * @dev: a pointer back to containing device
58 * @phybase: the offset to the controller in physical memory
59 * @physize: the size of the physical page
60 * @virtbase: the offset to the controller in virtual memory
61 * @irq: reserved interrupt number
62 * @complete: completion structure for the last LCD command
63 */
64struct charlcd {
65    struct device *dev;
66    u32 phybase;
67    u32 physize;
68    void __iomem *virtbase;
69    int irq;
70    struct completion complete;
71    struct delayed_work init_work;
72};
73
74static irqreturn_t charlcd_interrupt(int irq, void *data)
75{
76    struct charlcd *lcd = data;
77    u8 status;
78
79    status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
80    /* Clear IRQ */
81    writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
82    if (status)
83        complete(&lcd->complete);
84    else
85        dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status);
86    return IRQ_HANDLED;
87}
88
89
90static void charlcd_wait_complete_irq(struct charlcd *lcd)
91{
92    int ret;
93
94    ret = wait_for_completion_interruptible_timeout(&lcd->complete,
95                            CHARLCD_TIMEOUT);
96    /* Disable IRQ after completion */
97    writel(0x00, lcd->virtbase + CHAR_MASK);
98
99    if (ret < 0) {
100        dev_err(lcd->dev,
101            "wait_for_completion_interruptible_timeout() "
102            "returned %d waiting for ready\n", ret);
103        return;
104    }
105
106    if (ret == 0) {
107        dev_err(lcd->dev, "charlcd controller timed out "
108            "waiting for ready\n");
109        return;
110    }
111}
112
113static u8 charlcd_4bit_read_char(struct charlcd *lcd)
114{
115    u8 data;
116    u32 val;
117    int i;
118
119    /* If we can, use an IRQ to wait for the data, else poll */
120    if (lcd->irq >= 0)
121        charlcd_wait_complete_irq(lcd);
122    else {
123        i = 0;
124        val = 0;
125        while (!(val & CHAR_RAW_VALID) && i < 10) {
126            udelay(100);
127            val = readl(lcd->virtbase + CHAR_RAW);
128            i++;
129        }
130
131        writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
132    }
133    msleep(1);
134
135    /* Read the 4 high bits of the data */
136    data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
137
138    /*
139     * The second read for the low bits does not trigger an IRQ
140     * so in this case we have to poll for the 4 lower bits
141     */
142    i = 0;
143    val = 0;
144    while (!(val & CHAR_RAW_VALID) && i < 10) {
145        udelay(100);
146        val = readl(lcd->virtbase + CHAR_RAW);
147        i++;
148    }
149    writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
150    msleep(1);
151
152    /* Read the 4 low bits of the data */
153    data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
154
155    return data;
156}
157
158static bool charlcd_4bit_read_bf(struct charlcd *lcd)
159{
160    if (lcd->irq >= 0) {
161        /*
162         * If we'll use IRQs to wait for the busyflag, clear any
163         * pending flag and enable IRQ
164         */
165        writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
166        init_completion(&lcd->complete);
167        writel(0x01, lcd->virtbase + CHAR_MASK);
168    }
169    readl(lcd->virtbase + CHAR_COM);
170    return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false;
171}
172
173static void charlcd_4bit_wait_busy(struct charlcd *lcd)
174{
175    int retries = 50;
176
177    udelay(100);
178    while (charlcd_4bit_read_bf(lcd) && retries)
179        retries--;
180    if (!retries)
181        dev_err(lcd->dev, "timeout waiting for busyflag\n");
182}
183
184static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
185{
186    u32 cmdlo = (cmd << 4) & 0xf0;
187    u32 cmdhi = (cmd & 0xf0);
188
189    writel(cmdhi, lcd->virtbase + CHAR_COM);
190    udelay(10);
191    writel(cmdlo, lcd->virtbase + CHAR_COM);
192    charlcd_4bit_wait_busy(lcd);
193}
194
195static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
196{
197    u32 chlo = (ch << 4) & 0xf0;
198    u32 chhi = (ch & 0xf0);
199
200    writel(chhi, lcd->virtbase + CHAR_DAT);
201    udelay(10);
202    writel(chlo, lcd->virtbase + CHAR_DAT);
203    charlcd_4bit_wait_busy(lcd);
204}
205
206static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
207{
208    u8 offset;
209    int i;
210
211    /*
212     * We support line 0, 1
213     * Line 1 runs from 0x00..0x27
214     * Line 2 runs from 0x28..0x4f
215     */
216    if (line == 0)
217        offset = 0;
218    else if (line == 1)
219        offset = 0x28;
220    else
221        return;
222
223    /* Set offset */
224    charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
225
226    /* Send string */
227    for (i = 0; i < strlen(str) && i < 0x28; i++)
228        charlcd_4bit_char(lcd, str[i]);
229}
230
231static void charlcd_4bit_init(struct charlcd *lcd)
232{
233    /* These commands cannot be checked with the busy flag */
234    writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
235    msleep(5);
236    writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
237    udelay(100);
238    writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
239    udelay(100);
240    /* Go to 4bit mode */
241    writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
242    udelay(100);
243    /*
244     * 4bit mode, 2 lines, 5x8 font, after this the number of lines
245     * and the font cannot be changed until the next initialization sequence
246     */
247    charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
248    charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
249    charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
250    charlcd_4bit_command(lcd, HD_CLEAR);
251    charlcd_4bit_command(lcd, HD_HOME);
252    /* Put something useful in the display */
253    charlcd_4bit_print(lcd, 0, "ARM Linux");
254    charlcd_4bit_print(lcd, 1, UTS_RELEASE);
255}
256
257static void charlcd_init_work(struct work_struct *work)
258{
259    struct charlcd *lcd =
260        container_of(work, struct charlcd, init_work.work);
261
262    charlcd_4bit_init(lcd);
263}
264
265static int __init charlcd_probe(struct platform_device *pdev)
266{
267    int ret;
268    struct charlcd *lcd;
269    struct resource *res;
270
271    lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL);
272    if (!lcd)
273        return -ENOMEM;
274
275    lcd->dev = &pdev->dev;
276
277    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
278    if (!res) {
279        ret = -ENOENT;
280        goto out_no_resource;
281    }
282    lcd->phybase = res->start;
283    lcd->physize = resource_size(res);
284
285    if (request_mem_region(lcd->phybase, lcd->physize,
286                   DRIVERNAME) == NULL) {
287        ret = -EBUSY;
288        goto out_no_memregion;
289    }
290
291    lcd->virtbase = ioremap(lcd->phybase, lcd->physize);
292    if (!lcd->virtbase) {
293        ret = -ENOMEM;
294        goto out_no_remap;
295    }
296
297    lcd->irq = platform_get_irq(pdev, 0);
298    /* If no IRQ is supplied, we'll survive without it */
299    if (lcd->irq >= 0) {
300        if (request_irq(lcd->irq, charlcd_interrupt, IRQF_DISABLED,
301                DRIVERNAME, lcd)) {
302            ret = -EIO;
303            goto out_no_irq;
304        }
305    }
306
307    platform_set_drvdata(pdev, lcd);
308
309    /*
310     * Initialize the display in a delayed work, because
311     * it is VERY slow and would slow down the boot of the system.
312     */
313    INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
314    schedule_delayed_work(&lcd->init_work, 0);
315
316    dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n",
317        lcd->phybase);
318
319    return 0;
320
321out_no_irq:
322    iounmap(lcd->virtbase);
323out_no_remap:
324    platform_set_drvdata(pdev, NULL);
325out_no_memregion:
326    release_mem_region(lcd->phybase, SZ_4K);
327out_no_resource:
328    kfree(lcd);
329    return ret;
330}
331
332static int __exit charlcd_remove(struct platform_device *pdev)
333{
334    struct charlcd *lcd = platform_get_drvdata(pdev);
335
336    if (lcd) {
337        free_irq(lcd->irq, lcd);
338        iounmap(lcd->virtbase);
339        release_mem_region(lcd->phybase, lcd->physize);
340        platform_set_drvdata(pdev, NULL);
341        kfree(lcd);
342    }
343
344    return 0;
345}
346
347static int charlcd_suspend(struct device *dev)
348{
349    struct platform_device *pdev = to_platform_device(dev);
350    struct charlcd *lcd = platform_get_drvdata(pdev);
351
352    /* Power the display off */
353    charlcd_4bit_command(lcd, HD_DISPCTRL);
354    return 0;
355}
356
357static int charlcd_resume(struct device *dev)
358{
359    struct platform_device *pdev = to_platform_device(dev);
360    struct charlcd *lcd = platform_get_drvdata(pdev);
361
362    /* Turn the display back on */
363    charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
364    return 0;
365}
366
367static const struct dev_pm_ops charlcd_pm_ops = {
368    .suspend = charlcd_suspend,
369    .resume = charlcd_resume,
370};
371
372static struct platform_driver charlcd_driver = {
373    .driver = {
374        .name = DRIVERNAME,
375        .owner = THIS_MODULE,
376        .pm = &charlcd_pm_ops,
377    },
378    .remove = __exit_p(charlcd_remove),
379};
380
381static int __init charlcd_init(void)
382{
383    return platform_driver_probe(&charlcd_driver, charlcd_probe);
384}
385
386static void __exit charlcd_exit(void)
387{
388    platform_driver_unregister(&charlcd_driver);
389}
390
391module_init(charlcd_init);
392module_exit(charlcd_exit);
393
394MODULE_AUTHOR("Linus Walleij <triad@df.lth.se>");
395MODULE_DESCRIPTION("ARM Character LCD Driver");
396MODULE_LICENSE("GPL v2");
397

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