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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Driver for the on-board character LCD found on some ARM reference boards
4 * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it
5 * https://en.wikipedia.org/wiki/HD44780_Character_LCD
6 * Currently it will just display the text "ARM Linux" and the linux version
7 *
8 * Author: Linus Walleij <[email protected]>
9 */
10#include <linux/completion.h>
11#include <linux/container_of.h>
12#include <linux/delay.h>
13#include <linux/err.h>
14#include <linux/init.h>
15#include <linux/interrupt.h>
16#include <linux/iopoll.h>
17#include <linux/platform_device.h>
18#include <linux/string.h>
19#include <linux/types.h>
20#include <linux/workqueue.h>
21#include <generated/utsrelease.h>
22
23#define DRIVERNAME "arm-charlcd"
24#define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
25
26/* Offsets to registers */
27#define CHAR_COM 0x00U
28#define CHAR_DAT 0x04U
29#define CHAR_RD 0x08U
30#define CHAR_RAW 0x0CU
31#define CHAR_MASK 0x10U
32#define CHAR_STAT 0x14U
33
34#define CHAR_RAW_CLEAR 0x00000000U
35#define CHAR_RAW_VALID 0x00000100U
36
37/* Hitachi HD44780 display commands */
38#define HD_CLEAR 0x01U
39#define HD_HOME 0x02U
40#define HD_ENTRYMODE 0x04U
41#define HD_ENTRYMODE_INCREMENT 0x02U
42#define HD_ENTRYMODE_SHIFT 0x01U
43#define HD_DISPCTRL 0x08U
44#define HD_DISPCTRL_ON 0x04U
45#define HD_DISPCTRL_CURSOR_ON 0x02U
46#define HD_DISPCTRL_CURSOR_BLINK 0x01U
47#define HD_CRSR_SHIFT 0x10U
48#define HD_CRSR_SHIFT_DISPLAY 0x08U
49#define HD_CRSR_SHIFT_DISPLAY_RIGHT 0x04U
50#define HD_FUNCSET 0x20U
51#define HD_FUNCSET_8BIT 0x10U
52#define HD_FUNCSET_2_LINES 0x08U
53#define HD_FUNCSET_FONT_5X10 0x04U
54#define HD_SET_CGRAM 0x40U
55#define HD_SET_DDRAM 0x80U
56#define HD_BUSY_FLAG 0x80U
57
58/**
59 * struct charlcd - Private data structure
60 * @dev: a pointer back to containing device
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 * @init_work: delayed work structure to initialize the display on boot
65 */
66struct charlcd {
67 struct device *dev;
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() returned %d waiting for ready\n",
102 ret);
103 return;
104 }
105
106 if (ret == 0) {
107 dev_err(lcd->dev, "charlcd controller timed out waiting for ready\n");
108 return;
109 }
110}
111
112static u8 charlcd_4bit_read_char(struct charlcd *lcd)
113{
114 u8 data;
115 u32 val;
116
117 /* If we can, use an IRQ to wait for the data, else poll */
118 if (lcd->irq >= 0)
119 charlcd_wait_complete_irq(lcd);
120 else {
121 udelay(100);
122 readl_poll_timeout_atomic(lcd->virtbase + CHAR_RAW, val,
123 val & CHAR_RAW_VALID, 100, 1000);
124 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
125 }
126 msleep(1);
127
128 /* Read the 4 high bits of the data */
129 data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
130
131 /*
132 * The second read for the low bits does not trigger an IRQ
133 * so in this case we have to poll for the 4 lower bits
134 */
135 udelay(100);
136 readl_poll_timeout_atomic(lcd->virtbase + CHAR_RAW, val,
137 val & CHAR_RAW_VALID, 100, 1000);
138 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
139 msleep(1);
140
141 /* Read the 4 low bits of the data */
142 data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
143
144 return data;
145}
146
147static bool charlcd_4bit_read_bf(struct charlcd *lcd)
148{
149 if (lcd->irq >= 0) {
150 /*
151 * If we'll use IRQs to wait for the busyflag, clear any
152 * pending flag and enable IRQ
153 */
154 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
155 init_completion(&lcd->complete);
156 writel(0x01, lcd->virtbase + CHAR_MASK);
157 }
158 readl(lcd->virtbase + CHAR_COM);
159
160 return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG;
161}
162
163static void charlcd_4bit_wait_busy(struct charlcd *lcd)
164{
165 int retries = 50;
166
167 udelay(100);
168 while (charlcd_4bit_read_bf(lcd) && retries)
169 retries--;
170 if (!retries)
171 dev_err(lcd->dev, "timeout waiting for busyflag\n");
172}
173
174static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
175{
176 u32 cmdlo = (cmd << 4) & 0xf0;
177 u32 cmdhi = (cmd & 0xf0);
178
179 writel(cmdhi, lcd->virtbase + CHAR_COM);
180 udelay(10);
181 writel(cmdlo, lcd->virtbase + CHAR_COM);
182 charlcd_4bit_wait_busy(lcd);
183}
184
185static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
186{
187 u32 chlo = (ch << 4) & 0xf0;
188 u32 chhi = (ch & 0xf0);
189
190 writel(chhi, lcd->virtbase + CHAR_DAT);
191 udelay(10);
192 writel(chlo, lcd->virtbase + CHAR_DAT);
193 charlcd_4bit_wait_busy(lcd);
194}
195
196static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
197{
198 u8 offset;
199 int i;
200
201 /*
202 * We support line 0, 1
203 * Line 1 runs from 0x00..0x27
204 * Line 2 runs from 0x28..0x4f
205 */
206 if (line == 0)
207 offset = 0;
208 else if (line == 1)
209 offset = 0x28;
210 else
211 return;
212
213 /* Set offset */
214 charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
215
216 /* Send string */
217 for (i = 0; i < strlen(str) && i < 0x28; i++)
218 charlcd_4bit_char(lcd, str[i]);
219}
220
221static void charlcd_4bit_init(struct charlcd *lcd)
222{
223 /* These commands cannot be checked with the busy flag */
224 writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
225 msleep(5);
226 writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
227 udelay(100);
228 writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
229 udelay(100);
230 /* Go to 4bit mode */
231 writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
232 udelay(100);
233 /*
234 * 4bit mode, 2 lines, 5x8 font, after this the number of lines
235 * and the font cannot be changed until the next initialization sequence
236 */
237 charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
238 charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
239 charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
240 charlcd_4bit_command(lcd, HD_CLEAR);
241 charlcd_4bit_command(lcd, HD_HOME);
242 /* Put something useful in the display */
243 charlcd_4bit_print(lcd, 0, "ARM Linux");
244 charlcd_4bit_print(lcd, 1, UTS_RELEASE);
245}
246
247static void charlcd_init_work(struct work_struct *work)
248{
249 struct charlcd *lcd =
250 container_of(work, struct charlcd, init_work.work);
251
252 charlcd_4bit_init(lcd);
253}
254
255static int __init charlcd_probe(struct platform_device *pdev)
256{
257 struct device *dev = &pdev->dev;
258 int ret;
259 struct charlcd *lcd;
260
261 lcd = devm_kzalloc(dev, sizeof(*lcd), GFP_KERNEL);
262 if (!lcd)
263 return -ENOMEM;
264
265 lcd->dev = &pdev->dev;
266
267 lcd->virtbase = devm_platform_ioremap_resource(pdev, 0);
268 if (IS_ERR(lcd->virtbase))
269 return PTR_ERR(lcd->virtbase);
270
271 lcd->irq = platform_get_irq(pdev, 0);
272 /* If no IRQ is supplied, we'll survive without it */
273 if (lcd->irq >= 0) {
274 ret = devm_request_irq(dev, lcd->irq, charlcd_interrupt, 0, DRIVERNAME, lcd);
275 if (ret)
276 return ret;
277 }
278
279 platform_set_drvdata(pdev, lcd);
280
281 /*
282 * Initialize the display in a delayed work, because
283 * it is VERY slow and would slow down the boot of the system.
284 */
285 INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
286 schedule_delayed_work(&lcd->init_work, 0);
287
288 return 0;
289}
290
291static int charlcd_suspend(struct device *dev)
292{
293 struct charlcd *lcd = dev_get_drvdata(dev);
294
295 /* Power the display off */
296 charlcd_4bit_command(lcd, HD_DISPCTRL);
297 return 0;
298}
299
300static int charlcd_resume(struct device *dev)
301{
302 struct charlcd *lcd = dev_get_drvdata(dev);
303
304 /* Turn the display back on */
305 charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
306 return 0;
307}
308
309static const struct dev_pm_ops charlcd_pm_ops = {
310 .suspend = charlcd_suspend,
311 .resume = charlcd_resume,
312};
313
314static const struct of_device_id charlcd_match[] = {
315 { .compatible = "arm,versatile-lcd", },
316 {}
317};
318
319static struct platform_driver charlcd_driver = {
320 .driver = {
321 .name = DRIVERNAME,
322 .pm = &charlcd_pm_ops,
323 .suppress_bind_attrs = true,
324 .of_match_table = charlcd_match,
325 },
326};
327builtin_platform_driver_probe(charlcd_driver, charlcd_probe);