1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2016 Imagination Technologies
4 * Author: Paul Burton <paul.burton@mips.com>
5 */
6
7#include <generated/utsrelease.h>
8#include <linux/kernel.h>
9#include <linux/io.h>
10#include <linux/mfd/syscon.h>
11#include <linux/module.h>
12#include <linux/of_address.h>
13#include <linux/of_platform.h>
14#include <linux/platform_device.h>
15#include <linux/regmap.h>
16#include <linux/slab.h>
17#include <linux/sysfs.h>
18
19struct img_ascii_lcd_ctx;
20
21/**
22 * struct img_ascii_lcd_config - Configuration information about an LCD model
23 * @num_chars: the number of characters the LCD can display
24 * @external_regmap: true if registers are in a system controller, else false
25 * @update: function called to update the LCD
26 */
27struct img_ascii_lcd_config {
28	unsigned int num_chars;
29	bool external_regmap;
30	void (*update)(struct img_ascii_lcd_ctx *ctx);
31};
32
33/**
34 * struct img_ascii_lcd_ctx - Private data structure
35 * @pdev: the ASCII LCD platform device
36 * @base: the base address of the LCD registers
37 * @regmap: the regmap through which LCD registers are accessed
38 * @offset: the offset within regmap to the start of the LCD registers
39 * @cfg: pointer to the LCD model configuration
40 * @message: the full message to display or scroll on the LCD
41 * @message_len: the length of the @message string
42 * @scroll_pos: index of the first character of @message currently displayed
43 * @scroll_rate: scroll interval in jiffies
44 * @timer: timer used to implement scrolling
45 * @curr: the string currently displayed on the LCD
46 */
47struct img_ascii_lcd_ctx {
48	struct platform_device *pdev;
49	union {
50		void __iomem *base;
51		struct regmap *regmap;
52	};
53	u32 offset;
54	const struct img_ascii_lcd_config *cfg;
55	char *message;
56	unsigned int message_len;
57	unsigned int scroll_pos;
58	unsigned int scroll_rate;
59	struct timer_list timer;
60	char curr[] __aligned(8);
61};
62
63/*
64 * MIPS Boston development board
65 */
66
67static void boston_update(struct img_ascii_lcd_ctx *ctx)
68{
69	ulong val;
70
71#if BITS_PER_LONG == 64
72	val = *((u64 *)&ctx->curr[0]);
73	__raw_writeq(val, ctx->base);
74#elif BITS_PER_LONG == 32
75	val = *((u32 *)&ctx->curr[0]);
76	__raw_writel(val, ctx->base);
77	val = *((u32 *)&ctx->curr[4]);
78	__raw_writel(val, ctx->base + 4);
79#else
80# error Not 32 or 64 bit
81#endif
82}
83
84static struct img_ascii_lcd_config boston_config = {
85	.num_chars = 8,
86	.update = boston_update,
87};
88
89/*
90 * MIPS Malta development board
91 */
92
93static void malta_update(struct img_ascii_lcd_ctx *ctx)
94{
95	unsigned int i;
96	int err = 0;
97
98	for (i = 0; i < ctx->cfg->num_chars; i++) {
99		err = regmap_write(ctx->regmap,
100				   ctx->offset + (i * 8), ctx->curr[i]);
101		if (err)
102			break;
103	}
104
105	if (unlikely(err))
106		pr_err_ratelimited("Failed to update LCD display: %d\n", err);
107}
108
109static struct img_ascii_lcd_config malta_config = {
110	.num_chars = 8,
111	.external_regmap = true,
112	.update = malta_update,
113};
114
115/*
116 * MIPS SEAD3 development board
117 */
118
119enum {
120	SEAD3_REG_LCD_CTRL		= 0x00,
121#define SEAD3_REG_LCD_CTRL_SETDRAM	BIT(7)
122	SEAD3_REG_LCD_DATA		= 0x08,
123	SEAD3_REG_CPLD_STATUS		= 0x10,
124#define SEAD3_REG_CPLD_STATUS_BUSY	BIT(0)
125	SEAD3_REG_CPLD_DATA		= 0x18,
126#define SEAD3_REG_CPLD_DATA_BUSY	BIT(7)
127};
128
129static int sead3_wait_sm_idle(struct img_ascii_lcd_ctx *ctx)
130{
131	unsigned int status;
132	int err;
133
134	do {
135		err = regmap_read(ctx->regmap,
136				  ctx->offset + SEAD3_REG_CPLD_STATUS,
137				  &status);
138		if (err)
139			return err;
140	} while (status & SEAD3_REG_CPLD_STATUS_BUSY);
141
142	return 0;
143
144}
145
146static int sead3_wait_lcd_idle(struct img_ascii_lcd_ctx *ctx)
147{
148	unsigned int cpld_data;
149	int err;
150
151	err = sead3_wait_sm_idle(ctx);
152	if (err)
153		return err;
154
155	do {
156		err = regmap_read(ctx->regmap,
157				  ctx->offset + SEAD3_REG_LCD_CTRL,
158				  &cpld_data);
159		if (err)
160			return err;
161
162		err = sead3_wait_sm_idle(ctx);
163		if (err)
164			return err;
165
166		err = regmap_read(ctx->regmap,
167				  ctx->offset + SEAD3_REG_CPLD_DATA,
168				  &cpld_data);
169		if (err)
170			return err;
171	} while (cpld_data & SEAD3_REG_CPLD_DATA_BUSY);
172
173	return 0;
174}
175
176static void sead3_update(struct img_ascii_lcd_ctx *ctx)
177{
178	unsigned int i;
179	int err = 0;
180
181	for (i = 0; i < ctx->cfg->num_chars; i++) {
182		err = sead3_wait_lcd_idle(ctx);
183		if (err)
184			break;
185
186		err = regmap_write(ctx->regmap,
187				   ctx->offset + SEAD3_REG_LCD_CTRL,
188				   SEAD3_REG_LCD_CTRL_SETDRAM | i);
189		if (err)
190			break;
191
192		err = sead3_wait_lcd_idle(ctx);
193		if (err)
194			break;
195
196		err = regmap_write(ctx->regmap,
197				   ctx->offset + SEAD3_REG_LCD_DATA,
198				   ctx->curr[i]);
199		if (err)
200			break;
201	}
202
203	if (unlikely(err))
204		pr_err_ratelimited("Failed to update LCD display: %d\n", err);
205}
206
207static struct img_ascii_lcd_config sead3_config = {
208	.num_chars = 16,
209	.external_regmap = true,
210	.update = sead3_update,
211};
212
213static const struct of_device_id img_ascii_lcd_matches[] = {
214	{ .compatible = "img,boston-lcd", .data = &boston_config },
215	{ .compatible = "mti,malta-lcd", .data = &malta_config },
216	{ .compatible = "mti,sead3-lcd", .data = &sead3_config },
217	{ /* sentinel */ }
218};
219MODULE_DEVICE_TABLE(of, img_ascii_lcd_matches);
220
221/**
222 * img_ascii_lcd_scroll() - scroll the display by a character
223 * @t: really a pointer to the private data structure
224 *
225 * Scroll the current message along the LCD by one character, rearming the
226 * timer if required.
227 */
228static void img_ascii_lcd_scroll(struct timer_list *t)
229{
230	struct img_ascii_lcd_ctx *ctx = from_timer(ctx, t, timer);
231	unsigned int i, ch = ctx->scroll_pos;
232	unsigned int num_chars = ctx->cfg->num_chars;
233
234	/* update the current message string */
235	for (i = 0; i < num_chars;) {
236		/* copy as many characters from the string as possible */
237		for (; i < num_chars && ch < ctx->message_len; i++, ch++)
238			ctx->curr[i] = ctx->message[ch];
239
240		/* wrap around to the start of the string */
241		ch = 0;
242	}
243
244	/* update the LCD */
245	ctx->cfg->update(ctx);
246
247	/* move on to the next character */
248	ctx->scroll_pos++;
249	ctx->scroll_pos %= ctx->message_len;
250
251	/* rearm the timer */
252	if (ctx->message_len > ctx->cfg->num_chars)
253		mod_timer(&ctx->timer, jiffies + ctx->scroll_rate);
254}
255
256/**
257 * img_ascii_lcd_display() - set the message to be displayed
258 * @ctx: pointer to the private data structure
259 * @msg: the message to display
260 * @count: length of msg, or -1
261 *
262 * Display a new message @msg on the LCD. @msg can be longer than the number of
263 * characters the LCD can display, in which case it will begin scrolling across
264 * the LCD display.
265 *
266 * Return: 0 on success, -ENOMEM on memory allocation failure
267 */
268static int img_ascii_lcd_display(struct img_ascii_lcd_ctx *ctx,
269			     const char *msg, ssize_t count)
270{
271	char *new_msg;
272
273	/* stop the scroll timer */
274	del_timer_sync(&ctx->timer);
275
276	if (count == -1)
277		count = strlen(msg);
278
279	/* if the string ends with a newline, trim it */
280	if (msg[count - 1] == '\n')
281		count--;
282
283	if (!count) {
284		/* clear the LCD */
285		devm_kfree(&ctx->pdev->dev, ctx->message);
286		ctx->message = NULL;
287		ctx->message_len = 0;
288		memset(ctx->curr, ' ', ctx->cfg->num_chars);
289		ctx->cfg->update(ctx);
290		return 0;
291	}
292
293	new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL);
294	if (!new_msg)
295		return -ENOMEM;
296
297	memcpy(new_msg, msg, count);
298	new_msg[count] = 0;
299
300	if (ctx->message)
301		devm_kfree(&ctx->pdev->dev, ctx->message);
302
303	ctx->message = new_msg;
304	ctx->message_len = count;
305	ctx->scroll_pos = 0;
306
307	/* update the LCD */
308	img_ascii_lcd_scroll(&ctx->timer);
309
310	return 0;
311}
312
313/**
314 * message_show() - read message via sysfs
315 * @dev: the LCD device
316 * @attr: the LCD message attribute
317 * @buf: the buffer to read the message into
318 *
319 * Read the current message being displayed or scrolled across the LCD display
320 * into @buf, for reads from sysfs.
321 *
322 * Return: the number of characters written to @buf
323 */
324static ssize_t message_show(struct device *dev, struct device_attribute *attr,
325			    char *buf)
326{
327	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
328
329	return sprintf(buf, "%s\n", ctx->message);
330}
331
332/**
333 * message_store() - write a new message via sysfs
334 * @dev: the LCD device
335 * @attr: the LCD message attribute
336 * @buf: the buffer containing the new message
337 * @count: the size of the message in @buf
338 *
339 * Write a new message to display or scroll across the LCD display from sysfs.
340 *
341 * Return: the size of the message on success, else -ERRNO
342 */
343static ssize_t message_store(struct device *dev, struct device_attribute *attr,
344			     const char *buf, size_t count)
345{
346	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
347	int err;
348
349	err = img_ascii_lcd_display(ctx, buf, count);
350	return err ?: count;
351}
352
353static DEVICE_ATTR_RW(message);
354
355/**
356 * img_ascii_lcd_probe() - probe an LCD display device
357 * @pdev: the LCD platform device
358 *
359 * Probe an LCD display device, ensuring that we have the required resources in
360 * order to access the LCD & setting up private data as well as sysfs files.
361 *
362 * Return: 0 on success, else -ERRNO
363 */
364static int img_ascii_lcd_probe(struct platform_device *pdev)
365{
366	const struct of_device_id *match;
367	const struct img_ascii_lcd_config *cfg;
368	struct img_ascii_lcd_ctx *ctx;
369	int err;
370
371	match = of_match_device(img_ascii_lcd_matches, &pdev->dev);
372	if (!match)
373		return -ENODEV;
374
375	cfg = match->data;
376	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx) + cfg->num_chars,
377			   GFP_KERNEL);
378	if (!ctx)
379		return -ENOMEM;
380
381	if (cfg->external_regmap) {
382		ctx->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
383		if (IS_ERR(ctx->regmap))
384			return PTR_ERR(ctx->regmap);
385
386		if (of_property_read_u32(pdev->dev.of_node, "offset",
387					 &ctx->offset))
388			return -EINVAL;
389	} else {
390		ctx->base = devm_platform_ioremap_resource(pdev, 0);
391		if (IS_ERR(ctx->base))
392			return PTR_ERR(ctx->base);
393	}
394
395	ctx->pdev = pdev;
396	ctx->cfg = cfg;
397	ctx->message = NULL;
398	ctx->scroll_pos = 0;
399	ctx->scroll_rate = HZ / 2;
400
401	/* initialise a timer for scrolling the message */
402	timer_setup(&ctx->timer, img_ascii_lcd_scroll, 0);
403
404	platform_set_drvdata(pdev, ctx);
405
406	/* display a default message */
407	err = img_ascii_lcd_display(ctx, "Linux " UTS_RELEASE "       ", -1);
408	if (err)
409		goto out_del_timer;
410
411	err = device_create_file(&pdev->dev, &dev_attr_message);
412	if (err)
413		goto out_del_timer;
414
415	return 0;
416out_del_timer:
417	del_timer_sync(&ctx->timer);
418	return err;
419}
420
421/**
422 * img_ascii_lcd_remove() - remove an LCD display device
423 * @pdev: the LCD platform device
424 *
425 * Remove an LCD display device, freeing private resources & ensuring that the
426 * driver stops using the LCD display registers.
427 *
428 * Return: 0
429 */
430static int img_ascii_lcd_remove(struct platform_device *pdev)
431{
432	struct img_ascii_lcd_ctx *ctx = platform_get_drvdata(pdev);
433
434	device_remove_file(&pdev->dev, &dev_attr_message);
435	del_timer_sync(&ctx->timer);
436	return 0;
437}
438
439static struct platform_driver img_ascii_lcd_driver = {
440	.driver = {
441		.name		= "img-ascii-lcd",
442		.of_match_table	= img_ascii_lcd_matches,
443	},
444	.probe	= img_ascii_lcd_probe,
445	.remove	= img_ascii_lcd_remove,
446};
447module_platform_driver(img_ascii_lcd_driver);
448
449MODULE_DESCRIPTION("Imagination Technologies ASCII LCD Display");
450MODULE_AUTHOR("Paul Burton <paul.burton@mips.com>");
451MODULE_LICENSE("GPL");
452