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	new_msg = devm_kmalloc(&ctx->pdev->dev, count + 1, GFP_KERNEL);
284	if (!new_msg)
285		return -ENOMEM;
286
287	memcpy(new_msg, msg, count);
288	new_msg[count] = 0;
289
290	if (ctx->message)
291		devm_kfree(&ctx->pdev->dev, ctx->message);
292
293	ctx->message = new_msg;
294	ctx->message_len = count;
295	ctx->scroll_pos = 0;
296
297	/* update the LCD */
298	img_ascii_lcd_scroll(&ctx->timer);
299
300	return 0;
301}
302
303/**
304 * message_show() - read message via sysfs
305 * @dev: the LCD device
306 * @attr: the LCD message attribute
307 * @buf: the buffer to read the message into
308 *
309 * Read the current message being displayed or scrolled across the LCD display
310 * into @buf, for reads from sysfs.
311 *
312 * Return: the number of characters written to @buf
313 */
314static ssize_t message_show(struct device *dev, struct device_attribute *attr,
315			    char *buf)
316{
317	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
318
319	return sprintf(buf, "%s\n", ctx->message);
320}
321
322/**
323 * message_store() - write a new message via sysfs
324 * @dev: the LCD device
325 * @attr: the LCD message attribute
326 * @buf: the buffer containing the new message
327 * @count: the size of the message in @buf
328 *
329 * Write a new message to display or scroll across the LCD display from sysfs.
330 *
331 * Return: the size of the message on success, else -ERRNO
332 */
333static ssize_t message_store(struct device *dev, struct device_attribute *attr,
334			     const char *buf, size_t count)
335{
336	struct img_ascii_lcd_ctx *ctx = dev_get_drvdata(dev);
337	int err;
338
339	err = img_ascii_lcd_display(ctx, buf, count);
340	return err ?: count;
341}
342
343static DEVICE_ATTR_RW(message);
344
345/**
346 * img_ascii_lcd_probe() - probe an LCD display device
347 * @pdev: the LCD platform device
348 *
349 * Probe an LCD display device, ensuring that we have the required resources in
350 * order to access the LCD & setting up private data as well as sysfs files.
351 *
352 * Return: 0 on success, else -ERRNO
353 */
354static int img_ascii_lcd_probe(struct platform_device *pdev)
355{
356	const struct of_device_id *match;
357	const struct img_ascii_lcd_config *cfg;
358	struct img_ascii_lcd_ctx *ctx;
359	int err;
360
361	match = of_match_device(img_ascii_lcd_matches, &pdev->dev);
362	if (!match)
363		return -ENODEV;
364
365	cfg = match->data;
366	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx) + cfg->num_chars,
367			   GFP_KERNEL);
368	if (!ctx)
369		return -ENOMEM;
370
371	if (cfg->external_regmap) {
372		ctx->regmap = syscon_node_to_regmap(pdev->dev.parent->of_node);
373		if (IS_ERR(ctx->regmap))
374			return PTR_ERR(ctx->regmap);
375
376		if (of_property_read_u32(pdev->dev.of_node, "offset",
377					 &ctx->offset))
378			return -EINVAL;
379	} else {
380		ctx->base = devm_platform_ioremap_resource(pdev, 0);
381		if (IS_ERR(ctx->base))
382			return PTR_ERR(ctx->base);
383	}
384
385	ctx->pdev = pdev;
386	ctx->cfg = cfg;
387	ctx->message = NULL;
388	ctx->scroll_pos = 0;
389	ctx->scroll_rate = HZ / 2;
390
391	/* initialise a timer for scrolling the message */
392	timer_setup(&ctx->timer, img_ascii_lcd_scroll, 0);
393
394	platform_set_drvdata(pdev, ctx);
395
396	/* display a default message */
397	err = img_ascii_lcd_display(ctx, "Linux " UTS_RELEASE "       ", -1);
398	if (err)
399		goto out_del_timer;
400
401	err = device_create_file(&pdev->dev, &dev_attr_message);
402	if (err)
403		goto out_del_timer;
404
405	return 0;
406out_del_timer:
407	del_timer_sync(&ctx->timer);
408	return err;
409}
410
411/**
412 * img_ascii_lcd_remove() - remove an LCD display device
413 * @pdev: the LCD platform device
414 *
415 * Remove an LCD display device, freeing private resources & ensuring that the
416 * driver stops using the LCD display registers.
417 *
418 * Return: 0
419 */
420static int img_ascii_lcd_remove(struct platform_device *pdev)
421{
422	struct img_ascii_lcd_ctx *ctx = platform_get_drvdata(pdev);
423
424	device_remove_file(&pdev->dev, &dev_attr_message);
425	del_timer_sync(&ctx->timer);
426	return 0;
427}
428
429static struct platform_driver img_ascii_lcd_driver = {
430	.driver = {
431		.name		= "img-ascii-lcd",
432		.of_match_table	= img_ascii_lcd_matches,
433	},
434	.probe	= img_ascii_lcd_probe,
435	.remove	= img_ascii_lcd_remove,
436};
437module_platform_driver(img_ascii_lcd_driver);
438
439MODULE_DESCRIPTION("Imagination Technologies ASCII LCD Display");
440MODULE_AUTHOR("Paul Burton <paul.burton@mips.com>");
441MODULE_LICENSE("GPL");