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, "initalized 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