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 * http://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 <triad@df.lth.se> 9 */ 10 #include <linux/init.h> 11 #include <linux/interrupt.h> 12 #include <linux/platform_device.h> 13 #include <linux/of.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 * struct charlcd - Private data structure 58 * @dev: a pointer back to containing device 59 * @phybase: the offset to the controller in physical memory 60 * @physize: the size of the physical page 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 */ 66 struct charlcd { 67 struct device *dev; 68 u32 phybase; 69 u32 physize; 70 void __iomem *virtbase; 71 int irq; 72 struct completion complete; 73 struct delayed_work init_work; 74 }; 75 76 static irqreturn_t charlcd_interrupt(int irq, void *data) 77 { 78 struct charlcd *lcd = data; 79 u8 status; 80 81 status = readl(lcd->virtbase + CHAR_STAT) & 0x01; 82 /* Clear IRQ */ 83 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); 84 if (status) 85 complete(&lcd->complete); 86 else 87 dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status); 88 return IRQ_HANDLED; 89 } 90 91 92 static void charlcd_wait_complete_irq(struct charlcd *lcd) 93 { 94 int ret; 95 96 ret = wait_for_completion_interruptible_timeout(&lcd->complete, 97 CHARLCD_TIMEOUT); 98 /* Disable IRQ after completion */ 99 writel(0x00, lcd->virtbase + CHAR_MASK); 100 101 if (ret < 0) { 102 dev_err(lcd->dev, 103 "wait_for_completion_interruptible_timeout() " 104 "returned %d waiting for ready\n", ret); 105 return; 106 } 107 108 if (ret == 0) { 109 dev_err(lcd->dev, "charlcd controller timed out " 110 "waiting for ready\n"); 111 return; 112 } 113 } 114 115 static u8 charlcd_4bit_read_char(struct charlcd *lcd) 116 { 117 u8 data; 118 u32 val; 119 int i; 120 121 /* If we can, use an IRQ to wait for the data, else poll */ 122 if (lcd->irq >= 0) 123 charlcd_wait_complete_irq(lcd); 124 else { 125 i = 0; 126 val = 0; 127 while (!(val & CHAR_RAW_VALID) && i < 10) { 128 udelay(100); 129 val = readl(lcd->virtbase + CHAR_RAW); 130 i++; 131 } 132 133 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); 134 } 135 msleep(1); 136 137 /* Read the 4 high bits of the data */ 138 data = readl(lcd->virtbase + CHAR_RD) & 0xf0; 139 140 /* 141 * The second read for the low bits does not trigger an IRQ 142 * so in this case we have to poll for the 4 lower bits 143 */ 144 i = 0; 145 val = 0; 146 while (!(val & CHAR_RAW_VALID) && i < 10) { 147 udelay(100); 148 val = readl(lcd->virtbase + CHAR_RAW); 149 i++; 150 } 151 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); 152 msleep(1); 153 154 /* Read the 4 low bits of the data */ 155 data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f; 156 157 return data; 158 } 159 160 static bool charlcd_4bit_read_bf(struct charlcd *lcd) 161 { 162 if (lcd->irq >= 0) { 163 /* 164 * If we'll use IRQs to wait for the busyflag, clear any 165 * pending flag and enable IRQ 166 */ 167 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); 168 init_completion(&lcd->complete); 169 writel(0x01, lcd->virtbase + CHAR_MASK); 170 } 171 readl(lcd->virtbase + CHAR_COM); 172 return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false; 173 } 174 175 static void charlcd_4bit_wait_busy(struct charlcd *lcd) 176 { 177 int retries = 50; 178 179 udelay(100); 180 while (charlcd_4bit_read_bf(lcd) && retries) 181 retries--; 182 if (!retries) 183 dev_err(lcd->dev, "timeout waiting for busyflag\n"); 184 } 185 186 static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd) 187 { 188 u32 cmdlo = (cmd << 4) & 0xf0; 189 u32 cmdhi = (cmd & 0xf0); 190 191 writel(cmdhi, lcd->virtbase + CHAR_COM); 192 udelay(10); 193 writel(cmdlo, lcd->virtbase + CHAR_COM); 194 charlcd_4bit_wait_busy(lcd); 195 } 196 197 static void charlcd_4bit_char(struct charlcd *lcd, u8 ch) 198 { 199 u32 chlo = (ch << 4) & 0xf0; 200 u32 chhi = (ch & 0xf0); 201 202 writel(chhi, lcd->virtbase + CHAR_DAT); 203 udelay(10); 204 writel(chlo, lcd->virtbase + CHAR_DAT); 205 charlcd_4bit_wait_busy(lcd); 206 } 207 208 static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str) 209 { 210 u8 offset; 211 int i; 212 213 /* 214 * We support line 0, 1 215 * Line 1 runs from 0x00..0x27 216 * Line 2 runs from 0x28..0x4f 217 */ 218 if (line == 0) 219 offset = 0; 220 else if (line == 1) 221 offset = 0x28; 222 else 223 return; 224 225 /* Set offset */ 226 charlcd_4bit_command(lcd, HD_SET_DDRAM | offset); 227 228 /* Send string */ 229 for (i = 0; i < strlen(str) && i < 0x28; i++) 230 charlcd_4bit_char(lcd, str[i]); 231 } 232 233 static void charlcd_4bit_init(struct charlcd *lcd) 234 { 235 /* These commands cannot be checked with the busy flag */ 236 writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); 237 msleep(5); 238 writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); 239 udelay(100); 240 writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); 241 udelay(100); 242 /* Go to 4bit mode */ 243 writel(HD_FUNCSET, lcd->virtbase + CHAR_COM); 244 udelay(100); 245 /* 246 * 4bit mode, 2 lines, 5x8 font, after this the number of lines 247 * and the font cannot be changed until the next initialization sequence 248 */ 249 charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES); 250 charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON); 251 charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT); 252 charlcd_4bit_command(lcd, HD_CLEAR); 253 charlcd_4bit_command(lcd, HD_HOME); 254 /* Put something useful in the display */ 255 charlcd_4bit_print(lcd, 0, "ARM Linux"); 256 charlcd_4bit_print(lcd, 1, UTS_RELEASE); 257 } 258 259 static void charlcd_init_work(struct work_struct *work) 260 { 261 struct charlcd *lcd = 262 container_of(work, struct charlcd, init_work.work); 263 264 charlcd_4bit_init(lcd); 265 } 266 267 static int __init charlcd_probe(struct platform_device *pdev) 268 { 269 int ret; 270 struct charlcd *lcd; 271 struct resource *res; 272 273 lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL); 274 if (!lcd) 275 return -ENOMEM; 276 277 lcd->dev = &pdev->dev; 278 279 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 280 if (!res) { 281 ret = -ENOENT; 282 goto out_no_resource; 283 } 284 lcd->phybase = res->start; 285 lcd->physize = resource_size(res); 286 287 if (request_mem_region(lcd->phybase, lcd->physize, 288 DRIVERNAME) == NULL) { 289 ret = -EBUSY; 290 goto out_no_memregion; 291 } 292 293 lcd->virtbase = ioremap(lcd->phybase, lcd->physize); 294 if (!lcd->virtbase) { 295 ret = -ENOMEM; 296 goto out_no_memregion; 297 } 298 299 lcd->irq = platform_get_irq(pdev, 0); 300 /* If no IRQ is supplied, we'll survive without it */ 301 if (lcd->irq >= 0) { 302 if (request_irq(lcd->irq, charlcd_interrupt, 0, 303 DRIVERNAME, lcd)) { 304 ret = -EIO; 305 goto out_no_irq; 306 } 307 } 308 309 platform_set_drvdata(pdev, lcd); 310 311 /* 312 * Initialize the display in a delayed work, because 313 * it is VERY slow and would slow down the boot of the system. 314 */ 315 INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work); 316 schedule_delayed_work(&lcd->init_work, 0); 317 318 dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n", 319 lcd->phybase); 320 321 return 0; 322 323 out_no_irq: 324 iounmap(lcd->virtbase); 325 out_no_memregion: 326 release_mem_region(lcd->phybase, SZ_4K); 327 out_no_resource: 328 kfree(lcd); 329 return ret; 330 } 331 332 static int charlcd_suspend(struct device *dev) 333 { 334 struct charlcd *lcd = dev_get_drvdata(dev); 335 336 /* Power the display off */ 337 charlcd_4bit_command(lcd, HD_DISPCTRL); 338 return 0; 339 } 340 341 static int charlcd_resume(struct device *dev) 342 { 343 struct charlcd *lcd = dev_get_drvdata(dev); 344 345 /* Turn the display back on */ 346 charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON); 347 return 0; 348 } 349 350 static const struct dev_pm_ops charlcd_pm_ops = { 351 .suspend = charlcd_suspend, 352 .resume = charlcd_resume, 353 }; 354 355 static const struct of_device_id charlcd_match[] = { 356 { .compatible = "arm,versatile-lcd", }, 357 {} 358 }; 359 360 static struct platform_driver charlcd_driver = { 361 .driver = { 362 .name = DRIVERNAME, 363 .pm = &charlcd_pm_ops, 364 .suppress_bind_attrs = true, 365 .of_match_table = of_match_ptr(charlcd_match), 366 }, 367 }; 368 builtin_platform_driver_probe(charlcd_driver, charlcd_probe); 369