drivers/misc/arm-charlcd.c

   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/of.h>
  15 #include <linux/completion.h>
  16 #include <linux/delay.h>
  17 #include <linux/io.h>
  18 #include <linux/slab.h>
  19 #include <linux/workqueue.h>
  20 #include <generated/utsrelease.h>
  21
  22 #define DRIVERNAME "arm-charlcd"
  23 #define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
  24
  25 /* Offsets to registers */
  26 #define CHAR_COM        0x00U
  27 #define CHAR_DAT        0x04U
  28 #define CHAR_RD         0x08U
  29 #define CHAR_RAW        0x0CU
  30 #define CHAR_MASK       0x10U
  31 #define CHAR_STAT       0x14U
  32
  33 #define CHAR_RAW_CLEAR  0x00000000U
  34 #define CHAR_RAW_VALID  0x00000100U
  35
  36 /* Hitachi HD44780 display commands */
  37 #define HD_CLEAR                        0x01U
  38 #define HD_HOME                         0x02U
  39 #define HD_ENTRYMODE                    0x04U
  40 #define HD_ENTRYMODE_INCREMENT          0x02U
  41 #define HD_ENTRYMODE_SHIFT              0x01U
  42 #define HD_DISPCTRL                     0x08U
  43 #define HD_DISPCTRL_ON                  0x04U
  44 #define HD_DISPCTRL_CURSOR_ON           0x02U
  45 #define HD_DISPCTRL_CURSOR_BLINK        0x01U
  46 #define HD_CRSR_SHIFT                   0x10U
  47 #define HD_CRSR_SHIFT_DISPLAY           0x08U
  48 #define HD_CRSR_SHIFT_DISPLAY_RIGHT     0x04U
  49 #define HD_FUNCSET                      0x20U
  50 #define HD_FUNCSET_8BIT                 0x10U
  51 #define HD_FUNCSET_2_LINES              0x08U
  52 #define HD_FUNCSET_FONT_5X10            0x04U
  53 #define HD_SET_CGRAM                    0x40U
  54 #define HD_SET_DDRAM                    0x80U
  55 #define HD_BUSY_FLAG                    0x80U
  56
  57 /**
  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  */
  65 struct charlcd {
  66         struct device *dev;
  67         u32 phybase;
  68         u32 physize;
  69         void __iomem *virtbase;
  70         int irq;
  71         struct completion complete;
  72         struct delayed_work init_work;
  73 };
  74
  75 static irqreturn_t charlcd_interrupt(int irq, void *data)
  76 {
  77         struct charlcd *lcd = data;
  78         u8 status;
  79
  80         status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
  81         /* Clear IRQ */
  82         writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
  83         if (status)
  84                 complete(&lcd->complete);
  85         else
  86                 dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status);
  87         return IRQ_HANDLED;
  88 }
  89
  90
  91 static void charlcd_wait_complete_irq(struct charlcd *lcd)
  92 {
  93         int ret;
  94
  95         ret = wait_for_completion_interruptible_timeout(&lcd->complete,
  96                                                         CHARLCD_TIMEOUT);
  97         /* Disable IRQ after completion */
  98         writel(0x00, lcd->virtbase + CHAR_MASK);
  99
 100         if (ret < 0) {
 101                 dev_err(lcd->dev,
 102                         "wait_for_completion_interruptible_timeout() "
 103                         "returned %d waiting for ready\n", ret);
 104                 return;
 105         }
 106
 107         if (ret == 0) {
 108                 dev_err(lcd->dev, "charlcd controller timed out "
 109                         "waiting for ready\n");
 110                 return;
 111         }
 112 }
 113
 114 static u8 charlcd_4bit_read_char(struct charlcd *lcd)
 115 {
 116         u8 data;
 117         u32 val;
 118         int i;
 119
 120         /* If we can, use an IRQ to wait for the data, else poll */
 121         if (lcd->irq >= 0)
 122                 charlcd_wait_complete_irq(lcd);
 123         else {
 124                 i = 0;
 125                 val = 0;
 126                 while (!(val & CHAR_RAW_VALID) && i < 10) {
 127                         udelay(100);
 128                         val = readl(lcd->virtbase + CHAR_RAW);
 129                         i++;
 130                 }
 131
 132                 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
 133         }
 134         msleep(1);
 135
 136         /* Read the 4 high bits of the data */
 137         data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
 138
 139         /*
 140          * The second read for the low bits does not trigger an IRQ
 141          * so in this case we have to poll for the 4 lower bits
 142          */
 143         i = 0;
 144         val = 0;
 145         while (!(val & CHAR_RAW_VALID) && i < 10) {
 146                 udelay(100);
 147                 val = readl(lcd->virtbase + CHAR_RAW);
 148                 i++;
 149         }
 150         writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
 151         msleep(1);
 152
 153         /* Read the 4 low bits of the data */
 154         data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
 155
 156         return data;
 157 }
 158
 159 static bool charlcd_4bit_read_bf(struct charlcd *lcd)
 160 {
 161         if (lcd->irq >= 0) {
 162                 /*
 163                  * If we'll use IRQs to wait for the busyflag, clear any
 164                  * pending flag and enable IRQ
 165                  */
 166                 writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
 167                 init_completion(&lcd->complete);
 168                 writel(0x01, lcd->virtbase + CHAR_MASK);
 169         }
 170         readl(lcd->virtbase + CHAR_COM);
 171         return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false;
 172 }
 173
 174 static void charlcd_4bit_wait_busy(struct charlcd *lcd)
 175 {
 176         int retries = 50;
 177
 178         udelay(100);
 179         while (charlcd_4bit_read_bf(lcd) && retries)
 180                 retries--;
 181         if (!retries)
 182                 dev_err(lcd->dev, "timeout waiting for busyflag\n");
 183 }
 184
 185 static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
 186 {
 187         u32 cmdlo = (cmd << 4) & 0xf0;
 188         u32 cmdhi = (cmd & 0xf0);
 189
 190         writel(cmdhi, lcd->virtbase + CHAR_COM);
 191         udelay(10);
 192         writel(cmdlo, lcd->virtbase + CHAR_COM);
 193         charlcd_4bit_wait_busy(lcd);
 194 }
 195
 196 static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
 197 {
 198         u32 chlo = (ch << 4) & 0xf0;
 199         u32 chhi = (ch & 0xf0);
 200
 201         writel(chhi, lcd->virtbase + CHAR_DAT);
 202         udelay(10);
 203         writel(chlo, lcd->virtbase + CHAR_DAT);
 204         charlcd_4bit_wait_busy(lcd);
 205 }
 206
 207 static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
 208 {
 209         u8 offset;
 210         int i;
 211
 212         /*
 213          * We support line 0, 1
 214          * Line 1 runs from 0x00..0x27
 215          * Line 2 runs from 0x28..0x4f
 216          */
 217         if (line == 0)
 218                 offset = 0;
 219         else if (line == 1)
 220                 offset = 0x28;
 221         else
 222                 return;
 223
 224         /* Set offset */
 225         charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
 226
 227         /* Send string */
 228         for (i = 0; i < strlen(str) && i < 0x28; i++)
 229                 charlcd_4bit_char(lcd, str[i]);
 230 }
 231
 232 static void charlcd_4bit_init(struct charlcd *lcd)
 233 {
 234         /* These commands cannot be checked with the busy flag */
 235         writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
 236         msleep(5);
 237         writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
 238         udelay(100);
 239         writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
 240         udelay(100);
 241         /* Go to 4bit mode */
 242         writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
 243         udelay(100);
 244         /*
 245          * 4bit mode, 2 lines, 5x8 font, after this the number of lines
 246          * and the font cannot be changed until the next initialization sequence
 247          */
 248         charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
 249         charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
 250         charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
 251         charlcd_4bit_command(lcd, HD_CLEAR);
 252         charlcd_4bit_command(lcd, HD_HOME);
 253         /* Put something useful in the display */
 254         charlcd_4bit_print(lcd, 0, "ARM Linux");
 255         charlcd_4bit_print(lcd, 1, UTS_RELEASE);
 256 }
 257
 258 static void charlcd_init_work(struct work_struct *work)
 259 {
 260         struct charlcd *lcd =
 261                 container_of(work, struct charlcd, init_work.work);
 262
 263         charlcd_4bit_init(lcd);
 264 }
 265
 266 static int __init charlcd_probe(struct platform_device *pdev)
 267 {
 268         int ret;
 269         struct charlcd *lcd;
 270         struct resource *res;
 271
 272         lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL);
 273         if (!lcd)
 274                 return -ENOMEM;
 275
 276         lcd->dev = &pdev->dev;
 277
 278         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 279         if (!res) {
 280                 ret = -ENOENT;
 281                 goto out_no_resource;
 282         }
 283         lcd->phybase = res->start;
 284         lcd->physize = resource_size(res);
 285
 286         if (request_mem_region(lcd->phybase, lcd->physize,
 287                                DRIVERNAME) == NULL) {
 288                 ret = -EBUSY;
 289                 goto out_no_memregion;
 290         }
 291
 292         lcd->virtbase = ioremap(lcd->phybase, lcd->physize);
 293         if (!lcd->virtbase) {
 294                 ret = -ENOMEM;
 295                 goto out_no_memregion;
 296         }
 297
 298         lcd->irq = platform_get_irq(pdev, 0);
 299         /* If no IRQ is supplied, we'll survive without it */
 300         if (lcd->irq >= 0) {
 301                 if (request_irq(lcd->irq, charlcd_interrupt, 0,
 302                                 DRIVERNAME, lcd)) {
 303                         ret = -EIO;
 304                         goto out_no_irq;
 305                 }
 306         }
 307
 308         platform_set_drvdata(pdev, lcd);
 309
 310         /*
 311          * Initialize the display in a delayed work, because
 312          * it is VERY slow and would slow down the boot of the system.
 313          */
 314         INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
 315         schedule_delayed_work(&lcd->init_work, 0);
 316
 317         dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n",
 318                 lcd->phybase);
 319
 320         return 0;
 321
 322 out_no_irq:
 323         iounmap(lcd->virtbase);
 324 out_no_memregion:
 325         release_mem_region(lcd->phybase, SZ_4K);
 326 out_no_resource:
 327         kfree(lcd);
 328         return ret;
 329 }
 330
 331 static int __exit charlcd_remove(struct platform_device *pdev)
 332 {
 333         struct charlcd *lcd = platform_get_drvdata(pdev);
 334
 335         if (lcd) {
 336                 free_irq(lcd->irq, lcd);
 337                 iounmap(lcd->virtbase);
 338                 release_mem_region(lcd->phybase, lcd->physize);
 339                 kfree(lcd);
 340         }
 341
 342         return 0;
 343 }
 344
 345 static int charlcd_suspend(struct device *dev)
 346 {
 347         struct platform_device *pdev = to_platform_device(dev);
 348         struct charlcd *lcd = platform_get_drvdata(pdev);
 349
 350         /* Power the display off */
 351         charlcd_4bit_command(lcd, HD_DISPCTRL);
 352         return 0;
 353 }
 354
 355 static int charlcd_resume(struct device *dev)
 356 {
 357         struct platform_device *pdev = to_platform_device(dev);
 358         struct charlcd *lcd = platform_get_drvdata(pdev);
 359
 360         /* Turn the display back on */
 361         charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
 362         return 0;
 363 }
 364
 365 static const struct dev_pm_ops charlcd_pm_ops = {
 366         .suspend = charlcd_suspend,
 367         .resume = charlcd_resume,
 368 };
 369
 370 static const struct of_device_id charlcd_match[] = {
 371         { .compatible = "arm,versatile-lcd", },
 372         {}
 373 };
 374
 375 static struct platform_driver charlcd_driver = {
 376         .driver = {
 377                 .name = DRIVERNAME,
 378                 .owner = THIS_MODULE,
 379                 .pm = &charlcd_pm_ops,
 380                 .of_match_table = of_match_ptr(charlcd_match),
 381         },
 382         .remove = __exit_p(charlcd_remove),
 383 };
 384
 385 module_platform_driver_probe(charlcd_driver, charlcd_probe);
 386
 387 MODULE_AUTHOR("Linus Walleij <triad@df.lth.se>");
 388 MODULE_DESCRIPTION("ARM Character LCD Driver");
 389 MODULE_LICENSE("GPL v2");