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/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  */
  64 struct 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
  74 static 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
  90 static 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
 113 static 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
 158 static 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
 173 static 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
 184 static 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
 195 static 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
 206 static 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
 231 static 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
 257 static 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
 265 static 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, "initialized ARM character LCD at %08x\n",
 317                 lcd->phybase);
 318
 319         return 0;
 320
 321 out_no_irq:
 322         iounmap(lcd->virtbase);
 323 out_no_remap:
 324         platform_set_drvdata(pdev, NULL);
 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 __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
 347 static 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
 357 static 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
 367 static const struct dev_pm_ops charlcd_pm_ops = {
 368         .suspend = charlcd_suspend,
 369         .resume = charlcd_resume,
 370 };
 371
 372 static 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
 381 module_platform_driver_probe(charlcd_driver, charlcd_probe);
 382
 383 MODULE_AUTHOR("Linus Walleij <triad@df.lth.se>");
 384 MODULE_DESCRIPTION("ARM Character LCD Driver");
 385 MODULE_LICENSE("GPL v2");