drivers/auxdisplay/arm-charlcd.c

   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  * https://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);