LXR linux/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 */
  66struct 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
  76static 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
  92static 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
 115static 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
 160static 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
 175static 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
 186static 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
 197static 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
 208static 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
 233static 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
 259static 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
 267static 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
 323out_no_irq:
 324        iounmap(lcd->virtbase);
 325out_no_memregion:
 326        release_mem_region(lcd->phybase, SZ_4K);
 327out_no_resource:
 328        kfree(lcd);
 329        return ret;
 330}
 331
 332static 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
 341static 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
 350static const struct dev_pm_ops charlcd_pm_ops = {
 351        .suspend = charlcd_suspend,
 352        .resume = charlcd_resume,
 353};
 354
 355static const struct of_device_id charlcd_match[] = {
 356        { .compatible = "arm,versatile-lcd", },
 357        {}
 358};
 359
 360static 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};
 368builtin_platform_driver_probe(charlcd_driver, charlcd_probe);
 369