drivers/auxdisplay/arm-charlcd.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Driver for the on-board character LCD found on some ARM reference boards
0004  * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it
0005  * https://en.wikipedia.org/wiki/HD44780_Character_LCD
0006  * Currently it will just display the text "ARM Linux" and the linux version
0007  *
0008  * Author: Linus Walleij <triad@df.lth.se>
0009  */
0010 #include <linux/init.h>
0011 #include <linux/interrupt.h>
0012 #include <linux/platform_device.h>
0013 #include <linux/of.h>
0014 #include <linux/completion.h>
0015 #include <linux/delay.h>
0016 #include <linux/io.h>
0017 #include <linux/slab.h>
0018 #include <linux/workqueue.h>
0019 #include <generated/utsrelease.h>
0020
0021 #define DRIVERNAME "arm-charlcd"
0022 #define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
0023
0024 /* Offsets to registers */
0025 #define CHAR_COM    0x00U
0026 #define CHAR_DAT    0x04U
0027 #define CHAR_RD     0x08U
0028 #define CHAR_RAW    0x0CU
0029 #define CHAR_MASK   0x10U
0030 #define CHAR_STAT   0x14U
0031
0032 #define CHAR_RAW_CLEAR  0x00000000U
0033 #define CHAR_RAW_VALID  0x00000100U
0034
0035 /* Hitachi HD44780 display commands */
0036 #define HD_CLEAR            0x01U
0037 #define HD_HOME             0x02U
0038 #define HD_ENTRYMODE            0x04U
0039 #define HD_ENTRYMODE_INCREMENT      0x02U
0040 #define HD_ENTRYMODE_SHIFT      0x01U
0041 #define HD_DISPCTRL         0x08U
0042 #define HD_DISPCTRL_ON          0x04U
0043 #define HD_DISPCTRL_CURSOR_ON       0x02U
0044 #define HD_DISPCTRL_CURSOR_BLINK    0x01U
0045 #define HD_CRSR_SHIFT           0x10U
0046 #define HD_CRSR_SHIFT_DISPLAY       0x08U
0047 #define HD_CRSR_SHIFT_DISPLAY_RIGHT 0x04U
0048 #define HD_FUNCSET          0x20U
0049 #define HD_FUNCSET_8BIT         0x10U
0050 #define HD_FUNCSET_2_LINES      0x08U
0051 #define HD_FUNCSET_FONT_5X10        0x04U
0052 #define HD_SET_CGRAM            0x40U
0053 #define HD_SET_DDRAM            0x80U
0054 #define HD_BUSY_FLAG            0x80U
0055
0056 /**
0057  * struct charlcd - Private data structure
0058  * @dev: a pointer back to containing device
0059  * @phybase: the offset to the controller in physical memory
0060  * @physize: the size of the physical page
0061  * @virtbase: the offset to the controller in virtual memory
0062  * @irq: reserved interrupt number
0063  * @complete: completion structure for the last LCD command
0064  * @init_work: delayed work structure to initialize the display on boot
0065  */
0066 struct charlcd {
0067     struct device *dev;
0068     u32 phybase;
0069     u32 physize;
0070     void __iomem *virtbase;
0071     int irq;
0072     struct completion complete;
0073     struct delayed_work init_work;
0074 };
0075
0076 static irqreturn_t charlcd_interrupt(int irq, void *data)
0077 {
0078     struct charlcd *lcd = data;
0079     u8 status;
0080
0081     status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
0082     /* Clear IRQ */
0083     writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
0084     if (status)
0085         complete(&lcd->complete);
0086     else
0087         dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status);
0088     return IRQ_HANDLED;
0089 }
0090
0091
0092 static void charlcd_wait_complete_irq(struct charlcd *lcd)
0093 {
0094     int ret;
0095
0096     ret = wait_for_completion_interruptible_timeout(&lcd->complete,
0097                             CHARLCD_TIMEOUT);
0098     /* Disable IRQ after completion */
0099     writel(0x00, lcd->virtbase + CHAR_MASK);
0100
0101     if (ret < 0) {
0102         dev_err(lcd->dev,
0103             "wait_for_completion_interruptible_timeout() "
0104             "returned %d waiting for ready\n", ret);
0105         return;
0106     }
0107
0108     if (ret == 0) {
0109         dev_err(lcd->dev, "charlcd controller timed out "
0110             "waiting for ready\n");
0111         return;
0112     }
0113 }
0114
0115 static u8 charlcd_4bit_read_char(struct charlcd *lcd)
0116 {
0117     u8 data;
0118     u32 val;
0119     int i;
0120
0121     /* If we can, use an IRQ to wait for the data, else poll */
0122     if (lcd->irq >= 0)
0123         charlcd_wait_complete_irq(lcd);
0124     else {
0125         i = 0;
0126         val = 0;
0127         while (!(val & CHAR_RAW_VALID) && i < 10) {
0128             udelay(100);
0129             val = readl(lcd->virtbase + CHAR_RAW);
0130             i++;
0131         }
0132
0133         writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
0134     }
0135     msleep(1);
0136
0137     /* Read the 4 high bits of the data */
0138     data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
0139
0140     /*
0141      * The second read for the low bits does not trigger an IRQ
0142      * so in this case we have to poll for the 4 lower bits
0143      */
0144     i = 0;
0145     val = 0;
0146     while (!(val & CHAR_RAW_VALID) && i < 10) {
0147         udelay(100);
0148         val = readl(lcd->virtbase + CHAR_RAW);
0149         i++;
0150     }
0151     writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
0152     msleep(1);
0153
0154     /* Read the 4 low bits of the data */
0155     data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
0156
0157     return data;
0158 }
0159
0160 static bool charlcd_4bit_read_bf(struct charlcd *lcd)
0161 {
0162     if (lcd->irq >= 0) {
0163         /*
0164          * If we'll use IRQs to wait for the busyflag, clear any
0165          * pending flag and enable IRQ
0166          */
0167         writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
0168         init_completion(&lcd->complete);
0169         writel(0x01, lcd->virtbase + CHAR_MASK);
0170     }
0171     readl(lcd->virtbase + CHAR_COM);
0172     return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false;
0173 }
0174
0175 static void charlcd_4bit_wait_busy(struct charlcd *lcd)
0176 {
0177     int retries = 50;
0178
0179     udelay(100);
0180     while (charlcd_4bit_read_bf(lcd) && retries)
0181         retries--;
0182     if (!retries)
0183         dev_err(lcd->dev, "timeout waiting for busyflag\n");
0184 }
0185
0186 static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
0187 {
0188     u32 cmdlo = (cmd << 4) & 0xf0;
0189     u32 cmdhi = (cmd & 0xf0);
0190
0191     writel(cmdhi, lcd->virtbase + CHAR_COM);
0192     udelay(10);
0193     writel(cmdlo, lcd->virtbase + CHAR_COM);
0194     charlcd_4bit_wait_busy(lcd);
0195 }
0196
0197 static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
0198 {
0199     u32 chlo = (ch << 4) & 0xf0;
0200     u32 chhi = (ch & 0xf0);
0201
0202     writel(chhi, lcd->virtbase + CHAR_DAT);
0203     udelay(10);
0204     writel(chlo, lcd->virtbase + CHAR_DAT);
0205     charlcd_4bit_wait_busy(lcd);
0206 }
0207
0208 static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
0209 {
0210     u8 offset;
0211     int i;
0212
0213     /*
0214      * We support line 0, 1
0215      * Line 1 runs from 0x00..0x27
0216      * Line 2 runs from 0x28..0x4f
0217      */
0218     if (line == 0)
0219         offset = 0;
0220     else if (line == 1)
0221         offset = 0x28;
0222     else
0223         return;
0224
0225     /* Set offset */
0226     charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
0227
0228     /* Send string */
0229     for (i = 0; i < strlen(str) && i < 0x28; i++)
0230         charlcd_4bit_char(lcd, str[i]);
0231 }
0232
0233 static void charlcd_4bit_init(struct charlcd *lcd)
0234 {
0235     /* These commands cannot be checked with the busy flag */
0236     writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
0237     msleep(5);
0238     writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
0239     udelay(100);
0240     writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
0241     udelay(100);
0242     /* Go to 4bit mode */
0243     writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
0244     udelay(100);
0245     /*
0246      * 4bit mode, 2 lines, 5x8 font, after this the number of lines
0247      * and the font cannot be changed until the next initialization sequence
0248      */
0249     charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
0250     charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
0251     charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
0252     charlcd_4bit_command(lcd, HD_CLEAR);
0253     charlcd_4bit_command(lcd, HD_HOME);
0254     /* Put something useful in the display */
0255     charlcd_4bit_print(lcd, 0, "ARM Linux");
0256     charlcd_4bit_print(lcd, 1, UTS_RELEASE);
0257 }
0258
0259 static void charlcd_init_work(struct work_struct *work)
0260 {
0261     struct charlcd *lcd =
0262         container_of(work, struct charlcd, init_work.work);
0263
0264     charlcd_4bit_init(lcd);
0265 }
0266
0267 static int __init charlcd_probe(struct platform_device *pdev)
0268 {
0269     int ret;
0270     struct charlcd *lcd;
0271     struct resource *res;
0272
0273     lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL);
0274     if (!lcd)
0275         return -ENOMEM;
0276
0277     lcd->dev = &pdev->dev;
0278
0279     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
0280     if (!res) {
0281         ret = -ENOENT;
0282         goto out_no_resource;
0283     }
0284     lcd->phybase = res->start;
0285     lcd->physize = resource_size(res);
0286
0287     if (request_mem_region(lcd->phybase, lcd->physize,
0288                    DRIVERNAME) == NULL) {
0289         ret = -EBUSY;
0290         goto out_no_memregion;
0291     }
0292
0293     lcd->virtbase = ioremap(lcd->phybase, lcd->physize);
0294     if (!lcd->virtbase) {
0295         ret = -ENOMEM;
0296         goto out_no_memregion;
0297     }
0298
0299     lcd->irq = platform_get_irq(pdev, 0);
0300     /* If no IRQ is supplied, we'll survive without it */
0301     if (lcd->irq >= 0) {
0302         if (request_irq(lcd->irq, charlcd_interrupt, 0,
0303                 DRIVERNAME, lcd)) {
0304             ret = -EIO;
0305             goto out_no_irq;
0306         }
0307     }
0308
0309     platform_set_drvdata(pdev, lcd);
0310
0311     /*
0312      * Initialize the display in a delayed work, because
0313      * it is VERY slow and would slow down the boot of the system.
0314      */
0315     INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
0316     schedule_delayed_work(&lcd->init_work, 0);
0317
0318     dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n",
0319         lcd->phybase);
0320
0321     return 0;
0322
0323 out_no_irq:
0324     iounmap(lcd->virtbase);
0325 out_no_memregion:
0326     release_mem_region(lcd->phybase, SZ_4K);
0327 out_no_resource:
0328     kfree(lcd);
0329     return ret;
0330 }
0331
0332 static int charlcd_suspend(struct device *dev)
0333 {
0334     struct charlcd *lcd = dev_get_drvdata(dev);
0335
0336     /* Power the display off */
0337     charlcd_4bit_command(lcd, HD_DISPCTRL);
0338     return 0;
0339 }
0340
0341 static int charlcd_resume(struct device *dev)
0342 {
0343     struct charlcd *lcd = dev_get_drvdata(dev);
0344
0345     /* Turn the display back on */
0346     charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
0347     return 0;
0348 }
0349
0350 static const struct dev_pm_ops charlcd_pm_ops = {
0351     .suspend = charlcd_suspend,
0352     .resume = charlcd_resume,
0353 };
0354
0355 static const struct of_device_id charlcd_match[] = {
0356     { .compatible = "arm,versatile-lcd", },
0357     {}
0358 };
0359
0360 static struct platform_driver charlcd_driver = {
0361     .driver = {
0362         .name = DRIVERNAME,
0363         .pm = &charlcd_pm_ops,
0364         .suppress_bind_attrs = true,
0365         .of_match_table = of_match_ptr(charlcd_match),
0366     },
0367 };
0368 builtin_platform_driver_probe(charlcd_driver, charlcd_probe);