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1// SPDX-License-Identifier: GPL-2.02/*3 * Driver for the on-board character LCD found on some ARM reference boards4 * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it5 * https://en.wikipedia.org/wiki/HD44780_Character_LCD6 * Currently it will just display the text "ARM Linux" and the linux version7 *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 0x00U26#define CHAR_DAT 0x04U27#define CHAR_RD 0x08U28#define CHAR_RAW 0x0CU29#define CHAR_MASK 0x10U30#define CHAR_STAT 0x14U31 32#define CHAR_RAW_CLEAR 0x00000000U33#define CHAR_RAW_VALID 0x00000100U34 35/* Hitachi HD44780 display commands */36#define HD_CLEAR 0x01U37#define HD_HOME 0x02U38#define HD_ENTRYMODE 0x04U39#define HD_ENTRYMODE_INCREMENT 0x02U40#define HD_ENTRYMODE_SHIFT 0x01U41#define HD_DISPCTRL 0x08U42#define HD_DISPCTRL_ON 0x04U43#define HD_DISPCTRL_CURSOR_ON 0x02U44#define HD_DISPCTRL_CURSOR_BLINK 0x01U45#define HD_CRSR_SHIFT 0x10U46#define HD_CRSR_SHIFT_DISPLAY 0x08U47#define HD_CRSR_SHIFT_DISPLAY_RIGHT 0x04U48#define HD_FUNCSET 0x20U49#define HD_FUNCSET_8BIT 0x10U50#define HD_FUNCSET_2_LINES 0x08U51#define HD_FUNCSET_FONT_5X10 0x04U52#define HD_SET_CGRAM 0x40U53#define HD_SET_DDRAM 0x80U54#define HD_BUSY_FLAG 0x80U55 56/**57 * struct charlcd - Private data structure58 * @dev: a pointer back to containing device59 * @phybase: the offset to the controller in physical memory60 * @physize: the size of the physical page61 * @virtbase: the offset to the controller in virtual memory62 * @irq: reserved interrupt number63 * @complete: completion structure for the last LCD command64 * @init_work: delayed work structure to initialize the display on boot65 */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 else87 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 IRQ142 * so in this case we have to poll for the 4 lower bits143 */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 any165 * pending flag and enable IRQ166 */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, 1215 * Line 1 runs from 0x00..0x27216 * Line 2 runs from 0x28..0x4f217 */218 if (line == 0)219 offset = 0;220 else if (line == 1)221 offset = 0x28;222 else223 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 lines247 * and the font cannot be changed until the next initialization sequence248 */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(*lcd), 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, because313 * 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