// SPDX-License-Identifier: GPL-2.0 /* * Driver for the on-board character LCD found on some ARM reference boards * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it * http://en.wikipedia.org/wiki/HD44780_Character_LCD * Currently it will just display the text "ARM Linux" and the linux version * * Author: Linus Walleij <triad@df.lth.se> */ #include <linux/init.h> #include <linux/interrupt.h> #include <linux/platform_device.h> #include <linux/of.h> #include <linux/completion.h> #include <linux/delay.h> #include <linux/io.h> #include <linux/slab.h> #include <linux/workqueue.h> #include <generated/utsrelease.h> #define DRIVERNAME "arm-charlcd" #define CHARLCD_TIMEOUT (msecs_to_jiffies(1000)) /* Offsets to registers */ #define CHAR_COM 0x00U #define CHAR_DAT 0x04U #define CHAR_RD 0x08U #define CHAR_RAW 0x0CU #define CHAR_MASK 0x10U #define CHAR_STAT 0x14U #define CHAR_RAW_CLEAR 0x00000000U #define CHAR_RAW_VALID 0x00000100U /* Hitachi HD44780 display commands */ #define HD_CLEAR 0x01U #define HD_HOME 0x02U #define HD_ENTRYMODE 0x04U #define HD_ENTRYMODE_INCREMENT 0x02U #define HD_ENTRYMODE_SHIFT 0x01U #define HD_DISPCTRL 0x08U #define HD_DISPCTRL_ON 0x04U #define HD_DISPCTRL_CURSOR_ON 0x02U #define HD_DISPCTRL_CURSOR_BLINK 0x01U #define HD_CRSR_SHIFT 0x10U #define HD_CRSR_SHIFT_DISPLAY 0x08U #define HD_CRSR_SHIFT_DISPLAY_RIGHT 0x04U #define HD_FUNCSET 0x20U #define HD_FUNCSET_8BIT 0x10U #define HD_FUNCSET_2_LINES 0x08U #define HD_FUNCSET_FONT_5X10 0x04U #define HD_SET_CGRAM 0x40U #define HD_SET_DDRAM 0x80U #define HD_BUSY_FLAG 0x80U /** * struct charlcd - Private data structure * @dev: a pointer back to containing device * @phybase: the offset to the controller in physical memory * @physize: the size of the physical page * @virtbase: the offset to the controller in virtual memory * @irq: reserved interrupt number * @complete: completion structure for the last LCD command * @init_work: delayed work structure to initialize the display on boot */ struct charlcd { struct device *dev; u32 phybase; u32 physize; void __iomem *virtbase; int irq; struct completion complete; struct delayed_work init_work; }; static irqreturn_t charlcd_interrupt(int irq, void *data) { struct charlcd *lcd = data; u8 status; status = readl(lcd->virtbase + CHAR_STAT) & 0x01; /* Clear IRQ */ writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); if (status) complete(&lcd->complete); else dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status); return IRQ_HANDLED; } static void charlcd_wait_complete_irq(struct charlcd *lcd) { int ret; ret = wait_for_completion_interruptible_timeout(&lcd->complete, CHARLCD_TIMEOUT); /* Disable IRQ after completion */ writel(0x00, lcd->virtbase + CHAR_MASK); if (ret < 0) { dev_err(lcd->dev, "wait_for_completion_interruptible_timeout() " "returned %d waiting for ready\n", ret); return; } if (ret == 0) { dev_err(lcd->dev, "charlcd controller timed out " "waiting for ready\n"); return; } } static u8 charlcd_4bit_read_char(struct charlcd *lcd) { u8 data; u32 val; int i; /* If we can, use an IRQ to wait for the data, else poll */ if (lcd->irq >= 0) charlcd_wait_complete_irq(lcd); else { i = 0; val = 0; while (!(val & CHAR_RAW_VALID) && i < 10) { udelay(100); val = readl(lcd->virtbase + CHAR_RAW); i++; } writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); } msleep(1); /* Read the 4 high bits of the data */ data = readl(lcd->virtbase + CHAR_RD) & 0xf0; /* * The second read for the low bits does not trigger an IRQ * so in this case we have to poll for the 4 lower bits */ i = 0; val = 0; while (!(val & CHAR_RAW_VALID) && i < 10) { udelay(100); val = readl(lcd->virtbase + CHAR_RAW); i++; } writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); msleep(1); /* Read the 4 low bits of the data */ data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f; return data; } static bool charlcd_4bit_read_bf(struct charlcd *lcd) { if (lcd->irq >= 0) { /* * If we'll use IRQs to wait for the busyflag, clear any * pending flag and enable IRQ */ writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); init_completion(&lcd->complete); writel(0x01, lcd->virtbase + CHAR_MASK); } readl(lcd->virtbase + CHAR_COM); return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false; } static void charlcd_4bit_wait_busy(struct charlcd *lcd) { int retries = 50; udelay(100); while (charlcd_4bit_read_bf(lcd) && retries) retries--; if (!retries) dev_err(lcd->dev, "timeout waiting for busyflag\n"); } static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd) { u32 cmdlo = (cmd << 4) & 0xf0; u32 cmdhi = (cmd & 0xf0); writel(cmdhi, lcd->virtbase + CHAR_COM); udelay(10); writel(cmdlo, lcd->virtbase + CHAR_COM); charlcd_4bit_wait_busy(lcd); } static void charlcd_4bit_char(struct charlcd *lcd, u8 ch) { u32 chlo = (ch << 4) & 0xf0; u32 chhi = (ch & 0xf0); writel(chhi, lcd->virtbase + CHAR_DAT); udelay(10); writel(chlo, lcd->virtbase + CHAR_DAT); charlcd_4bit_wait_busy(lcd); } static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str) { u8 offset; int i; /* * We support line 0, 1 * Line 1 runs from 0x00..0x27 * Line 2 runs from 0x28..0x4f */ if (line == 0) offset = 0; else if (line == 1) offset = 0x28; else return; /* Set offset */ charlcd_4bit_command(lcd, HD_SET_DDRAM | offset); /* Send string */ for (i = 0; i < strlen(str) && i < 0x28; i++) charlcd_4bit_char(lcd, str[i]); } static void charlcd_4bit_init(struct charlcd *lcd) { /* These commands cannot be checked with the busy flag */ writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); msleep(5); writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); udelay(100); writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); udelay(100); /* Go to 4bit mode */ writel(HD_FUNCSET, lcd->virtbase + CHAR_COM); udelay(100); /* * 4bit mode, 2 lines, 5x8 font, after this the number of lines * and the font cannot be changed until the next initialization sequence */ charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES); charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON); charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT); charlcd_4bit_command(lcd, HD_CLEAR); charlcd_4bit_command(lcd, HD_HOME); /* Put something useful in the display */ charlcd_4bit_print(lcd, 0, "ARM Linux"); charlcd_4bit_print(lcd, 1, UTS_RELEASE); } static void charlcd_init_work(struct work_struct *work) { struct charlcd *lcd = container_of(work, struct charlcd, init_work.work); charlcd_4bit_init(lcd); } static int __init charlcd_probe(struct platform_device *pdev) { int ret; struct charlcd *lcd; struct resource *res; lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL); if (!lcd) return -ENOMEM; lcd->dev = &pdev->dev; res = platform_get_resource(pdev, IORESOURCE_MEM, 0); if (!res) { ret = -ENOENT; goto out_no_resource; } lcd->phybase = res->start; lcd->physize = resource_size(res); if (request_mem_region(lcd->phybase, lcd->physize, DRIVERNAME) == NULL) { ret = -EBUSY; goto out_no_memregion; } lcd->virtbase = ioremap(lcd->phybase, lcd->physize); if (!lcd->virtbase) { ret = -ENOMEM; goto out_no_memregion; } lcd->irq = platform_get_irq(pdev, 0); /* If no IRQ is supplied, we'll survive without it */ if (lcd->irq >= 0) { if (request_irq(lcd->irq, charlcd_interrupt, 0, DRIVERNAME, lcd)) { ret = -EIO; goto out_no_irq; } } platform_set_drvdata(pdev, lcd); /* * Initialize the display in a delayed work, because * it is VERY slow and would slow down the boot of the system. */ INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work); schedule_delayed_work(&lcd->init_work, 0); dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n", lcd->phybase); return 0; out_no_irq: iounmap(lcd->virtbase); out_no_memregion: release_mem_region(lcd->phybase, SZ_4K); out_no_resource: kfree(lcd); return ret; } static int charlcd_suspend(struct device *dev) { struct charlcd *lcd = dev_get_drvdata(dev); /* Power the display off */ charlcd_4bit_command(lcd, HD_DISPCTRL); return 0; } static int charlcd_resume(struct device *dev) { struct charlcd *lcd = dev_get_drvdata(dev); /* Turn the display back on */ charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON); return 0; } static const struct dev_pm_ops charlcd_pm_ops = { .suspend = charlcd_suspend, .resume = charlcd_resume, }; static const struct of_device_id charlcd_match[] = { { .compatible = "arm,versatile-lcd", }, {} }; static struct platform_driver charlcd_driver = { .driver = { .name = DRIVERNAME, .pm = &charlcd_pm_ops, .suppress_bind_attrs = true, .of_match_table = of_match_ptr(charlcd_match), }, }; builtin_platform_driver_probe(charlcd_driver, charlcd_probe);