diff options
Diffstat (limited to 'drivers/auxdisplay/arm-charlcd.c')
| -rw-r--r-- | drivers/auxdisplay/arm-charlcd.c | 327 |
1 files changed, 327 insertions, 0 deletions
diff --git a/drivers/auxdisplay/arm-charlcd.c b/drivers/auxdisplay/arm-charlcd.c new file mode 100644 index 000000000..70efda4f7 --- /dev/null +++ b/drivers/auxdisplay/arm-charlcd.c @@ -0,0 +1,327 @@ +// 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 + * https://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/completion.h> +#include <linux/container_of.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/init.h> +#include <linux/interrupt.h> +#include <linux/iopoll.h> +#include <linux/platform_device.h> +#include <linux/string.h> +#include <linux/types.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 + * @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; + 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; + + /* If we can, use an IRQ to wait for the data, else poll */ + if (lcd->irq >= 0) + charlcd_wait_complete_irq(lcd); + else { + udelay(100); + readl_poll_timeout_atomic(lcd->virtbase + CHAR_RAW, val, + val & CHAR_RAW_VALID, 100, 1000); + 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 + */ + udelay(100); + readl_poll_timeout_atomic(lcd->virtbase + CHAR_RAW, val, + val & CHAR_RAW_VALID, 100, 1000); + 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; +} + +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) +{ + struct device *dev = &pdev->dev; + int ret; + struct charlcd *lcd; + + lcd = devm_kzalloc(dev, sizeof(*lcd), GFP_KERNEL); + if (!lcd) + return -ENOMEM; + + lcd->dev = &pdev->dev; + + lcd->virtbase = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(lcd->virtbase)) + return PTR_ERR(lcd->virtbase); + + lcd->irq = platform_get_irq(pdev, 0); + /* If no IRQ is supplied, we'll survive without it */ + if (lcd->irq >= 0) { + ret = devm_request_irq(dev, lcd->irq, charlcd_interrupt, 0, DRIVERNAME, lcd); + if (ret) + return ret; + } + + 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); + + return 0; +} + +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 = charlcd_match, + }, +}; +builtin_platform_driver_probe(charlcd_driver, charlcd_probe); |