// 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/mod_devicetable.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);