// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * QNAP Turbo NAS Board power off. Can also be used on Synology devices.
 *
 * Copyright (C) 2012 Andrew Lunn <andrew@lunn.ch>
 *
 * Based on the code from:
 *
 * Copyright (C) 2009  Martin Michlmayr <tbm@cyrius.com>
 * Copyright (C) 2008  Byron Bradley <byron.bbradley@gmail.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/serial_reg.h>
#include <linux/of.h>
#include <linux/io.h>
#include <linux/clk.h>

#define UART1_REG(x)    (base + ((UART_##x) << 2))

struct power_off_cfg {
        u32 baud;
        char cmd;
};

static const struct power_off_cfg qnap_power_off_cfg = {
        .baud = 19200,
        .cmd = 'A',
};

static const struct power_off_cfg synology_power_off_cfg = {
        .baud = 9600,
        .cmd = '1',
};

static const struct of_device_id qnap_power_off_of_match_table[] = {
        { .compatible = "qnap,power-off",
          .data = &qnap_power_off_cfg,
        },
        { .compatible = "synology,power-off",
          .data = &synology_power_off_cfg,
        },
        {}
};
MODULE_DEVICE_TABLE(of, qnap_power_off_of_match_table);

static void __iomem *base;
static unsigned long tclk;
static const struct power_off_cfg *cfg;

static void qnap_power_off(void)
{
        const unsigned divisor = ((tclk + (8 * cfg->baud)) / (16 * cfg->baud));

        pr_err("%s: triggering power-off...\n", __func__);

        /* hijack UART1 and reset into sane state */
        writel(0x83, UART1_REG(LCR));
        writel(divisor & 0xff, UART1_REG(DLL));
        writel((divisor >> 8) & 0xff, UART1_REG(DLM));
        writel(0x03, UART1_REG(LCR));
        writel(0x00, UART1_REG(IER));
        writel(0x00, UART1_REG(FCR));
        writel(0x00, UART1_REG(MCR));

        /* send the power-off command to PIC */
        writel(cfg->cmd, UART1_REG(TX));
}

static int qnap_power_off_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct resource *res;
        struct clk *clk;

        const struct of_device_id *match =
                of_match_node(qnap_power_off_of_match_table, np);
        cfg = match->data;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res) {
                dev_err(&pdev->dev, "Missing resource");
                return -EINVAL;
        }

        base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
        if (!base) {
                dev_err(&pdev->dev, "Unable to map resource");
                return -EINVAL;
        }

        /* We need to know tclk in order to calculate the UART divisor */
        clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(clk)) {
                dev_err(&pdev->dev, "Clk missing");
                return PTR_ERR(clk);
        }

        tclk = clk_get_rate(clk);

        /* Check that nothing else has already setup a handler */
        if (pm_power_off) {
                dev_err(&pdev->dev, "pm_power_off already claimed for %ps",
                        pm_power_off);
                return -EBUSY;
        }
        pm_power_off = qnap_power_off;

        return 0;
}

static void qnap_power_off_remove(struct platform_device *pdev)
{
        pm_power_off = NULL;
}

static struct platform_driver qnap_power_off_driver = {
        .probe  = qnap_power_off_probe,
        .remove = qnap_power_off_remove,
        .driver = {
                .name   = "qnap_power_off",
                .of_match_table = of_match_ptr(qnap_power_off_of_match_table),
        },
};
module_platform_driver(qnap_power_off_driver);

MODULE_AUTHOR("Andrew Lunn <andrew@lunn.ch>");
MODULE_DESCRIPTION("QNAP Power off driver");
MODULE_LICENSE("GPL v2");