// SPDX-License-Identifier: GPL-2.0-only
/*
 * A64FX diag driver.
 * Copyright (c) 2022 Fujitsu Ltd.
 */

#include <linux/acpi.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/platform_device.h>

#define A64FX_DIAG_IRQ 1
#define BMC_DIAG_INTERRUPT_ENABLE 0x40
#define BMC_DIAG_INTERRUPT_STATUS 0x44
#define BMC_DIAG_INTERRUPT_MASK BIT(31)

struct a64fx_diag_priv {
        void __iomem *mmsc_reg_base;
        int irq;
        bool has_nmi;
};

static irqreturn_t a64fx_diag_handler_nmi(int irq, void *dev_id)
{
        nmi_panic(NULL, "a64fx_diag: interrupt received\n");

        return IRQ_HANDLED;
}

static irqreturn_t a64fx_diag_handler_irq(int irq, void *dev_id)
{
        panic("a64fx_diag: interrupt received\n");

        return IRQ_HANDLED;
}

static void a64fx_diag_interrupt_clear(struct a64fx_diag_priv *priv)
{
        void __iomem *diag_status_reg_addr;
        u32 mmsc;

        diag_status_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_STATUS;
        mmsc = readl(diag_status_reg_addr);
        if (mmsc & BMC_DIAG_INTERRUPT_MASK)
                writel(BMC_DIAG_INTERRUPT_MASK, diag_status_reg_addr);
}

static void a64fx_diag_interrupt_enable(struct a64fx_diag_priv *priv)
{
        void __iomem *diag_enable_reg_addr;
        u32 mmsc;

        diag_enable_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_ENABLE;
        mmsc = readl(diag_enable_reg_addr);
        if (!(mmsc & BMC_DIAG_INTERRUPT_MASK)) {
                mmsc |= BMC_DIAG_INTERRUPT_MASK;
                writel(mmsc, diag_enable_reg_addr);
        }
}

static void a64fx_diag_interrupt_disable(struct a64fx_diag_priv *priv)
{
        void __iomem *diag_enable_reg_addr;
        u32 mmsc;

        diag_enable_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_ENABLE;
        mmsc = readl(diag_enable_reg_addr);
        if (mmsc & BMC_DIAG_INTERRUPT_MASK) {
                mmsc &= ~BMC_DIAG_INTERRUPT_MASK;
                writel(mmsc, diag_enable_reg_addr);
        }
}

static int a64fx_diag_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct a64fx_diag_priv *priv;
        unsigned long irq_flags;
        int ret;

        priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
        if (priv == NULL)
                return -ENOMEM;

        priv->mmsc_reg_base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(priv->mmsc_reg_base))
                return PTR_ERR(priv->mmsc_reg_base);

        priv->irq = platform_get_irq(pdev, A64FX_DIAG_IRQ);
        if (priv->irq < 0)
                return priv->irq;

        platform_set_drvdata(pdev, priv);

        irq_flags = IRQF_PERCPU | IRQF_NOBALANCING | IRQF_NO_AUTOEN |
                   IRQF_NO_THREAD;
        ret = request_nmi(priv->irq, &a64fx_diag_handler_nmi, irq_flags,
                        "a64fx_diag_nmi", NULL);
        if (ret) {
                ret = request_irq(priv->irq, &a64fx_diag_handler_irq,
                                irq_flags, "a64fx_diag_irq", NULL);
                if (ret) {
                        dev_err(dev, "cannot register IRQ %d\n", ret);
                        return ret;
                }
                enable_irq(priv->irq);
        } else {
                enable_nmi(priv->irq);
                priv->has_nmi = true;
        }

        a64fx_diag_interrupt_clear(priv);
        a64fx_diag_interrupt_enable(priv);

        return 0;
}

static void a64fx_diag_remove(struct platform_device *pdev)
{
        struct a64fx_diag_priv *priv = platform_get_drvdata(pdev);

        a64fx_diag_interrupt_disable(priv);
        a64fx_diag_interrupt_clear(priv);

        if (priv->has_nmi)
                free_nmi(priv->irq, NULL);
        else
                free_irq(priv->irq, NULL);
}

static const struct acpi_device_id a64fx_diag_acpi_match[] = {
        { "FUJI2007", 0 },
        { },
};
MODULE_DEVICE_TABLE(acpi, a64fx_diag_acpi_match);


static struct platform_driver a64fx_diag_driver = {
        .driver = {
                .name = "a64fx_diag_driver",
                .acpi_match_table = ACPI_PTR(a64fx_diag_acpi_match),
        },
        .probe = a64fx_diag_probe,
        .remove = a64fx_diag_remove,
};

module_platform_driver(a64fx_diag_driver);

MODULE_AUTHOR("Hitomi Hasegawa <hasegawa-hitomi@fujitsu.com>");
MODULE_DESCRIPTION("A64FX diag driver");