// SPDX-License-Identifier: GPL-2.0+
/*
 * Surface Book (2 and later) hot-plug driver.
 *
 * Surface Book devices (can) have a hot-pluggable discrete GPU (dGPU). This
 * driver is responsible for out-of-band hot-plug event signaling on these
 * devices. It is specifically required when the hot-plug device is in D3cold
 * and can thus not generate PCIe hot-plug events itself.
 *
 * Event signaling is handled via ACPI, which will generate the appropriate
 * device-check notifications to be picked up by the PCIe hot-plug driver.
 *
 * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
 */

#include <linux/acpi.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>

static const struct acpi_gpio_params shps_base_presence_int   = { 0, 0, false };
static const struct acpi_gpio_params shps_base_presence       = { 1, 0, false };
static const struct acpi_gpio_params shps_device_power_int    = { 2, 0, false };
static const struct acpi_gpio_params shps_device_power        = { 3, 0, false };
static const struct acpi_gpio_params shps_device_presence_int = { 4, 0, false };
static const struct acpi_gpio_params shps_device_presence     = { 5, 0, false };

static const struct acpi_gpio_mapping shps_acpi_gpios[] = {
        { "base_presence-int-gpio",   &shps_base_presence_int,   1 },
        { "base_presence-gpio",       &shps_base_presence,       1 },
        { "device_power-int-gpio",    &shps_device_power_int,    1 },
        { "device_power-gpio",        &shps_device_power,        1 },
        { "device_presence-int-gpio", &shps_device_presence_int, 1 },
        { "device_presence-gpio",     &shps_device_presence,     1 },
        { },
};

/* 5515a847-ed55-4b27-8352-cd320e10360a */
static const guid_t shps_dsm_guid =
        GUID_INIT(0x5515a847, 0xed55, 0x4b27, 0x83, 0x52, 0xcd, 0x32, 0x0e, 0x10, 0x36, 0x0a);

#define SHPS_DSM_REVISION               1

enum shps_dsm_fn {
        SHPS_DSM_FN_PCI_NUM_ENTRIES     = 0x01,
        SHPS_DSM_FN_PCI_GET_ENTRIES     = 0x02,
        SHPS_DSM_FN_IRQ_BASE_PRESENCE   = 0x03,
        SHPS_DSM_FN_IRQ_DEVICE_POWER    = 0x04,
        SHPS_DSM_FN_IRQ_DEVICE_PRESENCE = 0x05,
};

enum shps_irq_type {
        /* NOTE: Must be in order of enum shps_dsm_fn above. */
        SHPS_IRQ_TYPE_BASE_PRESENCE     = 0,
        SHPS_IRQ_TYPE_DEVICE_POWER      = 1,
        SHPS_IRQ_TYPE_DEVICE_PRESENCE   = 2,
        SHPS_NUM_IRQS,
};

static const char *const shps_gpio_names[] = {
        [SHPS_IRQ_TYPE_BASE_PRESENCE]   = "base_presence",
        [SHPS_IRQ_TYPE_DEVICE_POWER]    = "device_power",
        [SHPS_IRQ_TYPE_DEVICE_PRESENCE] = "device_presence",
};

struct shps_device {
        struct mutex lock[SHPS_NUM_IRQS];  /* Protects update in shps_dsm_notify_irq() */
        struct gpio_desc *gpio[SHPS_NUM_IRQS];
        unsigned int irq[SHPS_NUM_IRQS];
};

#define SHPS_IRQ_NOT_PRESENT            ((unsigned int)-1)

static enum shps_dsm_fn shps_dsm_fn_for_irq(enum shps_irq_type type)
{
        return SHPS_DSM_FN_IRQ_BASE_PRESENCE + type;
}

static void shps_dsm_notify_irq(struct platform_device *pdev, enum shps_irq_type type)
{
        struct shps_device *sdev = platform_get_drvdata(pdev);
        acpi_handle handle = ACPI_HANDLE(&pdev->dev);
        union acpi_object *result;
        union acpi_object param;
        int value;

        mutex_lock(&sdev->lock[type]);

        value = gpiod_get_value_cansleep(sdev->gpio[type]);
        if (value < 0) {
                mutex_unlock(&sdev->lock[type]);
                dev_err(&pdev->dev, "failed to get gpio: %d (irq=%d)\n", type, value);
                return;
        }

        dev_dbg(&pdev->dev, "IRQ notification via DSM (irq=%d, value=%d)\n", type, value);

        param.type = ACPI_TYPE_INTEGER;
        param.integer.value = value;

        result = acpi_evaluate_dsm_typed(handle, &shps_dsm_guid, SHPS_DSM_REVISION,
                                         shps_dsm_fn_for_irq(type), &param, ACPI_TYPE_BUFFER);
        if (!result) {
                dev_err(&pdev->dev, "IRQ notification via DSM failed (irq=%d, gpio=%d)\n",
                        type, value);

        } else if (result->buffer.length != 1 || result->buffer.pointer[0] != 0) {
                dev_err(&pdev->dev,
                        "IRQ notification via DSM failed: unexpected result value (irq=%d, gpio=%d)\n",
                        type, value);
        }

        mutex_unlock(&sdev->lock[type]);

        ACPI_FREE(result);
}

static irqreturn_t shps_handle_irq(int irq, void *data)
{
        struct platform_device *pdev = data;
        struct shps_device *sdev = platform_get_drvdata(pdev);
        int type;

        /* Figure out which IRQ we're handling. */
        for (type = 0; type < SHPS_NUM_IRQS; type++)
                if (irq == sdev->irq[type])
                        break;

        /* We should have found our interrupt, if not: this is a bug. */
        if (WARN(type >= SHPS_NUM_IRQS, "invalid IRQ number: %d\n", irq))
                return IRQ_HANDLED;

        /* Forward interrupt to ACPI via DSM. */
        shps_dsm_notify_irq(pdev, type);
        return IRQ_HANDLED;
}

static int shps_setup_irq(struct platform_device *pdev, enum shps_irq_type type)
{
        unsigned long flags = IRQF_ONESHOT | IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING;
        struct shps_device *sdev = platform_get_drvdata(pdev);
        struct gpio_desc *gpiod;
        acpi_handle handle = ACPI_HANDLE(&pdev->dev);
        const char *irq_name;
        const int dsm = shps_dsm_fn_for_irq(type);
        int status, irq;

        /*
         * Only set up interrupts that we actually need: The Surface Book 3
         * does not have a DSM for base presence, so don't set up an interrupt
         * for that.
         */
        if (!acpi_check_dsm(handle, &shps_dsm_guid, SHPS_DSM_REVISION, BIT(dsm))) {
                dev_dbg(&pdev->dev, "IRQ notification via DSM not present (irq=%d)\n", type);
                return 0;
        }

        gpiod = devm_gpiod_get(&pdev->dev, shps_gpio_names[type], GPIOD_ASIS);
        if (IS_ERR(gpiod))
                return PTR_ERR(gpiod);

        irq = gpiod_to_irq(gpiod);
        if (irq < 0)
                return irq;

        irq_name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "shps-irq-%d", type);
        if (!irq_name)
                return -ENOMEM;

        status = devm_request_threaded_irq(&pdev->dev, irq, NULL, shps_handle_irq,
                                           flags, irq_name, pdev);
        if (status)
                return status;

        dev_dbg(&pdev->dev, "set up irq %d as type %d\n", irq, type);

        sdev->gpio[type] = gpiod;
        sdev->irq[type] = irq;

        return 0;
}

static void surface_hotplug_remove(struct platform_device *pdev)
{
        struct shps_device *sdev = platform_get_drvdata(pdev);
        int i;

        /* Ensure that IRQs have been fully handled and won't trigger any more. */
        for (i = 0; i < SHPS_NUM_IRQS; i++) {
                if (sdev->irq[i] != SHPS_IRQ_NOT_PRESENT)
                        disable_irq(sdev->irq[i]);

                mutex_destroy(&sdev->lock[i]);
        }
}

static int surface_hotplug_probe(struct platform_device *pdev)
{
        struct shps_device *sdev;
        int status, i;

        /*
         * The MSHW0153 device is also present on the Surface Laptop 3,
         * however that doesn't have a hot-pluggable PCIe device. It also
         * doesn't have any GPIO interrupts/pins under the MSHW0153, so filter
         * it out here.
         */
        if (gpiod_count(&pdev->dev, NULL) < 0)
                return -ENODEV;

        status = devm_acpi_dev_add_driver_gpios(&pdev->dev, shps_acpi_gpios);
        if (status)
                return status;

        sdev = devm_kzalloc(&pdev->dev, sizeof(*sdev), GFP_KERNEL);
        if (!sdev)
                return -ENOMEM;

        platform_set_drvdata(pdev, sdev);

        /*
         * Initialize IRQs so that we can safely call surface_hotplug_remove()
         * on errors.
         */
        for (i = 0; i < SHPS_NUM_IRQS; i++)
                sdev->irq[i] = SHPS_IRQ_NOT_PRESENT;

        /* Set up IRQs. */
        for (i = 0; i < SHPS_NUM_IRQS; i++) {
                mutex_init(&sdev->lock[i]);

                status = shps_setup_irq(pdev, i);
                if (status) {
                        dev_err(&pdev->dev, "failed to set up IRQ %d: %d\n", i, status);
                        goto err;
                }
        }

        /* Ensure everything is up-to-date. */
        for (i = 0; i < SHPS_NUM_IRQS; i++)
                if (sdev->irq[i] != SHPS_IRQ_NOT_PRESENT)
                        shps_dsm_notify_irq(pdev, i);

        return 0;

err:
        surface_hotplug_remove(pdev);
        return status;
}

static const struct acpi_device_id surface_hotplug_acpi_match[] = {
        { "MSHW0153", 0 },
        { },
};
MODULE_DEVICE_TABLE(acpi, surface_hotplug_acpi_match);

static struct platform_driver surface_hotplug_driver = {
        .probe = surface_hotplug_probe,
        .remove = surface_hotplug_remove,
        .driver = {
                .name = "surface_hotplug",
                .acpi_match_table = surface_hotplug_acpi_match,
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        },
};
module_platform_driver(surface_hotplug_driver);

MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
MODULE_DESCRIPTION("Surface Hot-Plug Signaling Driver for Surface Book Devices");
MODULE_LICENSE("GPL");