Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

[drm/drm-misc.git] / drivers / platform / surface / aggregator / core.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Surface Serial Hub (SSH) driver for communication with the Surface/System
 * Aggregator Module (SSAM/SAM).
 *
 * Provides access to a SAM-over-SSH connected EC via a controller device.
 * Handles communication via requests as well as enabling, disabling, and
 * relaying of events.
 *
 * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
 */

#include <linux/acpi.h>
#include <linux/atomic.h>
#include <linux/completion.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/serdev.h>
#include <linux/sysfs.h>
#include <linux/units.h>

#include <linux/surface_aggregator/controller.h>
#include <linux/surface_aggregator/device.h>

#include "bus.h"
#include "controller.h"

#define CREATE_TRACE_POINTS
#include "trace.h"


/* -- Static controller reference. ------------------------------------------ */

/*
 * Main controller reference. The corresponding lock must be held while
 * accessing (reading/writing) the reference.
 */
static struct ssam_controller *__ssam_controller;
static DEFINE_SPINLOCK(__ssam_controller_lock);

/**
 * ssam_get_controller() - Get reference to SSAM controller.
 *
 * Returns a reference to the SSAM controller of the system or %NULL if there
 * is none, it hasn't been set up yet, or it has already been unregistered.
 * This function automatically increments the reference count of the
 * controller, thus the calling party must ensure that ssam_controller_put()
 * is called when it doesn't need the controller any more.
 */
struct ssam_controller *ssam_get_controller(void)
{
        struct ssam_controller *ctrl;

        spin_lock(&__ssam_controller_lock);

        ctrl = __ssam_controller;
        if (!ctrl)
                goto out;

        if (WARN_ON(!kref_get_unless_zero(&ctrl->kref)))
                ctrl = NULL;

out:
        spin_unlock(&__ssam_controller_lock);
        return ctrl;
}
EXPORT_SYMBOL_GPL(ssam_get_controller);

/**
 * ssam_try_set_controller() - Try to set the main controller reference.
 * @ctrl: The controller to which the reference should point.
 *
 * Set the main controller reference to the given pointer if the reference
 * hasn't been set already.
 *
 * Return: Returns zero on success or %-EEXIST if the reference has already
 * been set.
 */
static int ssam_try_set_controller(struct ssam_controller *ctrl)
{
        int status = 0;

        spin_lock(&__ssam_controller_lock);
        if (!__ssam_controller)
                __ssam_controller = ctrl;
        else
                status = -EEXIST;
        spin_unlock(&__ssam_controller_lock);

        return status;
}

/**
 * ssam_clear_controller() - Remove/clear the main controller reference.
 *
 * Clears the main controller reference, i.e. sets it to %NULL. This function
 * should be called before the controller is shut down.
 */
static void ssam_clear_controller(void)
{
        spin_lock(&__ssam_controller_lock);
        __ssam_controller = NULL;
        spin_unlock(&__ssam_controller_lock);
}

/**
 * ssam_client_link() - Link an arbitrary client device to the controller.
 * @c: The controller to link to.
 * @client: The client device.
 *
 * Link an arbitrary client device to the controller by creating a device link
 * between it as consumer and the controller device as provider. This function
 * can be used for non-SSAM devices (or SSAM devices not registered as child
 * under the controller) to guarantee that the controller is valid for as long
 * as the driver of the client device is bound, and that proper suspend and
 * resume ordering is guaranteed.
 *
 * The device link does not have to be destructed manually. It is removed
 * automatically once the driver of the client device unbinds.
 *
 * Return: Returns zero on success, %-ENODEV if the controller is not ready or
 * going to be removed soon, or %-ENOMEM if the device link could not be
 * created for other reasons.
 */
int ssam_client_link(struct ssam_controller *c, struct device *client)
{
        const u32 flags = DL_FLAG_PM_RUNTIME | DL_FLAG_AUTOREMOVE_CONSUMER;
        struct device_link *link;
        struct device *ctrldev;

        ssam_controller_statelock(c);

        if (c->state != SSAM_CONTROLLER_STARTED) {
                ssam_controller_stateunlock(c);
                return -ENODEV;
        }

        ctrldev = ssam_controller_device(c);
        if (!ctrldev) {
                ssam_controller_stateunlock(c);
                return -ENODEV;
        }

        link = device_link_add(client, ctrldev, flags);
        if (!link) {
                ssam_controller_stateunlock(c);
                return -ENOMEM;
        }

        /*
         * Return -ENODEV if supplier driver is on its way to be removed. In
         * this case, the controller won't be around for much longer and the
         * device link is not going to save us any more, as unbinding is
         * already in progress.
         */
        if (READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND) {
                ssam_controller_stateunlock(c);
                return -ENODEV;
        }

        ssam_controller_stateunlock(c);
        return 0;
}
EXPORT_SYMBOL_GPL(ssam_client_link);

/**
 * ssam_client_bind() - Bind an arbitrary client device to the controller.
 * @client: The client device.
 *
 * Link an arbitrary client device to the controller by creating a device link
 * between it as consumer and the main controller device as provider. This
 * function can be used for non-SSAM devices to guarantee that the controller
 * returned by this function is valid for as long as the driver of the client
 * device is bound, and that proper suspend and resume ordering is guaranteed.
 *
 * This function does essentially the same as ssam_client_link(), except that
 * it first fetches the main controller reference, then creates the link, and
 * finally returns this reference. Note that this function does not increment
 * the reference counter of the controller, as, due to the link, the
 * controller lifetime is assured as long as the driver of the client device
 * is bound.
 *
 * It is not valid to use the controller reference obtained by this method
 * outside of the driver bound to the client device at the time of calling
 * this function, without first incrementing the reference count of the
 * controller via ssam_controller_get(). Even after doing this, care must be
 * taken that requests are only submitted and notifiers are only
 * (un-)registered when the controller is active and not suspended. In other
 * words: The device link only lives as long as the client driver is bound and
 * any guarantees enforced by this link (e.g. active controller state) can
 * only be relied upon as long as this link exists and may need to be enforced
 * in other ways afterwards.
 *
 * The created device link does not have to be destructed manually. It is
 * removed automatically once the driver of the client device unbinds.
 *
 * Return: Returns the controller on success, an error pointer with %-ENODEV
 * if the controller is not present, not ready or going to be removed soon, or
 * %-ENOMEM if the device link could not be created for other reasons.
 */
struct ssam_controller *ssam_client_bind(struct device *client)
{
        struct ssam_controller *c;
        int status;

        c = ssam_get_controller();
        if (!c)
                return ERR_PTR(-ENODEV);

        status = ssam_client_link(c, client);

        /*
         * Note that we can drop our controller reference in both success and
         * failure cases: On success, we have bound the controller lifetime
         * inherently to the client driver lifetime, i.e. it the controller is
         * now guaranteed to outlive the client driver. On failure, we're not
         * going to use the controller any more.
         */
        ssam_controller_put(c);

        return status >= 0 ? c : ERR_PTR(status);
}
EXPORT_SYMBOL_GPL(ssam_client_bind);


/* -- Glue layer (serdev_device -> ssam_controller). ------------------------ */

static size_t ssam_receive_buf(struct serdev_device *dev, const u8 *buf,
                               size_t n)
{
        struct ssam_controller *ctrl;
        int ret;

        ctrl = serdev_device_get_drvdata(dev);
        ret = ssam_controller_receive_buf(ctrl, buf, n);

        return ret < 0 ? 0 : ret;
}

static void ssam_write_wakeup(struct serdev_device *dev)
{
        ssam_controller_write_wakeup(serdev_device_get_drvdata(dev));
}

static const struct serdev_device_ops ssam_serdev_ops = {
        .receive_buf = ssam_receive_buf,
        .write_wakeup = ssam_write_wakeup,
};


/* -- SysFS and misc. ------------------------------------------------------- */

static int ssam_log_firmware_version(struct ssam_controller *ctrl)
{
        u32 version, a, b, c;
        int status;

        status = ssam_get_firmware_version(ctrl, &version);
        if (status)
                return status;

        a = (version >> 24) & 0xff;
        b = ((version >> 8) & 0xffff);
        c = version & 0xff;

        ssam_info(ctrl, "SAM firmware version: %u.%u.%u\n", a, b, c);
        return 0;
}

static ssize_t firmware_version_show(struct device *dev,
                                     struct device_attribute *attr, char *buf)
{
        struct ssam_controller *ctrl = dev_get_drvdata(dev);
        u32 version, a, b, c;
        int status;

        status = ssam_get_firmware_version(ctrl, &version);
        if (status < 0)
                return status;

        a = (version >> 24) & 0xff;
        b = ((version >> 8) & 0xffff);
        c = version & 0xff;

        return sysfs_emit(buf, "%u.%u.%u\n", a, b, c);
}
static DEVICE_ATTR_RO(firmware_version);

static struct attribute *ssam_sam_attrs[] = {
        &dev_attr_firmware_version.attr,
        NULL
};

static const struct attribute_group ssam_sam_group = {
        .name = "sam",
        .attrs = ssam_sam_attrs,
};


/* -- Serial device setup. -------------------------------------------------- */

static acpi_status ssam_serdev_setup_via_acpi_crs(struct acpi_resource *rsc,
                                                  void *ctx)
{
        struct serdev_device *serdev = ctx;
        struct acpi_resource_uart_serialbus *uart;
        bool flow_control;
        int status = 0;

        if (!serdev_acpi_get_uart_resource(rsc, &uart))
                return AE_OK;

        /* Set up serdev device. */
        serdev_device_set_baudrate(serdev, uart->default_baud_rate);

        /* serdev currently only supports RTSCTS flow control. */
        if (uart->flow_control & (~((u8)ACPI_UART_FLOW_CONTROL_HW))) {
                dev_warn(&serdev->dev, "setup: unsupported flow control (value: %#04x)\n",
                         uart->flow_control);
        }

        /* Set RTSCTS flow control. */
        flow_control = uart->flow_control & ACPI_UART_FLOW_CONTROL_HW;
        serdev_device_set_flow_control(serdev, flow_control);

        /* serdev currently only supports EVEN/ODD parity. */
        switch (uart->parity) {
        case ACPI_UART_PARITY_NONE:
                status = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
                break;
        case ACPI_UART_PARITY_EVEN:
                status = serdev_device_set_parity(serdev, SERDEV_PARITY_EVEN);
                break;
        case ACPI_UART_PARITY_ODD:
                status = serdev_device_set_parity(serdev, SERDEV_PARITY_ODD);
                break;
        default:
                dev_warn(&serdev->dev, "setup: unsupported parity (value: %#04x)\n",
                         uart->parity);
                break;
        }

        if (status) {
                dev_err(&serdev->dev, "setup: failed to set parity (value: %#04x, error: %d)\n",
                        uart->parity, status);
                return AE_ERROR;
        }

        /* We've found the resource and are done. */
        return AE_CTRL_TERMINATE;
}

static int ssam_serdev_setup_via_acpi(struct serdev_device *serdev, acpi_handle handle)
{
        acpi_status status;

        status = acpi_walk_resources(handle, METHOD_NAME__CRS,
                                     ssam_serdev_setup_via_acpi_crs, serdev);

        return status ? -ENXIO : 0;
}

static int ssam_serdev_setup(struct acpi_device *ssh, struct serdev_device *serdev)
{
        if (ssh)
                return ssam_serdev_setup_via_acpi(serdev, ssh->handle);

        /* TODO: these values may differ per board/implementation */
        serdev_device_set_baudrate(serdev, 4 * HZ_PER_MHZ);
        serdev_device_set_flow_control(serdev, true);
        serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);

        return 0;
}

/* -- Power management. ----------------------------------------------------- */

static void ssam_serial_hub_shutdown(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        /*
         * Try to disable notifiers, signal display-off and D0-exit, ignore any
         * errors.
         *
         * Note: It has not been established yet if this is actually
         * necessary/useful for shutdown.
         */

        status = ssam_notifier_disable_registered(c);
        if (status) {
                ssam_err(c, "pm: failed to disable notifiers for shutdown: %d\n",
                         status);
        }

        status = ssam_ctrl_notif_display_off(c);
        if (status)
                ssam_err(c, "pm: display-off notification failed: %d\n", status);

        status = ssam_ctrl_notif_d0_exit(c);
        if (status)
                ssam_err(c, "pm: D0-exit notification failed: %d\n", status);
}

#ifdef CONFIG_PM_SLEEP

static int ssam_serial_hub_pm_prepare(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        /*
         * Try to signal display-off, This will quiesce events.
         *
         * Note: Signaling display-off/display-on should normally be done from
         * some sort of display state notifier. As that is not available,
         * signal it here.
         */

        status = ssam_ctrl_notif_display_off(c);
        if (status)
                ssam_err(c, "pm: display-off notification failed: %d\n", status);

        return status;
}

static void ssam_serial_hub_pm_complete(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        /*
         * Try to signal display-on. This will restore events.
         *
         * Note: Signaling display-off/display-on should normally be done from
         * some sort of display state notifier. As that is not available,
         * signal it here.
         */

        status = ssam_ctrl_notif_display_on(c);
        if (status)
                ssam_err(c, "pm: display-on notification failed: %d\n", status);
}

static int ssam_serial_hub_pm_suspend(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        /*
         * Try to signal D0-exit, enable IRQ wakeup if specified. Abort on
         * error.
         */

        status = ssam_ctrl_notif_d0_exit(c);
        if (status) {
                ssam_err(c, "pm: D0-exit notification failed: %d\n", status);
                goto err_notif;
        }

        status = ssam_irq_arm_for_wakeup(c);
        if (status)
                goto err_irq;

        WARN_ON(ssam_controller_suspend(c));
        return 0;

err_irq:
        ssam_ctrl_notif_d0_entry(c);
err_notif:
        ssam_ctrl_notif_display_on(c);
        return status;
}

static int ssam_serial_hub_pm_resume(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        WARN_ON(ssam_controller_resume(c));

        /*
         * Try to disable IRQ wakeup (if specified) and signal D0-entry. In
         * case of errors, log them and try to restore normal operation state
         * as far as possible.
         *
         * Note: Signaling display-off/display-on should normally be done from
         * some sort of display state notifier. As that is not available,
         * signal it here.
         */

        ssam_irq_disarm_wakeup(c);

        status = ssam_ctrl_notif_d0_entry(c);
        if (status)
                ssam_err(c, "pm: D0-entry notification failed: %d\n", status);

        return 0;
}

static int ssam_serial_hub_pm_freeze(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        /*
         * During hibernation image creation, we only have to ensure that the
         * EC doesn't send us any events. This is done via the display-off
         * and D0-exit notifications. Note that this sets up the wakeup IRQ
         * on the EC side, however, we have disabled it by default on our side
         * and won't enable it here.
         *
         * See ssam_serial_hub_poweroff() for more details on the hibernation
         * process.
         */

        status = ssam_ctrl_notif_d0_exit(c);
        if (status) {
                ssam_err(c, "pm: D0-exit notification failed: %d\n", status);
                ssam_ctrl_notif_display_on(c);
                return status;
        }

        WARN_ON(ssam_controller_suspend(c));
        return 0;
}

static int ssam_serial_hub_pm_thaw(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        WARN_ON(ssam_controller_resume(c));

        status = ssam_ctrl_notif_d0_entry(c);
        if (status)
                ssam_err(c, "pm: D0-exit notification failed: %d\n", status);

        return status;
}

static int ssam_serial_hub_pm_poweroff(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        /*
         * When entering hibernation and powering off the system, the EC, at
         * least on some models, may disable events. Without us taking care of
         * that, this leads to events not being enabled/restored when the
         * system resumes from hibernation, resulting SAM-HID subsystem devices
         * (i.e. keyboard, touchpad) not working, AC-plug/AC-unplug events being
         * gone, etc.
         *
         * To avoid these issues, we disable all registered events here (this is
         * likely not actually required) and restore them during the drivers PM
         * restore callback.
         *
         * Wakeup from the EC interrupt is not supported during hibernation,
         * so don't arm the IRQ here.
         */

        status = ssam_notifier_disable_registered(c);
        if (status) {
                ssam_err(c, "pm: failed to disable notifiers for hibernation: %d\n",
                         status);
                return status;
        }

        status = ssam_ctrl_notif_d0_exit(c);
        if (status) {
                ssam_err(c, "pm: D0-exit notification failed: %d\n", status);
                ssam_notifier_restore_registered(c);
                return status;
        }

        WARN_ON(ssam_controller_suspend(c));
        return 0;
}

static int ssam_serial_hub_pm_restore(struct device *dev)
{
        struct ssam_controller *c = dev_get_drvdata(dev);
        int status;

        /*
         * Ignore but log errors, try to restore state as much as possible in
         * case of failures. See ssam_serial_hub_poweroff() for more details on
         * the hibernation process.
         */

        WARN_ON(ssam_controller_resume(c));

        status = ssam_ctrl_notif_d0_entry(c);
        if (status)
                ssam_err(c, "pm: D0-entry notification failed: %d\n", status);

        ssam_notifier_restore_registered(c);
        return 0;
}

static const struct dev_pm_ops ssam_serial_hub_pm_ops = {
        .prepare  = ssam_serial_hub_pm_prepare,
        .complete = ssam_serial_hub_pm_complete,
        .suspend  = ssam_serial_hub_pm_suspend,
        .resume   = ssam_serial_hub_pm_resume,
        .freeze   = ssam_serial_hub_pm_freeze,
        .thaw     = ssam_serial_hub_pm_thaw,
        .poweroff = ssam_serial_hub_pm_poweroff,
        .restore  = ssam_serial_hub_pm_restore,
};

#else /* CONFIG_PM_SLEEP */

static const struct dev_pm_ops ssam_serial_hub_pm_ops = { };

#endif /* CONFIG_PM_SLEEP */


/* -- Device/driver setup. -------------------------------------------------- */

static const struct acpi_gpio_params gpio_ssam_wakeup_int = { 0, 0, false };
static const struct acpi_gpio_params gpio_ssam_wakeup     = { 1, 0, false };

static const struct acpi_gpio_mapping ssam_acpi_gpios[] = {
        { "ssam_wakeup-int-gpio", &gpio_ssam_wakeup_int, 1 },
        { "ssam_wakeup-gpio",     &gpio_ssam_wakeup,     1 },
        { },
};

static int ssam_serial_hub_probe(struct serdev_device *serdev)
{
        struct device *dev = &serdev->dev;
        struct acpi_device *ssh = ACPI_COMPANION(dev);
        struct ssam_controller *ctrl;
        int status;

        if (ssh) {
                status = gpiod_count(dev, NULL);
                if (status < 0)
                        return dev_err_probe(dev, status, "no GPIO found\n");

                status = devm_acpi_dev_add_driver_gpios(dev, ssam_acpi_gpios);
                if (status)
                        return status;
        }

        /* Allocate controller. */
        ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
        if (!ctrl)
                return -ENOMEM;

        /* Initialize controller. */
        status = ssam_controller_init(ctrl, serdev);
        if (status) {
                dev_err_probe(dev, status, "failed to initialize ssam controller\n");
                goto err_ctrl_init;
        }

        ssam_controller_lock(ctrl);

        /* Set up serdev device. */
        serdev_device_set_drvdata(serdev, ctrl);
        serdev_device_set_client_ops(serdev, &ssam_serdev_ops);
        status = serdev_device_open(serdev);
        if (status) {
                dev_err_probe(dev, status, "failed to open serdev device\n");
                goto err_devopen;
        }

        status = ssam_serdev_setup(ssh, serdev);
        if (status) {
                status = dev_err_probe(dev, status, "failed to setup serdev\n");
                goto err_devinit;
        }

        /* Start controller. */
        status = ssam_controller_start(ctrl);
        if (status)
                goto err_devinit;

        ssam_controller_unlock(ctrl);

        /*
         * Initial SAM requests: Log version and notify default/init power
         * states.
         */
        status = ssam_log_firmware_version(ctrl);
        if (status) {
                dev_err_probe(dev, status, "failed to get firmware version\n");
                goto err_initrq;
        }

        status = ssam_ctrl_notif_d0_entry(ctrl);
        if (status) {
                dev_err_probe(dev, status, "D0-entry notification failed\n");
                goto err_initrq;
        }

        status = ssam_ctrl_notif_display_on(ctrl);
        if (status) {
                dev_err_probe(dev, status, "display-on notification failed\n");
                goto err_initrq;
        }

        status = sysfs_create_group(&dev->kobj, &ssam_sam_group);
        if (status)
                goto err_initrq;

        /* Set up IRQ. */
        status = ssam_irq_setup(ctrl);
        if (status) {
                dev_err_probe(dev, status, "failed to setup IRQ\n");
                goto err_irq;
        }

        /* Finally, set main controller reference. */
        status = ssam_try_set_controller(ctrl);
        if (WARN_ON(status))    /* Currently, we're the only provider. */
                goto err_mainref;

        /*
         * TODO: The EC can wake up the system via the associated GPIO interrupt
         *       in multiple situations. One of which is the remaining battery
         *       capacity falling below a certain threshold. Normally, we should
         *       use the device_init_wakeup function, however, the EC also seems
         *       to have other reasons for waking up the system and it seems
         *       that Windows has additional checks whether the system should be
         *       resumed. In short, this causes some spurious unwanted wake-ups.
         *       For now let's thus default power/wakeup to false.
         */
        device_set_wakeup_capable(dev, true);

        /*
         * When using DT, we have to register the platform hub driver manually,
         * as it can't be matched based on top-level board compatible (like it
         * does the ACPI case).
         */
        if (!ssh) {
                struct platform_device *ph_pdev =
                        platform_device_register_simple("surface_aggregator_platform_hub",
                                                        0, NULL, 0);
                if (IS_ERR(ph_pdev))
                        return dev_err_probe(dev, PTR_ERR(ph_pdev),
                                             "Failed to register the platform hub driver\n");
        }

        if (ssh)
                acpi_dev_clear_dependencies(ssh);

        return 0;

err_mainref:
        ssam_irq_free(ctrl);
err_irq:
        sysfs_remove_group(&dev->kobj, &ssam_sam_group);
err_initrq:
        ssam_controller_lock(ctrl);
        ssam_controller_shutdown(ctrl);
err_devinit:
        serdev_device_close(serdev);
err_devopen:
        ssam_controller_destroy(ctrl);
        ssam_controller_unlock(ctrl);
err_ctrl_init:
        kfree(ctrl);
        return status;
}

static void ssam_serial_hub_remove(struct serdev_device *serdev)
{
        struct ssam_controller *ctrl = serdev_device_get_drvdata(serdev);
        int status;

        /* Clear static reference so that no one else can get a new one. */
        ssam_clear_controller();

        /* Disable and free IRQ. */
        ssam_irq_free(ctrl);

        sysfs_remove_group(&serdev->dev.kobj, &ssam_sam_group);
        ssam_controller_lock(ctrl);

        /* Remove all client devices. */
        ssam_remove_clients(&serdev->dev);

        /* Act as if suspending to silence events. */
        status = ssam_ctrl_notif_display_off(ctrl);
        if (status) {
                dev_err(&serdev->dev, "display-off notification failed: %d\n",
                        status);
        }

        status = ssam_ctrl_notif_d0_exit(ctrl);
        if (status) {
                dev_err(&serdev->dev, "D0-exit notification failed: %d\n",
                        status);
        }

        /* Shut down controller and remove serdev device reference from it. */
        ssam_controller_shutdown(ctrl);

        /* Shut down actual transport. */
        serdev_device_wait_until_sent(serdev, 0);
        serdev_device_close(serdev);

        /* Drop our controller reference. */
        ssam_controller_unlock(ctrl);
        ssam_controller_put(ctrl);

        device_set_wakeup_capable(&serdev->dev, false);
}

static const struct acpi_device_id ssam_serial_hub_acpi_match[] = {
        { "MSHW0084", 0 },
        { },
};
MODULE_DEVICE_TABLE(acpi, ssam_serial_hub_acpi_match);

#ifdef CONFIG_OF
static const struct of_device_id ssam_serial_hub_of_match[] = {
        { .compatible = "microsoft,surface-sam", },
        { },
};
MODULE_DEVICE_TABLE(of, ssam_serial_hub_of_match);
#endif

static struct serdev_device_driver ssam_serial_hub = {
        .probe = ssam_serial_hub_probe,
        .remove = ssam_serial_hub_remove,
        .driver = {
                .name = "surface_serial_hub",
                .acpi_match_table = ACPI_PTR(ssam_serial_hub_acpi_match),
                .of_match_table = of_match_ptr(ssam_serial_hub_of_match),
                .pm = &ssam_serial_hub_pm_ops,
                .shutdown = ssam_serial_hub_shutdown,
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        },
};


/* -- Module setup. --------------------------------------------------------- */

static int __init ssam_core_init(void)
{
        int status;

        status = ssam_bus_register();
        if (status)
                goto err_bus;

        status = ssh_ctrl_packet_cache_init();
        if (status)
                goto err_cpkg;

        status = ssam_event_item_cache_init();
        if (status)
                goto err_evitem;

        status = serdev_device_driver_register(&ssam_serial_hub);
        if (status)
                goto err_register;

        return 0;

err_register:
        ssam_event_item_cache_destroy();
err_evitem:
        ssh_ctrl_packet_cache_destroy();
err_cpkg:
        ssam_bus_unregister();
err_bus:
        return status;
}
subsys_initcall(ssam_core_init);

static void __exit ssam_core_exit(void)
{
        serdev_device_driver_unregister(&ssam_serial_hub);
        ssam_event_item_cache_destroy();
        ssh_ctrl_packet_cache_destroy();
        ssam_bus_unregister();
}
module_exit(ssam_core_exit);

MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
MODULE_DESCRIPTION("Subsystem and Surface Serial Hub driver for Surface System Aggregator Module");
MODULE_LICENSE("GPL");