// SPDX-License-Identifier: GPL-2.0
/*
 * Raspberry Pi 4 firmware reset driver
 *
 * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
 */
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/reset-controller.h>
#include <soc/bcm2835/raspberrypi-firmware.h>
#include <dt-bindings/reset/raspberrypi,firmware-reset.h>

struct rpi_reset {
        struct reset_controller_dev rcdev;
        struct rpi_firmware *fw;
};

static inline struct rpi_reset *to_rpi(struct reset_controller_dev *rcdev)
{
        return container_of(rcdev, struct rpi_reset, rcdev);
}

static int rpi_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
{
        struct rpi_reset *priv = to_rpi(rcdev);
        u32 dev_addr;
        int ret;

        switch (id) {
        case RASPBERRYPI_FIRMWARE_RESET_ID_USB:
                /*
                 * The Raspberry Pi 4 gets its USB functionality from VL805, a
                 * PCIe chip that implements xHCI. After a PCI reset, VL805's
                 * firmware may either be loaded directly from an EEPROM or, if
                 * not present, by the SoC's co-processor, VideoCore. rpi's
                 * VideoCore OS contains both the non public firmware load
                 * logic and the VL805 firmware blob. This triggers the
                 * aforementioned process.
                 *
                 * The pci device address is expected is expected by the
                 * firmware encoded like this:
                 *
                 *      PCI_BUS << 20 | PCI_SLOT << 15 | PCI_FUNC << 12
                 *
                 * But since rpi's PCIe is hardwired, we know the address in
                 * advance.
                 */
                dev_addr = 0x100000;
                ret = rpi_firmware_property(priv->fw, RPI_FIRMWARE_NOTIFY_XHCI_RESET,
                                            &dev_addr, sizeof(dev_addr));
                if (ret)
                        return ret;

                /* Wait for vl805 to startup */
                usleep_range(200, 1000);
                break;

        default:
                return -EINVAL;
        }

        return 0;
}

static const struct reset_control_ops rpi_reset_ops = {
        .reset  = rpi_reset_reset,
};

static int rpi_reset_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct rpi_firmware *fw;
        struct device_node *np;
        struct rpi_reset *priv;

        np = of_get_parent(dev->of_node);
        if (!np) {
                dev_err(dev, "Missing firmware node\n");
                return -ENOENT;
        }

        fw = devm_rpi_firmware_get(&pdev->dev, np);
        of_node_put(np);
        if (!fw)
                return -EPROBE_DEFER;

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

        dev_set_drvdata(dev, priv);

        priv->fw = fw;
        priv->rcdev.owner = THIS_MODULE;
        priv->rcdev.nr_resets = RASPBERRYPI_FIRMWARE_RESET_NUM_IDS;
        priv->rcdev.ops = &rpi_reset_ops;
        priv->rcdev.of_node = dev->of_node;

        return devm_reset_controller_register(dev, &priv->rcdev);
}

static const struct of_device_id rpi_reset_of_match[] = {
        { .compatible = "raspberrypi,firmware-reset" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, rpi_reset_of_match);

static struct platform_driver rpi_reset_driver = {
        .probe  = rpi_reset_probe,
        .driver = {
                .name = "raspberrypi-reset",
                .of_match_table = rpi_reset_of_match,
        },
};
module_platform_driver(rpi_reset_driver);

MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
MODULE_DESCRIPTION("Raspberry Pi 4 firmware reset driver");
MODULE_LICENSE("GPL");