linux/drivers/reset/reset-raspberrypi.c

// 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 = rpi_firmware_get(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");