1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Raspberry Pi 4 firmware reset driver
  4 *
  5 * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
  6 */
  7#include <linux/delay.h>
  8#include <linux/device.h>
  9#include <linux/module.h>
 10#include <linux/of.h>
 11#include <linux/platform_device.h>
 12#include <linux/reset-controller.h>
 13#include <soc/bcm2835/raspberrypi-firmware.h>
 14#include <dt-bindings/reset/raspberrypi,firmware-reset.h>
 15
 16struct rpi_reset {
 17	struct reset_controller_dev rcdev;
 18	struct rpi_firmware *fw;
 19};
 20
 21static inline struct rpi_reset *to_rpi(struct reset_controller_dev *rcdev)
 22{
 23	return container_of(rcdev, struct rpi_reset, rcdev);
 24}
 25
 26static int rpi_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
 27{
 28	struct rpi_reset *priv = to_rpi(rcdev);
 29	u32 dev_addr;
 30	int ret;
 31
 32	switch (id) {
 33	case RASPBERRYPI_FIRMWARE_RESET_ID_USB:
 34		/*
 35		 * The Raspberry Pi 4 gets its USB functionality from VL805, a
 36		 * PCIe chip that implements xHCI. After a PCI reset, VL805's
 37		 * firmware may either be loaded directly from an EEPROM or, if
 38		 * not present, by the SoC's co-processor, VideoCore. rpi's
 39		 * VideoCore OS contains both the non public firmware load
 40		 * logic and the VL805 firmware blob. This triggers the
 41		 * aforementioned process.
 42		 *
 43		 * The pci device address is expected is expected by the
 44		 * firmware encoded like this:
 45		 *
 46		 *	PCI_BUS << 20 | PCI_SLOT << 15 | PCI_FUNC << 12
 47		 *
 48		 * But since rpi's PCIe is hardwired, we know the address in
 49		 * advance.
 50		 */
 51		dev_addr = 0x100000;
 52		ret = rpi_firmware_property(priv->fw, RPI_FIRMWARE_NOTIFY_XHCI_RESET,
 53					    &dev_addr, sizeof(dev_addr));
 54		if (ret)
 55			return ret;
 56
 57		/* Wait for vl805 to startup */
 58		usleep_range(200, 1000);
 59		break;
 60
 61	default:
 62		return -EINVAL;
 63	}
 64
 65	return 0;
 66}
 67
 68static const struct reset_control_ops rpi_reset_ops = {
 69	.reset	= rpi_reset_reset,
 70};
 71
 72static int rpi_reset_probe(struct platform_device *pdev)
 73{
 74	struct device *dev = &pdev->dev;
 75	struct rpi_firmware *fw;
 76	struct device_node *np;
 77	struct rpi_reset *priv;
 78
 79	np = of_get_parent(dev->of_node);
 80	if (!np) {
 81		dev_err(dev, "Missing firmware node\n");
 82		return -ENOENT;
 83	}
 84
 85	fw = devm_rpi_firmware_get(&pdev->dev, np);
 86	of_node_put(np);
 87	if (!fw)
 88		return -EPROBE_DEFER;
 89
 90	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 91	if (!priv)
 92		return -ENOMEM;
 93
 94	dev_set_drvdata(dev, priv);
 95
 96	priv->fw = fw;
 97	priv->rcdev.owner = THIS_MODULE;
 98	priv->rcdev.nr_resets = RASPBERRYPI_FIRMWARE_RESET_NUM_IDS;
 99	priv->rcdev.ops = &rpi_reset_ops;
100	priv->rcdev.of_node = dev->of_node;
101
102	return devm_reset_controller_register(dev, &priv->rcdev);
103}
104
105static const struct of_device_id rpi_reset_of_match[] = {
106	{ .compatible = "raspberrypi,firmware-reset" },
107	{ /* sentinel */ }
108};
109MODULE_DEVICE_TABLE(of, rpi_reset_of_match);
110
111static struct platform_driver rpi_reset_driver = {
112	.probe	= rpi_reset_probe,
113	.driver	= {
114		.name = "raspberrypi-reset",
115		.of_match_table = rpi_reset_of_match,
116	},
117};
118module_platform_driver(rpi_reset_driver);
119
120MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
121MODULE_DESCRIPTION("Raspberry Pi 4 firmware reset driver");
122MODULE_LICENSE("GPL");