reset: Add Raspberry Pi 4 firmware reset controller

Raspberry Pi 4's co-processor controls some of the board's HW
initialization process, but it's up to Linux to trigger it when
relevant. Introduce a reset controller capable of interfacing with
RPi4's co-processor that models these firmware initialization routines as
reset lines.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>

drivers/reset/Kconfig

@@ -153,4 +153,15 @@ config RESET_SYSCON
 	depends on DM_RESET
 	help
 	  Support generic syscon mapped register reset devices.
+
+config RESET_RASPBERRYPI
+	bool "Raspberry Pi 4 Firmware Reset Controller Driver"
+	depends on DM_RESET && ARCH_BCM283X
+	default USB_XHCI_PCI
+	help
+	  Raspberry Pi 4's co-processor controls some of the board's HW
+	  initialization process, but it's up to Linux to trigger it when
+	  relevant. This driver provides a reset controller capable of
+	  interfacing with RPi4's co-processor and model these firmware
+	  initialization routines as reset lines.
 endmenu

drivers/reset/Makefile

@@ -24,3 +24,4 @@ obj-$(CONFIG_RESET_SUNXI) += reset-sunxi.o
 obj-$(CONFIG_RESET_HISILICON) += reset-hisilicon.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
 obj-$(CONFIG_RESET_SYSCON) += reset-syscon.o
+obj-$(CONFIG_RESET_RASPBERRYPI) += reset-raspberrypi.o

drivers/reset/reset-raspberrypi.c

@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Raspberry Pi 4 firmware reset driver
+ *
+ * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+ */
+#include <common.h>
+#include <dm.h>
+#include <reset-uclass.h>
+#include <asm/arch/msg.h>
+#include <dt-bindings/reset/raspberrypi,firmware-reset.h>
+
+static int raspberrypi_reset_request(struct reset_ctl *reset_ctl)
+{
+	if (reset_ctl->id >= RASPBERRYPI_FIRMWARE_RESET_NUM_IDS)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int raspberrypi_reset_free(struct reset_ctl *reset_ctl)
+{
+	return 0;
+}
+
+static int raspberrypi_reset_assert(struct reset_ctl *reset_ctl)
+{
+	switch (reset_ctl->id) {
+	case RASPBERRYPI_FIRMWARE_RESET_ID_USB:
+		bcm2711_notify_vl805_reset();
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int raspberrypi_reset_deassert(struct reset_ctl *reset_ctl)
+{
+	return 0;
+}
+
+struct reset_ops raspberrypi_reset_ops = {
+	.request = raspberrypi_reset_request,
+	.rfree = raspberrypi_reset_free,
+	.rst_assert = raspberrypi_reset_assert,
+	.rst_deassert = raspberrypi_reset_deassert,
+};
+
+static const struct udevice_id raspberrypi_reset_ids[] = {
+	{ .compatible = "raspberrypi,firmware-reset" },
+	{ }
+};
+
+U_BOOT_DRIVER(raspberrypi_reset) = {
+	.name = "raspberrypi-reset",
+	.id = UCLASS_RESET,
+	.of_match = raspberrypi_reset_ids,
+	.ops = &raspberrypi_reset_ops,
+};
+

include/dt-bindings/reset/raspberrypi,firmware-reset.h

@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2020 Nicolas Saenz Julienne
+ * Author: Nicolas Saenz Julienne <nsaenzjulienne@suse.com>
+ */
+
+#ifndef _DT_BINDINGS_RASPBERRYPI_FIRMWARE_RESET_H
+#define _DT_BINDINGS_RASPBERRYPI_FIRMWARE_RESET_H
+
+#define RASPBERRYPI_FIRMWARE_RESET_ID_USB	0
+#define RASPBERRYPI_FIRMWARE_RESET_NUM_IDS	1
+
+#endif