sysreset: psci: support system reset in a generic way with PSCI

If the system is running PSCI firmware, the System Reset function
(func ID: 0x80000009) is supposed to be handled by PSCI, that is,
the SoC/board specific reset implementation should be moved to PSCI.
U-Boot should call the PSCI service according to the arm-smccc
manner.

The arm-smccc is supported on ARMv7 or later.  Especially, ARMv8
generation SoCs are likely to run ARM Trusted Firmware BL31.  In
this case, U-Boot is a non-secure world boot loader, so it should
not be able to reset the system directly.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

drivers/firmware/psci.c

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2017 Masahiro Yamada <yamada.masahiro@socionext.com>
+ *
+ * Based on drivers/firmware/psci.c from Linux:
+ * Copyright (C) 2015 ARM Limited
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm/device.h>
+#include <dm/lists.h>
+#include <libfdt.h>
+#include <linux/arm-smccc.h>
+#include <linux/errno.h>
+#include <linux/psci.h>
+
+psci_fn *invoke_psci_fn;
+
+static unsigned long __invoke_psci_fn_hvc(unsigned long function_id,
+			unsigned long arg0, unsigned long arg1,
+			unsigned long arg2)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_hvc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
+	return res.a0;
+}
+
+static unsigned long __invoke_psci_fn_smc(unsigned long function_id,
+			unsigned long arg0, unsigned long arg1,
+			unsigned long arg2)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
+	return res.a0;
+}
+
+static int psci_bind(struct udevice *dev)
+{
+	/* No SYSTEM_RESET support for PSCI 0.1 */
+	if (of_device_is_compatible(dev, "arm,psci-0.2") ||
+	    of_device_is_compatible(dev, "arm,psci-1.0")) {
+		int ret;
+
+		/* bind psci-sysreset optionally */
+		ret = device_bind_driver(dev, "psci-sysreset", "psci-sysreset",
+					 NULL);
+		if (ret)
+			debug("PSCI System Reset was not bound.\n");
+	}
+
+	return 0;
+}
+
+static int psci_probe(struct udevice *dev)
+{
+	DECLARE_GLOBAL_DATA_PTR;
+	const char *method;
+
+	method = fdt_stringlist_get(gd->fdt_blob, dev->of_offset, "method", 0,
+				    NULL);
+	if (!method) {
+		printf("missing \"method\" property\n");
+		return -ENXIO;
+	}
+
+	if (!strcmp("hvc", method)) {
+		invoke_psci_fn = __invoke_psci_fn_hvc;
+	} else if (!strcmp("smc", method)) {
+		invoke_psci_fn = __invoke_psci_fn_smc;
+	} else {
+		printf("invalid \"method\" property: %s\n", method);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct udevice_id psci_of_match[] = {
+	{ .compatible = "arm,psci" },
+	{ .compatible = "arm,psci-0.2" },
+	{ .compatible = "arm,psci-1.0" },
+	{},
+};
+
+U_BOOT_DRIVER(psci) = {
+	.name = "psci",
+	.id = UCLASS_FIRMWARE,
+	.of_match = psci_of_match,
+	.bind = psci_bind,
+	.probe = psci_probe,
+};