efi_driver: provide SBI based runtime system reset

On RISC-V systems system the Supervisory Binary Interface provides system
reset and poweroff. Use it at EFI runtime.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

lib/efi_driver/Makefile

@@ -9,3 +9,4 @@ obj-y += efi_uclass.o
 ifeq ($(CONFIG_PARTITIONS),y)
 obj-y += efi_block_device.o
 endif
+obj-$(CONFIG_SYSRESET_SBI) += efi_reset_riscv.o

lib/efi_driver/efi_reset_riscv.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <efi_loader.h>
+#include <asm/sbi.h>
+
+void __efi_runtime EFIAPI efi_reset_system(enum efi_reset_type reset_type,
+					   efi_status_t reset_status,
+					   unsigned long data_size,
+					   void *reset_data)
+{
+	register unsigned long eid asm("a7") = SBI_EXT_SRST;
+	register unsigned long fid asm("a6") = SBI_EXT_SRST_RESET;
+	register unsigned long type asm("a0");
+	register unsigned long reason asm("a1") = SBI_SRST_RESET_REASON_NONE;
+
+	switch (reset_type) {
+	case EFI_RESET_WARM:
+		type = SBI_SRST_RESET_TYPE_WARM_REBOOT;
+		break;
+	case EFI_RESET_SHUTDOWN:
+		type = SBI_SRST_RESET_TYPE_SHUTDOWN;
+		break;
+	default:
+		type = SBI_SRST_RESET_TYPE_COLD_REBOOT;
+		break;
+	}
+	asm volatile ("ecall\n"
+		      : : "r" (eid), "r" (fid), "r" (type), "r" (reason));
+}

lib/efi_loader/Kconfig

@@ -366,7 +366,7 @@ config EFI_HAVE_RUNTIME_RESET
 	bool
 	default y
 	depends on ARCH_BCM283X || FSL_LAYERSCAPE || PSCI_RESET || \
-		   SANDBOX || SYSRESET_X86
+		   SANDBOX || SYSRESET_SBI || SYSRESET_X86
 
 config EFI_GRUB_ARM32_WORKAROUND
 	bool "Workaround for GRUB on 32bit ARM"