efi_loader: Enable RISCV_EFI_BOOT_PROTOCOL support

This adds support for new RISCV_EFI_BOOT_PROTOCOL to
communicate the boot hart ID to bootloader/kernel on RISC-V
UEFI platforms.

The specification of the protocol is hosted at:
https://github.com/riscv-non-isa/riscv-uefi

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

4 files changed, 77 insertions, 0 deletions

diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 24f9a2bb75..e5e35fe51f 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -369,4 +369,14 @@ config EFI_ESRT
 	help
 	  Enabling this option creates the ESRT UEFI system table.
 
+config EFI_RISCV_BOOT_PROTOCOL
+	bool "RISCV_EFI_BOOT_PROTOCOL support"
+	default y
+	depends on RISCV
+	help
+	  The EFI_RISCV_BOOT_PROTOCOL is used to transfer the boot hart ID
+	  to the next boot stage. It should be enabled as it is meant to
+	  replace the transfer via the device-tree. The latter is not
+	  possible on systems using ACPI.
+
 endif
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index fd344cea29..b2c664d108 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -62,6 +62,7 @@ obj-$(CONFIG_GENERATE_ACPI_TABLE) += efi_acpi.o
 obj-$(CONFIG_GENERATE_SMBIOS_TABLE) += efi_smbios.o
 obj-$(CONFIG_EFI_RNG_PROTOCOL) += efi_rng.o
 obj-$(CONFIG_EFI_TCG2_PROTOCOL) += efi_tcg2.o
+obj-$(CONFIG_EFI_RISCV_BOOT_PROTOCOL) += efi_riscv.o
 obj-$(CONFIG_EFI_LOAD_FILE2_INITRD) += efi_load_initrd.o
 obj-$(CONFIG_EFI_SIGNATURE_SUPPORT) += efi_signature.o
 
diff --git a/lib/efi_loader/efi_riscv.c b/lib/efi_loader/efi_riscv.c
new file mode 100644
index 0000000000..bccfefd8fb
--- /dev/null
+++ b/lib/efi_loader/efi_riscv.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Defines APIs that allow an OS to interact with UEFI firmware to query
+ * information about the boot hart ID.
+ *
+ * Copyright (c) 2022, Ventana Micro Systems Inc
+ */
+
+#define LOG_CATEGORY LOGC_EFI
+#include <common.h>
+#include <efi_loader.h>
+#include <efi_variable.h>
+#include <log.h>
+#include <asm/global_data.h>
+#include <efi_riscv.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+static const efi_guid_t efi_guid_riscv_boot_protocol = RISCV_EFI_BOOT_PROTOCOL_GUID;
+
+/**
+ * efi_riscv_get_boot_hartid() - return boot hart ID
+ * @this:		RISCV_EFI_BOOT_PROTOCOL instance
+ * @boot_hartid:	caller allocated memory to return boot hart id
+ * Return:		status code
+ */
+static efi_status_t EFIAPI
+efi_riscv_get_boot_hartid(struct riscv_efi_boot_protocol *this,
+			  efi_uintn_t *boot_hartid)
+{
+	EFI_ENTRY("%p, %p",  this, boot_hartid);
+
+	if (this != &riscv_efi_boot_prot || !boot_hartid)
+		return EFI_INVALID_PARAMETER;
+
+	*boot_hartid = gd->arch.boot_hart;
+
+	return EFI_EXIT(EFI_SUCCESS);
+}
+
+struct riscv_efi_boot_protocol riscv_efi_boot_prot = {
+	.revision = RISCV_EFI_BOOT_PROTOCOL_REVISION,
+	.get_boot_hartid = efi_riscv_get_boot_hartid
+};
+
+/**
+ * efi_riscv_register() - register RISCV_EFI_BOOT_PROTOCOL
+ *
+ * Return:	status code
+ */
+efi_status_t efi_riscv_register(void)
+{
+	efi_status_t ret = EFI_SUCCESS;
+
+	ret = efi_add_protocol(efi_root, &efi_guid_riscv_boot_protocol,
+			       (void *)&riscv_efi_boot_prot);
+	if (ret != EFI_SUCCESS)
+		log_err("Cannot install RISCV_EFI_BOOT_PROTOCOL\n");
+	return ret;
+}
diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
index 49172e3579..380adc15c8 100644
--- a/lib/efi_loader/efi_setup.c
+++ b/lib/efi_loader/efi_setup.c
@@ -247,6 +247,12 @@ efi_status_t efi_init_obj_list(void)
 			goto out;
 	}
 
+	if (IS_ENABLED(CONFIG_EFI_RISCV_BOOT_PROTOCOL)) {
+		ret = efi_riscv_register();
+		if (ret != EFI_SUCCESS)
+			goto out;
+	}
+
 	/* Secure boot */
 	ret = efi_init_secure_boot();
 	if (ret != EFI_SUCCESS)