riscv/efi_stub: Add support for RISCV_EFI_BOOT_PROTOCOL

Add support for getting the boot hart ID from the Linux EFI stub using
RISCV_EFI_BOOT_PROTOCOL. This method is preferred over the existing DT
based approach since it works irrespective of DT or ACPI.

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>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Link: https://lore.kernel.org/r/20220519051512.136724-2-sunilvl@ventanamicro.com
[ardb: minor tweaks for coding style and whitespace]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

2 files changed, 30 insertions, 6 deletions

diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index a0477afaa55f..b0ae0a454404 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -794,6 +794,13 @@ union efi_tcg2_protocol {
 	} mixed_mode;
 };
 
+struct riscv_efi_boot_protocol {
+	u64 revision;
+
+	efi_status_t (__efiapi *get_boot_hartid)(struct riscv_efi_boot_protocol *,
+						 unsigned long *boot_hartid);
+};
+
 typedef union efi_load_file_protocol efi_load_file_protocol_t;
 typedef union efi_load_file_protocol efi_load_file2_protocol_t;
 
diff --git a/drivers/firmware/efi/libstub/riscv-stub.c b/drivers/firmware/efi/libstub/riscv-stub.c
index eec043873354..9e85e58d1f27 100644
--- a/drivers/firmware/efi/libstub/riscv-stub.c
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -21,9 +21,9 @@
 #define MIN_KIMG_ALIGN		SZ_4M
 #endif
 
-typedef void __noreturn (*jump_kernel_func)(unsigned int, unsigned long);
+typedef void __noreturn (*jump_kernel_func)(unsigned long, unsigned long);
 
-static u32 hartid;
+static unsigned long hartid;
 
 static int get_boot_hartid_from_fdt(void)
 {
@@ -47,14 +47,31 @@ static int get_boot_hartid_from_fdt(void)
 	return 0;
 }
 
+static efi_status_t get_boot_hartid_from_efi(void)
+{
+	efi_guid_t boot_protocol_guid = RISCV_EFI_BOOT_PROTOCOL_GUID;
+	struct riscv_efi_boot_protocol *boot_protocol;
+	efi_status_t status;
+
+	status = efi_bs_call(locate_protocol, &boot_protocol_guid, NULL,
+			     (void **)&boot_protocol);
+	if (status != EFI_SUCCESS)
+		return status;
+	return efi_call_proto(boot_protocol, get_boot_hartid, &hartid);
+}
+
 efi_status_t check_platform_features(void)
 {
+	efi_status_t status;
 	int ret;
 
-	ret = get_boot_hartid_from_fdt();
-	if (ret) {
-		efi_err("/chosen/boot-hartid missing or invalid!\n");
-		return EFI_UNSUPPORTED;
+	status = get_boot_hartid_from_efi();
+	if (status != EFI_SUCCESS) {
+		ret = get_boot_hartid_from_fdt();
+		if (ret) {
+			efi_err("Failed to get boot hartid!\n");
+			return EFI_UNSUPPORTED;
+		}
 	}
 	return EFI_SUCCESS;
 }