[RFC PATCH 1/1] riscv/efi_stub: Add support for RISCV_EFI_BOOT_PROTOCOL

[Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>]

This patch adds the support for getting the boot hart ID in
Linux EFI stub using RISCV_EFI_BOOT_PROTOCOL.

Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
---
 drivers/firmware/efi/libstub/efistub.h    | 15 ++++++++++++
 drivers/firmware/efi/libstub/riscv-stub.c | 28 ++++++++++++++++++++---
 include/linux/efi.h                       |  1 +
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index edb77b0621ea..0428f8816942 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -720,6 +720,21 @@ union efi_tcg2_protocol {
 	} mixed_mode;
 };
 
+typedef union riscv_efi_boot_protocol riscv_efi_boot_protocol_t;
+
+union riscv_efi_boot_protocol {
+	struct {
+		u64 revision;
+		efi_status_t (__efiapi *get_boot_hartid)(
+							 riscv_efi_boot_protocol_t *,
+							 size_t *);
+	};
+	struct {
+		u32 revision;
+		u32 get_boot_hartid;
+	} mixed_mode;
+};
+
 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 380e4e251399..c7add4eb5453 100644
--- a/drivers/firmware/efi/libstub/riscv-stub.c
+++ b/drivers/firmware/efi/libstub/riscv-stub.c
@@ -46,12 +46,34 @@ static u32 get_boot_hartid_from_fdt(void)
 	return fdt32_to_cpu(*prop);
 }
 
+static u32 get_boot_hartid_from_efi(void)
+{
+	efi_guid_t boot_protocol_guid = RISCV_EFI_BOOT_PROTOCOL_GUID;
+	efi_status_t status;
+	riscv_efi_boot_protocol_t *boot_protocol;
+	size_t boot_hart_id;
+
+	status = efi_bs_call(locate_protocol, &boot_protocol_guid, NULL,
+			     (void **)&boot_protocol);
+	if (status == EFI_SUCCESS) {
+		status = efi_call_proto(boot_protocol,
+					get_boot_hartid, &boot_hart_id);
+		if (status == EFI_SUCCESS) {
+			return (u32)boot_hart_id;
+		}
+	}
+	return U32_MAX;
+}
+
 efi_status_t check_platform_features(void)
 {
-	hartid = get_boot_hartid_from_fdt();
+	hartid = get_boot_hartid_from_efi();
 	if (hartid == U32_MAX) {
-		efi_err("/chosen/boot-hartid missing or invalid!\n");
-		return EFI_UNSUPPORTED;
+		hartid = get_boot_hartid_from_fdt();
+		if (hartid == U32_MAX) {
+			efi_err("/chosen/boot-hartid missing or invalid!\n");
+			return EFI_UNSUPPORTED;
+		}
 	}
 	return EFI_SUCCESS;
 }
diff --git a/include/linux/efi.h b/include/linux/efi.h
index ccd4d3f91c98..9822c730207c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -380,6 +380,7 @@ void efi_native_runtime_setup(void);
 #define EFI_CONSOLE_OUT_DEVICE_GUID		EFI_GUID(0xd3b36f2c, 0xd551, 0x11d4,  0x9a, 0x46, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
 #define APPLE_PROPERTIES_PROTOCOL_GUID		EFI_GUID(0x91bd12fe, 0xf6c3, 0x44fb,  0xa5, 0xb7, 0x51, 0x22, 0xab, 0x30, 0x3a, 0xe0)
 #define EFI_TCG2_PROTOCOL_GUID			EFI_GUID(0x607f766c, 0x7455, 0x42be,  0x93, 0x0b, 0xe4, 0xd7, 0x6d, 0xb2, 0x72, 0x0f)
+#define RISCV_EFI_BOOT_PROTOCOL_GUID		EFI_GUID(0xccd15fec, 0x6f73, 0x4eec,  0x83, 0x95, 0x3e, 0x69, 0xe4, 0xb9, 0x40, 0xbf)
 #define EFI_LOAD_FILE_PROTOCOL_GUID		EFI_GUID(0x56ec3091, 0x954c, 0x11d2,  0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b)
 #define EFI_LOAD_FILE2_PROTOCOL_GUID		EFI_GUID(0x4006c0c1, 0xfcb3, 0x403e,  0x99, 0x6d, 0x4a, 0x6c, 0x87, 0x24, 0xe0, 0x6d)
 #define EFI_RT_PROPERTIES_TABLE_GUID		EFI_GUID(0xeb66918a, 0x7eef, 0x402a,  0x84, 0x2e, 0x93, 0x1d, 0x21, 0xc3, 0x8a, 0xe9)
-- 
2.25.1