riscv: dmi: Add SMBIOS/DMI support

Enable the dmi driver for riscv which would allow access the
SMBIOS info through some userspace file(/sys/firmware/dmi/*).

The change was based on that of arm64 and has been verified
by dmidecode tool.
Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20240613065507.287577-1-haibo1.xu@intel.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Kconfig

@@ -967,6 +967,17 @@ config EFI
 	  allow the kernel to be booted as an EFI application. This
 	  is only useful on systems that have UEFI firmware.
 
+config DMI
+	bool "Enable support for SMBIOS (DMI) tables"
+	depends on EFI
+	default y
+	help
+	  This enables SMBIOS/DMI feature for systems.
+
+	  This option is only useful on systems that have UEFI firmware.
+	  However, even with this option, the resultant kernel should
+	  continue to boot on existing non-UEFI platforms.
+
 config CC_HAVE_STACKPROTECTOR_TLS
 	def_bool $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=tp -mstack-protector-guard-offset=0)
 

arch/riscv/include/asm/dmi.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2024 Intel Corporation
+ *
+ * based on arch/arm64/include/asm/dmi.h
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef __ASM_DMI_H
+#define __ASM_DMI_H
+
+#include <linux/io.h>
+#include <linux/slab.h>
+
+#define dmi_early_remap(x, l)		memremap(x, l, MEMREMAP_WB)
+#define dmi_early_unmap(x, l)		memunmap(x)
+#define dmi_remap(x, l)			memremap(x, l, MEMREMAP_WB)
+#define dmi_unmap(x)			memunmap(x)
+#define dmi_alloc(l)			kzalloc(l, GFP_KERNEL)
+
+#endif

drivers/firmware/efi/riscv-runtime.c

@@ -152,3 +152,16 @@ void arch_efi_call_virt_teardown(void)
 {
 	efi_virtmap_unload();
 }
+
+static int __init riscv_dmi_init(void)
+{
+	/*
+	 * On riscv, DMI depends on UEFI, and dmi_setup() needs to
+	 * be called early because dmi_id_init(), which is an arch_initcall
+	 * itself, depends on dmi_scan_machine() having been called already.
+	 */
+	dmi_setup();
+
+	return 0;
+}
+core_initcall(riscv_dmi_init);