MIPS: Loongson64: Add /sys/firmware/lefi/boardinfo

Add /sys/firmware/lefi/boardinfo to get mainboard and BIOS info easily
on the Loongson platform, this is useful to point out the current used
mainboard type and BIOS version when there exists problems related with
hardware or firmware.

The related structures are already defined in the interface specification
about firmware and kernel which are common requirement and specific for
Loongson64, so only add a new boardinfo.c file in arch/mips/loongson64.

E.g. with this patch:

[loongson@linux ~]$ cat /sys/firmware/lefi/boardinfo
Board Info
Manufacturer            : LEMOTE
Board Name              : LEMOTE-LS3A4000-7A1000-1w-V01-pc
Family                  : LOONGSON3

BIOS Info
Vendor                  : Kunlun
Version                 : Kunlun-A1901-V4.1.3-20200414093938
ROM Size                : 4 KB
Release Date            : 2020-04-14

By the way, using dmidecode command can get the similar info if there
exists SMBIOS in firmware, but the fact is that there is no SMBIOS on
some machines, we can see nothing when execute dmidecode, like this:

[root@linux loongson]# dmidecode
# dmidecode 2.12
# No SMBIOS nor DMI entry point found, sorry.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/include/asm/mach-loongson64/boot_param.h

@@ -228,6 +228,10 @@ struct loongson_system_configuration {
 extern struct efi_memory_map_loongson *loongson_memmap;
 extern struct loongson_system_configuration loongson_sysconf;
 
+extern struct board_devices *eboard;
+extern struct interface_info *einter;
+extern struct loongson_special_attribute *especial;
+
 extern u32 node_id_offset;
 extern void ls7a_early_config(void);
 extern void rs780e_early_config(void);

arch/mips/loongson64/Makefile

@@ -11,3 +11,4 @@ obj-$(CONFIG_RS780_HPET) += hpet.o
 obj-$(CONFIG_SUSPEND) += pm.o
 obj-$(CONFIG_PCI_QUIRKS) += vbios_quirk.o
 obj-$(CONFIG_CPU_LOONGSON3_CPUCFG_EMULATION) += cpucfg-emul.o
+obj-$(CONFIG_SYSFS) += boardinfo.o

arch/mips/loongson64/boardinfo.c

+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kobject.h>
+#include <boot_param.h>
+
+static ssize_t boardinfo_show(struct kobject *kobj,
+			      struct kobj_attribute *attr, char *buf)
+{
+	char board_manufacturer[64] = {0};
+	char *tmp_board_manufacturer = board_manufacturer;
+	char bios_vendor[64] = {0};
+	char *tmp_bios_vendor = bios_vendor;
+
+	strcpy(board_manufacturer, eboard->name);
+	strcpy(bios_vendor, einter->description);
+
+	return sprintf(buf,
+		       "Board Info\n"
+		       "Manufacturer\t\t: %s\n"
+		       "Board Name\t\t: %s\n"
+		       "Family\t\t\t: LOONGSON3\n\n"
+		       "BIOS Info\n"
+		       "Vendor\t\t\t: %s\n"
+		       "Version\t\t\t: %s\n"
+		       "ROM Size\t\t: %d KB\n"
+		       "Release Date\t\t: %s\n",
+		       strsep(&tmp_board_manufacturer, "-"),
+		       eboard->name,
+		       strsep(&tmp_bios_vendor, "-"),
+		       einter->description,
+		       einter->size,
+		       especial->special_name);
+}
+static struct kobj_attribute boardinfo_attr = __ATTR(boardinfo, 0444,
+						     boardinfo_show, NULL);
+
+static int __init boardinfo_init(void)
+{
+	struct kobject *lefi_kobj;
+
+	lefi_kobj = kobject_create_and_add("lefi", firmware_kobj);
+	if (!lefi_kobj) {
+		pr_err("lefi: Firmware registration failed.\n");
+		return -ENOMEM;
+	}
+
+	return sysfs_create_file(lefi_kobj, &boardinfo_attr.attr);
+}
+late_initcall(boardinfo_init);

arch/mips/loongson64/env.c

@@ -28,6 +28,10 @@ EXPORT_SYMBOL(cpu_clock_freq);
 struct efi_memory_map_loongson *loongson_memmap;
 struct loongson_system_configuration loongson_sysconf;
 
+struct board_devices *eboard;
+struct interface_info *einter;
+struct loongson_special_attribute *especial;
+
 u64 loongson_chipcfg[MAX_PACKAGES] = {0xffffffffbfc00180};
 u64 loongson_chiptemp[MAX_PACKAGES];
 u64 loongson_freqctrl[MAX_PACKAGES];
@@ -57,6 +61,12 @@ void __init prom_init_env(void)
 		((u64)loongson_p + loongson_p->system_offset);
 	ecpu = (struct efi_cpuinfo_loongson *)
 		((u64)loongson_p + loongson_p->cpu_offset);
+	eboard = (struct board_devices *)
+		((u64)loongson_p + loongson_p->boarddev_table_offset);
+	einter = (struct interface_info *)
+		((u64)loongson_p + loongson_p->interface_offset);
+	especial = (struct loongson_special_attribute *)
+		((u64)loongson_p + loongson_p->special_offset);
 	eirq_source = (struct irq_source_routing_table *)
 		((u64)loongson_p + loongson_p->irq_offset);
 	loongson_memmap = (struct efi_memory_map_loongson *)