[PATCH v3 2/4] firmware: introduce FFI for SMBIOS entry

From: Yunhui Cui
Date: Wed Jul 05 2023 - 07:45:03 EST

To enable DMI functionality on platforms where the bootloader
does not support EFI and the architecture does not support
reserved addresses.

Add a "ffitbl" device tree node to find the SMBIOS entry
point and use wire up dmi_scan_machine().This feature is
known as the FDT Firmware Interface (FFI).

Signed-off-by: Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx>
---
MAINTAINERS | 6 +++
drivers/firmware/Kconfig | 11 +++++
drivers/firmware/Makefile | 1 +
drivers/firmware/dmi_scan.c | 97 ++++++++++++++++++++++---------------
drivers/firmware/ffi.c | 42 ++++++++++++++++
include/linux/ffi.h | 29 +++++++++++
6 files changed, 146 insertions(+), 40 deletions(-)
create mode 100644 drivers/firmware/ffi.c
create mode 100644 include/linux/ffi.h

diff --git a/MAINTAINERS b/MAINTAINERS
index e592f489e757..9b886ef36587 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7871,6 +7871,12 @@ F: arch/x86/platform/efi/
F: drivers/firmware/efi/
F: include/linux/efi*.h

+FDT FIRMWARE INTERFACE (FFI)
+M: Yunhui Cui cuiyunhui@xxxxxxxxxxxxx
+S: Maintained
+F: drivers/firmware/ffi.c
+F: include/linux/ffi.h
+
EXTERNAL CONNECTOR SUBSYSTEM (EXTCON)
M: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
M: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index b59e3041fd62..3579d9bc22ff 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -303,6 +303,17 @@ config TURRIS_MOX_RWTM
other manufacturing data and also utilize the Entropy Bit Generator
for hardware random number generation.

+config FDT_FW_INTERFACE
+ bool "An interface for passing firmware info through FDT"
+ depends on OF && OF_FLATTREE
+ default n
+ help
+ Enable this option to support the transfer of firmware information,
+ such as smbios tables, for bootloaders that do not support EFI, such
+ as coreboot.
+
+ Say Y here if you want to transfer firmware information by FDT.
+
source "drivers/firmware/arm_ffa/Kconfig"
source "drivers/firmware/broadcom/Kconfig"
source "drivers/firmware/cirrus/Kconfig"
diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index 28fcddcd688f..3b8b5d0868a6 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -33,6 +33,7 @@ obj-y += cirrus/
obj-y += meson/
obj-$(CONFIG_GOOGLE_FIRMWARE) += google/
obj-y += efi/
+obj-$(CONFIG_FDT_FW_INTERFACE) += ffi.o
obj-y += imx/
obj-y += psci/
obj-y += smccc/
diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 015c95a825d3..c29ea050b5b9 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -6,6 +6,7 @@
#include <linux/ctype.h>
#include <linux/dmi.h>
#include <linux/efi.h>
+#include <linux/ffi.h>
#include <linux/memblock.h>
#include <linux/random.h>
#include <asm/dmi.h>
@@ -655,54 +656,70 @@ static int __init dmi_smbios3_present(const u8 *buf)
return 1;
}

-static void __init dmi_scan_machine(void)
+/*
+ * According to the DMTF SMBIOS reference spec v3.0.0, it is
+ * allowed to define both the 64-bit entry point (smbios3) and
+ * the 32-bit entry point (smbios), in which case they should
+ * either both point to the same SMBIOS structure table, or the
+ * table pointed to by the 64-bit entry point should contain a
+ * superset of the table contents pointed to by the 32-bit entry
+ * point (section 5.2)
+ * This implies that the 64-bit entry point should have
+ * precedence if it is defined and supported by the OS. If we
+ * have the 64-bit entry point, but fail to decode it, fall
+ * back to the legacy one (if available)
+ */
+static int __init dmi_sacn_smbios(unsigned long smbios3, unsigned long smbios)
{
- char __iomem *p, *q;
+ char __iomem *p;
char buf[32];
-
- if (efi_enabled(EFI_CONFIG_TABLES)) {
- /*
- * According to the DMTF SMBIOS reference spec v3.0.0, it is
- * allowed to define both the 64-bit entry point (smbios3) and
- * the 32-bit entry point (smbios), in which case they should
- * either both point to the same SMBIOS structure table, or the
- * table pointed to by the 64-bit entry point should contain a
- * superset of the table contents pointed to by the 32-bit entry
- * point (section 5.2)
- * This implies that the 64-bit entry point should have
- * precedence if it is defined and supported by the OS. If we
- * have the 64-bit entry point, but fail to decode it, fall
- * back to the legacy one (if available)
- */
- if (efi.smbios3 != EFI_INVALID_TABLE_ADDR) {
- p = dmi_early_remap(efi.smbios3, 32);
- if (p == NULL)
- goto error;
- memcpy_fromio(buf, p, 32);
- dmi_early_unmap(p, 32);
-
- if (!dmi_smbios3_present(buf)) {
- dmi_available = 1;
- return;
- }
- }
- if (efi.smbios == EFI_INVALID_TABLE_ADDR)
- goto error;
-
- /* This is called as a core_initcall() because it isn't
- * needed during early boot. This also means we can
- * iounmap the space when we're done with it.
- */
- p = dmi_early_remap(efi.smbios, 32);
+ #define INVALID_TABLE_ADDR (~0UL)
+ if (smbios3 != INVALID_TABLE_ADDR) {
+ p = dmi_early_remap(smbios3, 32);
if (p == NULL)
- goto error;
+ return -1;
memcpy_fromio(buf, p, 32);
dmi_early_unmap(p, 32);

- if (!dmi_present(buf)) {
+ if (!dmi_smbios3_present(buf)) {
dmi_available = 1;
- return;
+ return 0;
}
+ }
+ if (smbios == INVALID_TABLE_ADDR)
+ return -1;
+ /*
+ * This is called as a core_initcall() because it isn't
+ * needed during early boot. This also means we can
+ * iounmap the space when we're done with it.
+ */
+ p = dmi_early_remap(smbios, 32);
+ if (p == NULL)
+ return -1;
+ memcpy_fromio(buf, p, 32);
+ dmi_early_unmap(p, 32);
+
+ if (!dmi_present(buf)) {
+ dmi_available = 1;
+ return 0;
+ }
+
+ return -1;
+}
+
+static void __init dmi_scan_machine(void)
+{
+ char __iomem *p, *q;
+ char buf[32];
+
+ if (ffi_enabled(FFI_CONFIG_TABLES)) {
+ if (!dmi_sacn_smbios(ffi.smbios3, ffi.smbios))
+ return;
+ }
+
+ if (efi_enabled(EFI_CONFIG_TABLES)) {
+ if (dmi_sacn_smbios(efi.smbios3, efi.smbios))
+ goto error;
} else if (IS_ENABLED(CONFIG_DMI_SCAN_MACHINE_NON_EFI_FALLBACK)) {
p = dmi_early_remap(SMBIOS_ENTRY_POINT_SCAN_START, 0x10000);
if (p == NULL)
diff --git a/drivers/firmware/ffi.c b/drivers/firmware/ffi.c
new file mode 100644
index 000000000000..d4994a22438b
--- /dev/null
+++ b/drivers/firmware/ffi.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/libfdt.h>
+#include <linux/ffi.h>
+
+#define FFI_INVALID_TABLE_ADDR (~0UL)
+
+struct ffi __read_mostly ffi = {
+ .smbios = FFI_INVALID_TABLE_ADDR,
+ .smbios3 = FFI_INVALID_TABLE_ADDR,
+};
+
+void __init ffi_smbios_root_pointer(void)
+{
+ u32 ffitbl, smbios, len, ver;
+ u64 entry;
+ fdt64_t *prop;
+
+ ffitbl = fdt_subnode_offset(initial_boot_params, 0, "ffitbl");
+ smbios = fdt_subnode_offset(initial_boot_params, ffitbl, "smbios");
+ prop = fdt_getprop_w(initial_boot_params, smbios, "entry", &len);
+ if (!prop || len != sizeof(u64)) {
+ pr_debug("smbios entry not found.\n");
+ return;
+ }
+ entry = fdt64_to_cpu(*prop);
+
+ prop = fdt_getprop_w(initial_boot_params, smbios, "reg", &len);
+ if (!prop || len != sizeof(u32)) {
+ pr_debug("smbios reg not found.\n");
+ return;
+ }
+ ver = fdt32_to_cpu(*prop);
+ (ver == 3) ? (ffi.smbios3 = entry) : (ffi.smbios = entry);
+ set_bit(FFI_CONFIG_TABLES, &ffi.flags);
+ pr_debug("smbios%d entry: %llx\n", ver, entry);
+}
+
diff --git a/include/linux/ffi.h b/include/linux/ffi.h
new file mode 100644
index 000000000000..a99c2a290556
--- /dev/null
+++ b/include/linux/ffi.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_FFI_H
+#define _LINUX_FFI_H
+
+extern struct ffi {
+ unsigned long smbios; /* SMBIOS table (32 bit entry point) */
+ unsigned long smbios3; /* SMBIOS table (64 bit entry point) */
+ unsigned long flags;
+
+} ffi;
+
+#define FFI_CONFIG_TABLES 2 /* Can we use FFI config tables? */
+
+#ifdef CONFIG_FDT_FW_INTERFACE
+extern void ffi_smbios_root_pointer(void);
+static inline bool ffi_enabled(int feature)
+{
+ return test_bit(feature, &ffi.flags) != 0;
+}
+#else
+static inline bool ffi_enabled(int feature)
+{
+ return false;
+}
+void ffi_smbios_root_pointer(void) { return; };
+#endif
+
+#endif /* _LINUX_FFI_H */
--
2.20.1