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From:   Yunhui Cui <cuiyunhui@bytedance.com>
To:     conor@kernel.org, sunilvl@ventanamicro.com, ardb@kernel.org,
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        weidong.wd@bytedance.com, cuiyunhui@bytedance.com
Subject: [PATCH v3 2/4] firmware: introduce FFI for SMBIOS entry
Date:   Wed,  5 Jul 2023 19:42:49 +0800
Message-Id: <20230705114251.661-3-cuiyunhui@bytedance.com>
In-Reply-To: <20230705114251.661-1-cuiyunhui@bytedance.com>
References: <20230705114251.661-1-cuiyunhui@bytedance.com>
MIME-Version: 1.0
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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@bytedance.com>
---
 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@bytedance.com
+S:	Maintained
+F:	drivers/firmware/ffi.c
+F:	include/linux/ffi.h
+
 EXTERNAL CONNECTOR SUBSYSTEM (EXTCON)
 M:	MyungJoo Ham <myungjoo.ham@samsung.com>
 M:	Chanwoo Choi <cw00.choi@samsung.com>
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