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Wed, 22 Oct 2025 01:21:56 -0700 (PDT) Received: from adriana-show-mem3.sjc.aristanetworks.com ([74.123.28.13]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-33e223cba14sm1854292a91.2.2025.10.22.01.21.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Oct 2025 01:21:55 -0700 (PDT) From: adriana@arista.com To: linux-arm-kernel@lists.infradead.org, jdelvare@suse.com, devicetree@vger.kernel.org, robh+dt@kernel.org, frowand.list@gmail.com Cc: linux-kernel@vger.kernel.org, vasilykh@arista.com, Adriana Nicolae Subject: [PATCH 1/1] DMI: Scan for DMI table from DTS info Date: Wed, 22 Oct 2025 01:21:29 -0700 Message-ID: <20251022082129.138217-1-adriana@arista.com> X-Mailer: git-send-email 2.47.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251022_012157_866495_87DD9015 X-CRM114-Status: GOOD ( 16.96 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Some bootloaders like U-boot, particularly for the ARM architecture, provide SMBIOS/DMI tables at a specific memory address. However, these systems often do not boot using a full UEFI environment, which means the kernel's standard EFI DMI scanner cannot find these tables. The bootloader can specify the physical addresses of the SMBIOS and SMBIOS3 tables in the /chosen node using the "linux,smbios-table" and linux,smbios3-table properties. This patch hooks into the DMI initialization process to read these properties, map the tables, and parse the DMI information. This extra scan is performed after the standard EFI check fails but before the fallback memory scan, not to alter the order of DMI scanning for current implementation. Signed-off-by: Adriana Nicolae diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c index 70d39adf50dc..ea3ed40d0370 100644 --- a/drivers/firmware/dmi_scan.c +++ b/drivers/firmware/dmi_scan.c @@ -10,6 +10,9 @@ #include #include #include +#if IS_ENABLED(CONFIG_OF) +#include +#endif #ifndef SMBIOS_ENTRY_POINT_SCAN_START #define SMBIOS_ENTRY_POINT_SCAN_START 0xF0000 @@ -670,6 +673,70 @@ static int __init dmi_smbios3_present(const u8 *buf) return 1; } +#if IS_ENABLED(CONFIG_OF) +/** + * dmi_scan_from_dt - Find and parse DMI/SMBIOS tables from the Device Tree + * + * Checks if the bootloader has passed SMBIOS table addresses via the /chosen + * node in the Device Tree. This follows the standard kernel DT bindings and + * assumes a fixed 32-byte mapping for the entry point. + * Returns true if a valid table is found and successfully parsed. + */ +static bool __init dmi_scan_from_dt(void) +{ + struct device_node *chosen; + const __be64 *prop; + char buf[32]; + void __iomem *p; + bool dmi_available = false; + u64 addr; + int len; + + chosen = of_find_node_by_path("/chosen"); + if (!chosen) + return false; + + /* SMBIOSv3 (64-bit entry point) has priority */ + prop = of_get_property(chosen, "linux,smbios3-table", &len); + if (prop && len >= sizeof(u64)) { + addr = be64_to_cpup(prop); + + p = dmi_early_remap(addr, 32); + if (p == NULL) + goto out; + + memcpy_fromio(buf, p, sizeof(buf)); + dmi_early_unmap(p, 32); + + if (!dmi_smbios3_present(buf)) { + dmi_available = true; + goto out; + } + } + + prop = of_get_property(chosen, "linux,smbios-table", &len); + if (prop && len >= sizeof(u64)) { + addr = be64_to_cpup(prop); + + p = dmi_early_remap(addr, 32); + if (p == NULL) + goto out; + + memcpy_fromio(buf, p, sizeof(buf)); + dmi_early_unmap(p, 32); + + if (!dmi_present(buf)) + dmi_available = true; + } + +out: + of_node_put(chosen); + return dmi_available; +} +#else +static bool __init dmi_scan_from_dt(void) { return false; } +#endif /* IS_ENABLED(CONFIG_OF) */ + static void __init dmi_scan_machine(void) { char __iomem *p, *q; @@ -718,6 +785,13 @@ static void __init dmi_scan_machine(void) dmi_available = 1; return; } + } else if (IS_ENABLED(CONFIG_OF) && dmi_scan_from_dt()) { + /* + * If EFI is not present or failed, try getting SMBIOS + * tables from the Device Tree. + */ + dmi_available = 1; + return; } else if (IS_ENABLED(CONFIG_DMI_SCAN_MACHINE_NON_EFI_FALLBACK)) { p = dmi_early_remap(SMBIOS_ENTRY_POINT_SCAN_START, 0x10000); if (p == NULL)